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GPS
25-Nov-2009, 04:47
I have decided to start a new thread about the well known focusing problem with Chamonix 45N-1 camera so as not to discuss it in threads not fully related to it.
Here is the announcement of the problem together with its solutions (taken from Chamonix cameras website):

Announcement from Chamonix view camera regarding Fresnel lens problem of 45N-1
After repeated testing, it has been confirmed that the Fresnel lens of our 45n-1 cameras will cause focus shift of various degrees when used with certain lenses. The main cause of this problem is that the Fresnel lens is a convex lens with rounded bands; it has its own unique focusing and other characteristics. When you place a Fresnel lens between a ground glass and a lens, it may cause some kind of distortion of the light coming from the lens.
This is a very old problem. Past and current manufacturers of view cameras all have to deal with this problem. Different manufacturers have chosen different solutions to this problem:
1. Some manufacturers like Sinar use Fresnel lenses that can be taken off. This is due to the fact that a very large part of Sinar view cameras are used for commercial photography where large apertures are frequently used. 2. Some manufacturers put the Fresnel lens behind the ground glass. This solution avoids the problem of focus shift, but causes another problem: damages and scratches of the Fresnel lens as it is made of soft materials prone to scratches. 3. Some manufacturers use a Fresnel lens that has a small area in the middle that is transparent and non- magnifying to avoid the problem. 4. Majority manufacturers will tolerate this focus drift by putting the Fresnel lens in front of the ground glass. 5. Some manufacturers like Ebony use a special piece of glass which combines the Fresnel lens and ground glass into one.
In the design stage of 45N-1 camera, we did not plan to put a Fresnel lens on it. When the prototype of 45n-1 camera came to light, so many potential users asked that we put a Fresnel lens on the camera as a standard feature. So we decided to add a Fresnel lens to the 45N-1 camera. Before the production, I made a trip to Japan just to purchase the special ground glass with build-in Fresnel lens like the one Ebony uses. But manufacturers of these special screens in Japan refused to supply us for reasons unknown, maybe for fear of competition. So we had no other options but to choose to tolerate the problem of possible focus shift with certain lenses.
In my experience and from what I have learned from test results, it seems that lenses of different structure and lenses of different focal lengths will have different focus shift when used with Fresnel lenses. Certain lenses, for example, will produce slight focus shift when stopping down due to their unique structure of the lens. Based on this, I do not recommend that users of 45N-1 camera to change the position of the Fresnel lens as all cameras are tested for the accuracy of the Fresnel position before leaving our factory. By changing the position of Fresnel lens, one can’t solve the focus shift problem for all the lenses, only some of the lenses.
My recommendation for those of you who have this focus shift problem is the following:
1. Take off the Fresnel lens and use your camera as usual. 2. Return your focus screen to your dealer and our factory will modify it by drilling a hole of 16mm diameter in the middle of the Fresnel lens. This small hole can prevent or fix focus shift that may or has occurred. We have done repeated tests with this method and the result is very satisfactory. The small hole will not interfere with your composition on the ground glass and will easily prevent possible focus shift.
For all 45N-1 camera users, I sincerely apologize for this design error caused by my improper judgment. This warns us to be more careful in future and we will fix this error. For future 45n models, this 16mm hole on the Fresnel lens will be standard.
Hass

What is interesting on this announcement is the way how Chamonix tries at the same time to announce “we made a constructional mistake on our camera” and to induce in the reader a thought that the same mistake is found on other cameras too. Also, the whole text is ridden with technically incorrect statements.
Take the first paragraph – Chamonix doesn't say truth about their technical mistake. The cause of the focusing error on their 45N-1 camera is the fact that, originally, the camera was made with a ground glass focusing screen only. When Fresnel lens was added (causing a focus shift) the position of this sandwich in relation to the film plane was not changed thus adding a focusing error to the camera. The error is therefore made by leaving the gg-film plane distance unchanged.
But in their explanation Chamonix puts 2 different causes on the same level – the Fresnel lens focus shift in itself and the omission of Chamonix constructor to take it into account. Chamonix wants us to believe that their original mistake is due to the Fresnel lens characteristic and not their own omission. The two things are in fact different.
The different focus shift in Fresnel lens (due to the different focal lengths of taking lenses) is not of the same nature (and it is much smaller) as the original incorrect focusing distance introduced to their camera by not taking Fresnel in account at all.

Then the incorrect logic continues. n.1) Sinar has the removable Fresnel screen on the external side, not the internal one as the Chamonix camera in question. Therefore this screen is not removable in order to avoid a focusing error like the one present in Chamonix camera, contrarily to Chamonix instigation!
n.4) The majority of manufacturers tolerate this focus drift – or so Chamonix says. Wrong – the majority (except Chamonix) puts the Fresnel + gg sandwich to the correct focusing distance from the film plane in the first place. What is then tolerated then is the much smaller (in many cases not detectable) focus shift due to the different focal lengths of taking lenses. And even this shift is sometimes taken care of using different Fresnel screens for different focal lengths…
Then Chamonix steers us to believe that they became a victim of a Japanese manufacture who didn’t want to sell them their Fresnel + gg sandwich – “So we had no other options but to choose to tolerate the problem of possible focus shift with certain lenses”. What a pathetic lie! As if Chamonix couldn't focus their Fresnel + gg on their cameras correctly because of that!
And the incorrect mixing of two different focus shift causes goes on in Chamonix announcement – pathetically, Chamonix doesn’t recommend removing the incorrectly focused Fresnel lens because different lenses cause a different focus shift anyway… But what about the focus shift caused by incorrect Fresnel + gg positioning on this camera in the first place? Not a one word about it yet! So much to the honesty of Chamonix manufacturer… ”By changing the position of Fresnel lens, one can’t solve the focus shift problem for all the lenses, only some of the lenses” says Chamonix. Surely not, but you can put the sandwich in question to the right distance in the first place, letting then different focal lengths have their own (smaller) focus shift.
Only at the end, the writer – after leading us to believe that all sandwiched combinations have this error – suddenly apologizes for “this design error caused by my improper judgment”. Well, a design error? Surely. But what about the erroneous explanations afterward?

Darin Boville
25-Nov-2009, 08:58
Hey GPS,

Have we ever established if you own a Chamonix?

--Darin

Jeremy Moore
25-Nov-2009, 09:04
Hey GPS,

Have we ever established if you own a Chamonix?

--Darin

I am kinda curious of the same thing. I own a Chamonix and I don't care anywhere near as much as GPS does. I moved the fresnel behind the GG, problem solved.

SW Rick
25-Nov-2009, 10:08
I am kinda curious of the same thing. I own a Chamonix and I don't care anywhere near as much as GPS does. I moved the fresnel behind the GG, problem solved.

Amen! I have a hard time understanding the holy war- the sheer number of "anti-" posts is overwhelming. What's been said has been said over and over- must it be repeated ad nauseam?

Songyun
25-Nov-2009, 10:16
geez, this guy is obsessed with Chamonix.
The fact that he doesn't own a chamonix camera makes me wonder either he has personal grudge with Hugo, or he has business interest agains Chamonix, or simply he need to GET A LIFE.

BarryS
25-Nov-2009, 10:19
http://img21.imageshack.us/img21/2044/dony0.jpg

pocketfulladoubles
25-Nov-2009, 11:31
I think the bottom line is that the camera is about $800, and for $300 you can put a Maxwell screen for a grand total of $1100 - problem solved. Is this camera with that screen worth $1100? Absolutely, anyday, anywhere. This is a non-issue and waste of typing.

Jay Wolfe
25-Nov-2009, 11:44
I have decided to start a new thread about the well known focusing problem with Chamonix 45N-1 camera so as not to discuss it in threads not fully related to it.
Here is the announcement of the problem together with its solutions (taken from Chamonix cameras website):

Announcement from Chamonix view camera regarding Fresnel lens problem of 45N-1
After repeated testing, it has been confirmed that the Fresnel lens of our 45n-1 cameras will cause focus shift of various degrees when used with certain lenses. The main cause of this problem is that the Fresnel lens is a convex lens with rounded bands; it has its own unique focusing and other characteristics. When you place a Fresnel lens between a ground glass and a lens, it may cause some kind of distortion of the light coming from the lens.
This is a very old problem. Past and current manufacturers of view cameras all have to deal with this problem. Different manufacturers have chosen different solutions to this problem:
1. Some manufacturers like Sinar use Fresnel lenses that can be taken off. This is due to the fact that a very large part of Sinar view cameras are used for commercial photography where large apertures are frequently used. 2. Some manufacturers put the Fresnel lens behind the ground glass. This solution avoids the problem of focus shift, but causes another problem: damages and scratches of the Fresnel lens as it is made of soft materials prone to scratches. 3. Some manufacturers use a Fresnel lens that has a small area in the middle that is transparent and non- magnifying to avoid the problem. 4. Majority manufacturers will tolerate this focus drift by putting the Fresnel lens in front of the ground glass. 5. Some manufacturers like Ebony use a special piece of glass which combines the Fresnel lens and ground glass into one.
In the design stage of 45N-1 camera, we did not plan to put a Fresnel lens on it. When the prototype of 45n-1 camera came to light, so many potential users asked that we put a Fresnel lens on the camera as a standard feature. So we decided to add a Fresnel lens to the 45N-1 camera. Before the production, I made a trip to Japan just to purchase the special ground glass with build-in Fresnel lens like the one Ebony uses. But manufacturers of these special screens in Japan refused to supply us for reasons unknown, maybe for fear of competition. So we had no other options but to choose to tolerate the problem of possible focus shift with certain lenses.
In my experience and from what I have learned from test results, it seems that lenses of different structure and lenses of different focal lengths will have different focus shift when used with Fresnel lenses. Certain lenses, for example, will produce slight focus shift when stopping down due to their unique structure of the lens. Based on this, I do not recommend that users of 45N-1 camera to change the position of the Fresnel lens as all cameras are tested for the accuracy of the Fresnel position before leaving our factory. By changing the position of Fresnel lens, one can’t solve the focus shift problem for all the lenses, only some of the lenses.
My recommendation for those of you who have this focus shift problem is the following:
1. Take off the Fresnel lens and use your camera as usual. 2. Return your focus screen to your dealer and our factory will modify it by drilling a hole of 16mm diameter in the middle of the Fresnel lens. This small hole can prevent or fix focus shift that may or has occurred. We have done repeated tests with this method and the result is very satisfactory. The small hole will not interfere with your composition on the ground glass and will easily prevent possible focus shift.
For all 45N-1 camera users, I sincerely apologize for this design error caused by my improper judgment. This warns us to be more careful in future and we will fix this error. For future 45n models, this 16mm hole on the Fresnel lens will be standard.
Hass

What is interesting on this announcement is the way how Chamonix tries at the same time to announce “we made a constructional mistake on our camera” and to induce in the reader a thought that the same mistake is found on other cameras too. Also, the whole text is ridden with technically incorrect statements.
Take the first paragraph – Chamonix doesn't say truth about their technical mistake. The cause of the focusing error on their 45N-1 camera is the fact that, originally, the camera was made with a ground glass focusing screen only. When Fresnel lens was added (causing a focus shift) the position of this sandwich in relation to the film plane was not changed thus adding a focusing error to the camera. The error is therefore made by leaving the gg-film plane distance unchanged.
But in their explanation Chamonix puts 2 different causes on the same level – the Fresnel lens focus shift in itself and the omission of Chamonix constructor to take it into account. Chamonix wants us to believe that their original mistake is due to the Fresnel lens characteristic and not their own omission. The two things are in fact different.
The different focus shift in Fresnel lens (due to the different focal lengths of taking lenses) is not of the same nature (and it is much smaller) as the original incorrect focusing distance introduced to their camera by not taking Fresnel in account at all.

Then the incorrect logic continues. n.1) Sinar has the removable Fresnel screen on the external side, not the internal one as the Chamonix camera in question. Therefore this screen is not removable in order to avoid a focusing error like the one present in Chamonix camera, contrarily to Chamonix instigation!
n.4) The majority of manufacturers tolerate this focus drift – or so Chamonix says. Wrong – the majority (except Chamonix) puts the Fresnel + gg sandwich to the correct focusing distance from the film plane in the first place. What is then tolerated then is the much smaller (in many cases not detectable) focus shift due to the different focal lengths of taking lenses. And even this shift is sometimes taken care of using different Fresnel screens for different focal lengths…
Then Chamonix steers us to believe that they became a victim of a Japanese manufacture who didn’t want to sell them their Fresnel + gg sandwich – “So we had no other options but to choose to tolerate the problem of possible focus shift with certain lenses”. What a pathetic lie! As if Chamonix couldn't focus their Fresnel + gg on their cameras correctly because of that!
And the incorrect mixing of two different focus shift causes goes on in Chamonix announcement – pathetically, Chamonix doesn’t recommend removing the incorrectly focused Fresnel lens because different lenses cause a different focus shift anyway… But what about the focus shift caused by incorrect Fresnel + gg positioning on this camera in the first place? Not a one word about it yet! So much to the honesty of Chamonix manufacturer… ”By changing the position of Fresnel lens, one can’t solve the focus shift problem for all the lenses, only some of the lenses” says Chamonix. Surely not, but you can put the sandwich in question to the right distance in the first place, letting then different focal lengths have their own (smaller) focus shift.
Only at the end, the writer – after leading us to believe that all sandwiched combinations have this error – suddenly apologizes for “this design error caused by my improper judgment”. Well, a design error? Surely. But what about the erroneous explanations afterward?


Grump. Get a life.

eddie
25-Nov-2009, 11:50
Hey GPS,

Have we ever established if you own a Chamonix?

--Darin


I am kinda curious of the same thing. I own a Chamonix and I don't care anywhere near as much as GPS does. I moved the fresnel behind the GG, problem solved.


Amen! I have a hard time understanding the holy war- the sheer number of "anti-" posts is overwhelming. What's been said has been said over and over- must it be repeated ad nauseam?


geez, this guy is obsessed with Chamonix.
The fact that he doesn't own a chamonix camera makes me wonder either he has personal grudge with Hugo, or he has business interest agains Chamonix, or simply he need to GET A LIFE.


http://img21.imageshack.us/img21/2044/dony0.jpg


Grump. Get a life.

har har har!

thanks for the laugh guys!

my chamonix works great. i love it!

iamjanco
25-Nov-2009, 12:43
I own a closet full of Charmin (which is spelled somewhat like Chamonix), which tends to come to mind when I read the first post in this thread. I gotta admit though that the whole Chamonix thing has put me somewhat off their products. I guess if I already owned one, I might feel different, but I probably wouldn't be overjoyed about the situation. And if that were the case, I'd most likely would still be able to sleep at night.

Michael Gordon
25-Nov-2009, 12:47
Easy fix, guys. Just quit shooting so damn wide :D

gregvds
25-Nov-2009, 12:53
Haha Michael Gordon,

That's so true.

Anyway, mine is ordered, and Hugo will put the fresnel on top of the GG, so for me, they have a tech solution they can implement readily, and will for mine, so no prob. I'll see with time and living with if a Beattie or Maxwell could be interesting. We'll see.

Greg

Darin Boville
25-Nov-2009, 13:40
You own a closet full of Charmin? How many rolls is that? 200? 300?

Inquiring minds want to know :)

--Darin

GPS
26-Nov-2009, 05:36
Hmm. Seems that religious feelings run high in this thread. But none of them answers the OP's final question...

Marko
26-Nov-2009, 09:56
Hmm. Seems that religious feelings run high in this thread. But none of them answers the OP's final question...

The only question I remember was: do YOU own a Chamonix?

Well, do you?

Jason Greenberg Motamedi
26-Nov-2009, 10:08
Focus errors on a Fresnel lens are an easy fix; just replace it. For what it is worth, the Fresnel on my 5x7 Canham, which was a very early issue, had focus errors. I replaced it with a BosScreen and have never regretted it.

gregvds
26-Nov-2009, 15:27
Jason,

Do you know if bosscreen are still available these days?

Thanks,

GPS
26-Nov-2009, 17:06
Focus errors on a Fresnel lens are an easy fix; just replace it. For what it is worth, the Fresnel on my 5x7 Canham, which was a very early issue, had focus errors. I replaced it with a BosScreen and have never regretted it.

Agreed - fixing the Fresnel lens focus error is not so difficult technically as I already said in Greg's "Leave Wista for Chamonix..." thread. But business-wise it's a different thing as we can see in this specific case.
Also, the Bosscreen would need to have the appropriate Chamonix glass thickness to be error-free in itself...

Brian Ellis
26-Nov-2009, 18:03
Jason,

Do you know if bosscreen are still available these days?

Thanks,

I'm not Jason but I've been told they aren't. However, I haven't searched for one myself lately. If he's still in business a call or email to Ted Bromwell of Bromwell Marketing would tell you for sure if nobody here knows for sure. If they're gone that's too bad, IMHO they were the best screen out there except for the Maxwell. I used them on four or five different cameras including an 8x10 Deardorff.

Brian Ellis
26-Nov-2009, 18:18
Hmm. Seems that religious feelings run high in this thread. But none of them answers the OP's final question...

Speaking for myself, the answer is that the Chamonix I owned was the best combination of camera/value-for-the money of any of the 11 LF cameras I've owned and in absolute terms it was the best wooden camera at any price of any of the 8 wooden cameras I've owned, which includes two Ebonys that cost three times as much as the Chamnonix. So to me the focus error with which the OP appears to be obsessed is IMHO insignificant. As someone else pointed out, you could spend another $300 on a Maxwell screen if you didn't like any other solution and for $1,100 you'd have a great camera with the best screen available at what to me would still be a bargain price.

iamjanco
27-Nov-2009, 06:20
You own a closet full of Charmin? How many rolls is that? 200? 300?

It's got to be at least a couple of hundred. But I won't go through the motion of calculating the closet size, the approx. size of each cylinder, nor will I subtract the volume the shelving takes up. And, if it really was true, I wouldn't explain why one might see any need or wealth in owning a couple of hundred rolls of an item that, when missed, some might consider worth its weight in gold.

Instead, I'll just share a photo I found on Wikipedia that illustrates how far we, as a species, have come along through the ages:

http://upload.wikimedia.org/wikipedia/commons/4/4b/Nara_period_toilet_paper.jpg
Wooden toilet paper from the Nara period (710 to 784) in Japan. The modern rolls in the background are for size comparison.

...note to Jan: I've got to get a life ;)

Jan C.

GPS
27-Nov-2009, 15:48
...
Well, a design error? Surely. But what about the erroneous explanations afterward?


Speaking for myself, the answer is that the Chamonix I owned was the best combination of camera/value-for-the money of any of the 11 LF cameras I've owned and in absolute terms it was the best wooden camera at any price of any of the 8 wooden cameras I've owned, which includes two Ebonys that cost three times as much as the Chamnonix. So to me the focus error with which the OP appears to be obsessed is IMHO insignificant. As someone else pointed out, you could spend another $300 on a Maxwell screen if you didn't like any other solution and for $1,100 you'd have a great camera with the best screen available at what to me would still be a bargain price.

Brian,
opinions about the "best camera" varies as much as persons individual taste. None of that opinion answers the OP's question.
If now you think that to ignore the focus error is the solution of it I have to say that Chamonix was more clever than that. After suggesting this "solution" it soon realized it wouldn't work with customers...
Also buying a $300 Maxwell screen to complete the Chamonix camera is hardly an attractive solution for them either.
But the question was not about a solution of the technical problem. So it still remains unanswered...

Darin Boville
27-Nov-2009, 16:50
>After suggesting this "solution" it soon realized it wouldn't work with customers...<<

Hey GPS,

So let me get this straight. You don't own a Chamonix camera. You are, instead, a public representative for me, the customer. Do I have that right?

--Darin

pocketfulladoubles
27-Nov-2009, 19:33
Also buying a $300 Maxwell screen to complete the Chamonix camera is hardly an attractive solution for them either.

Really, because I did just that and it is a very good camera for the money - still. I'm curious why you think this would not be a good solution? People put these screens on far more expensive cameras, so why not the Chamonix?

Curt Palm
27-Nov-2009, 21:53
Brian,
opinions about the "best camera" varies as much as persons individual taste. None of that opinion answers the OP's question.
If now you think that to ignore the focus error is the solution of it I have to say that Chamonix was more clever than that. After suggesting this "solution" it soon realized it wouldn't work with customers...
Also buying a $300 Maxwell screen to complete the Chamonix camera is hardly an attractive solution for them either.
But the question was not about a solution of the technical problem. So it still remains unanswered...

isn't the OP GPS? why the third person references?

Patrick Dixon
28-Nov-2009, 06:36
Instead, I'll just share a photo I found on Wikipedia that illustrates how far we, as a species, have come along through the ages:


I assumed that was a photo of what GPS had done to his Chamonix camera in disgust .... then I remembered that he doesn't actually own one.

Jeremy Moore
28-Nov-2009, 07:16
Where does one buy a Bill Maxwell screen. A simple Google search turned up nothing.

lilmsmaggie
28-Nov-2009, 07:33
You'll probably have to drop him a line:

Maxwell Precision Optics
PO Box 33146
Decatur, GA 30033-0146
(404) 244-0095

pocketfulladoubles
28-Nov-2009, 08:24
Where does one buy a Bill Maxwell screen. A simple Google search turned up nothing.

You call him directly. Expect a good discussion in optics, and then you can order it.

Jeffrey Sipress
28-Nov-2009, 10:21
WARNING: While Bill's screens are great, he will chew your ear off for hours on the phone, and it is very difficult to end the 'conversation'. Make sure you have plenty of time to kill, or fake some sort of emergency to get off the phone.

Jeremy Moore
28-Nov-2009, 10:28
WARNING: While Bill's screens are great, he will chew your ear off for hours on the phone, and it is very difficult to end the 'conversation'. Make sure you have plenty of time to kill, or fake some sort of emergency to get off the phone.

I'm planning on having it ordered for me as an XMas present. I'll give them the particulars and they can call :D

lenicolas
28-Nov-2009, 11:47
hi,
in your own experience, when does this focusing problem occurs?
i understand that it's only with wide lenses...
I just ordered a 135mm, should i pay extra attention?

rugenius
28-Nov-2009, 13:27
A large format short focal length lens is generally "wide" so that it can take advantage of the film real estate available. Having said that, the fresnel lens thickness and angular aperture of the taking lens are basic optical properties that determine how much shift is induced away from the film plane (properly and normally established by the GG plane as you adjust focusing and develop an image at the GG).
I don't know which 135 mm focal length lens you are referring to...
You probably have some noticeable error depending on the 135 mm lens in question. But I believe it is more dependent on the half angle from lens aperture to film/GG plane.
There are other factors to take into account such as how much of what you are shooting is intended to be in focus, Ex infinity vs macro work.
But this is all moot anyway if you just remove the fresnel, or place it between you and GG, or replace the stock fresnel with some other screen intensifier.
It's really not as big a deal as many people have made it out to be.

If your work requires the use of lenses and situations that develop problems with the stock Chamonix fresnel/ screen intensifier... then you will want to invest a bit more in accessories to accomplish your tasks.
That said,... since you don't know yet... why invent a problem...:)

Bob Salomon
28-Nov-2009, 14:48
"But this is all moot anyway if you just remove the fresnel, or place it between you and GG, or replace the stock fresnel with some other screen intensifier.
It's really not as big a deal as many people have made it out to be."

Yes it can be a very big deal if the camera designer designed the fresnel to be in front of the gg. If you just take the fresnel out and put it on top of the gg or just replace it with another behind the gg or just throw the fresnel away you will probably need the ground position of the gg adjusted as it expected a spacer the thickness of the original fresnel lens.

Mike1234
28-Nov-2009, 14:53
Bob, that is the problem with the Chamonix 4x5. They failed to take the thickness of the fresnel into account thereby throwing the focus position that far off straight from the factory. The end-user "solution" is to move the fresnel behind the GG... not an appropriate resolution, IMO.

Peter K
28-Nov-2009, 16:07
It's really not as big a deal as many people have made it out to be.
No it's not a big deal if one calculates the total focal-lenght of the combination of taking lens and fresnel-lens but also for every distance between the two lenses. The thickness of the fresnel-lens leave no remainder.

An auxilary lens, either a diopter-lens or a fresnel-lens, changes the total focal-lenght of the optical system, depending not only on the focal-lenghts of the two lenses - in this case the taking lens and the fresnel-lens - but also on the distance between the two lenses.

The correct formula is f_t= 1/( 1/f_m + 1/f_fl + d/f_m*f-fl), where the f_m is the focal-lengt of the main taking-lens and f_fl is the focal-lenght of the fresnel-lens, f_t is total focal length, and d is a spacing correction factor.

If a fresnel-lens is used before the ground-glass, it's influence is bigger as shorter the distance between the two lenses. So the focussing error is larger with WA-lenses focussed at infinity as with long focal-lenghts or long bellows-extentions.

To avoid all this calculations place the fresnel-lens behind the ground-glass.

Peter

Michael Rosenberg
28-Nov-2009, 16:13
"But this is all moot anyway if you just remove the fresnel, or place it between you and GG, or replace the stock fresnel with some other screen intensifier.
It's really not as big a deal as many people have made it out to be."

Yes it can be a very big deal if the camera designer designed the fresnel to be in front of the gg. If you just take the fresnel out and put it on top of the gg or just replace it with another behind the gg or just throw the fresnel away you will probably need the ground position of the gg adjusted as it expected a spacer the thickness of the original fresnel lens.

Bob,

This was already discussed in previous threads. The Chamonix fresnel lies in a recess below the gg - in other words the gg sits on ledges above the fresnel and does not rest on the fresnel. You can remove the fresnel in this camera and it does not affect the position of the gg. At All. Notta.

Mike

rugenius
28-Nov-2009, 18:18
Michael Rosenberg wrote: "You can remove the fresnel in this camera and it does not affect the position of the gg. At All. Notta..."

Thanks!!
Mike,... finally someone who gets it.

I imagine enough people that have griped about the issue hadn't realized that the GG position does not change because they may not even own one of these cameras.

No matter the current apology and explanation given by Chamonix...
My guess is,... maybe,... way back... Chamonix simply chose to protect the fresnel from scratches by placing it in front and had not considered how much of a fiasco they might have created... even if other manufacturers had done the same.

If they had stuck with the GG, and offered the fresnel purely as an accessory with a disclaimer involving fresnel thickness and focus shift with wide angle lenses of XXX mm and XX or greater angular aperture they would have saved everyone including themselves the headache of admitting to some sort of "design flaw".
And,... I'll bet people would have still bought the Chamonix fresnel/ screen intensifier because it would have been much cheaper than a new Maxwell screen.

Larry Gebhardt
28-Nov-2009, 18:27
No it's not a big deal if one calculates the total focal-lenght of the combination of taking lens and fresnel-lens but also for every distance between the two lenses. The thickness of the fresnel-lens leave no remainder.

An auxilary lens, either a diopter-lens or a fresnel-lens, changes the total focal-lenght of the optical system, depending not only on the focal-lenghts of the two lenses - in this case the taking lens and the fresnel-lens - but also on the distance between the two lenses.

The correct formula is f_t= 1/( 1/f_m + 1/f_fl + d/f_m*f-fl), where the f_m is the focal-lengt of the main taking-lens and f_fl is the focal-lenght of the fresnel-lens, f_t is total focal length, and d is a spacing correction factor.

If a fresnel-lens is used before the ground-glass, it's influence is bigger as shorter the distance between the two lenses. So the focussing error is larger with WA-lenses focussed at infinity as with long focal-lenghts or long bellows-extentions.

To avoid all this calculations place the fresnel-lens behind the ground-glass.

Peter

Peter, thanks for that explanation. I finally see why when I tested my 75 and 90mm lenses I could find no focus error. I was testing at very close distances, so the lens was extended quite a bit. Probably more than my 135mm at infinity. Must have masked the error. However I have taken over a hundred sheets with the Chamonix and have yet to see an issue in the real world, even on shots using the 75mm (always stopped down to at least f/16).

Has anyone tested moving the fresnel behind the ground glass and then putting a thin cover sheet of glass over that (a fresnel sandwich so to speak)? Seems like it would fix the problem and protect the fresnel.

Darin Boville
28-Nov-2009, 19:39
I have taken over a hundred sheets with the Chamonix and have yet to see an issue in the real world

Come to think of it, in all the threads about this issue and all the negative posts I don't think I've seen a sample image showing the problem.

--Darin

Jeffrey Sipress
28-Nov-2009, 19:54
I think it's vaporware.

gregvds
29-Nov-2009, 00:22
So, let's stop posting here, and let the subject sink to nowhere.
I'll make a new thread to show you my future 45N-1 :-).

GPS
29-Nov-2009, 04:47
Really, because I did just that and it is a very good camera for the money - still. I'm curious why you think this would not be a good solution? People put these screens on far more expensive cameras, so why not the Chamonix?

While you can put a Maxwell screen on any camera you can hardly ask people to buy a $ 300 screen to put on a Chamonix camera as a solution of the design flaw the camera was bought with - not with common sens. Not even Chamonix has the courage to ask that - and they propose several solutions of their manufacturing shortcoming. What is more, the Maxwell screen still needs to be positioned properly to the right focusing registration on the camera back...

John T
29-Nov-2009, 08:21
So, let's stop posting here, and let the subject sink to nowhere.
I'll make a new thread to show you my future 45N-1 :-).

But GPS will use his gps and find that thread and ruin it also. Maybe it can be restricted to just us 45N owners ;^)

Jeremy Moore
29-Nov-2009, 13:07
While you can put a Maxwell screen on any camera you can hardly ask people to buy a $ 300 screen to put on a Chamonix camera as a solution of the design flaw the camera was bought with - not with common sens. Not even Chamonix has the courage to ask that - and they propose several solutions of their manufacturing shortcoming. What is more, the Maxwell screen still needs to be positioned properly to the right focusing registration on the camera back...

Is this what you did with your Chamonix? Oh, wait... you don't own one, you're just a competitor or someone with a grudge as far as we can tell.

SW Rick
29-Nov-2009, 13:51
Is this what you did with your Chamonix? Oh, wait... you don't own one, you're just a competitor or someone with a grudge as far as we can tell.

Could be because Hugo didn't laugh at his jokes at the party?

Mike1234
29-Nov-2009, 15:30
I'm not trying to argue here but I just want to express my opinion. If something has a flaw I'm not going to pay full price for it. I don't want to move the fresnel to the back of the GG because then it's unprotected.

If there's a fly in my soup I'm sending it back and going to a different restaurant especially if there's a fly in every order delivered. The fly is very small and insignificant when compared to the full bowl of soup but it's still a fly. I could pick it out myself, as could all the other guests, but then there's still residual fly (whatever) in the soup and it's not what we were promised. I'm getting my money back and will never eat there again.

No, I don't have a Chamonix 4x5 nor will I buy one until the issue is resolved at the factory unless they sell it at a discount or unless I find one used cheap enough to somewhat offset the price of a relacement screen.

FWIW, I like the Chamonix 4x5... a LOT!! But I liked that restaurant's soup too.

Larry Gebhardt
29-Nov-2009, 15:41
Mike, I agree with you. However, I currently have the camera and have little chance of a refund since I bought it used. So I will just try to enjoy my soup after I pick out the fly.

I do think the factory's response is disappointing. However I imagine it would be too costly for them to replace all the backs out there, especially for an issue that doesn't show up in normal shots. I also don't understand why people are so hostile to GPS for bringing this up, as it is a real issue, and the factory response is lacking by western standards.

Mike1234
29-Nov-2009, 15:56
It's really, really, good soup, Larry, and you've already removed the fly. From everything I've read I'm convinced this is the camera for me. I'm just waiting and holding my breath............ for either a factory fix, discount on a new one sans screen, or a good deal on a used one.

Jeffrey Sipress
29-Nov-2009, 17:38
I own a Chamonix for about a year, and have no focusing problems. I typically use lenses from 90 to 300mm.

Mike1234
29-Nov-2009, 17:40
Well, if the wider lenses truly make the problem worse then it makes a big difference to me because my widest lens is a 38mm.

vinny
29-Nov-2009, 18:00
Come to think of it, in all the threads about this issue and all the negative posts I don't think I've seen a sample image showing the problem.

--Darin

there are folks that say they've shot tons of film with the camera and had no problems but they don't say that they've done a proper test. For example: I shot hundreds of sheets with first 4x5 camera I had and thought it was great w/o any problems until I saw someone else's very sharp prints and then read an article about ground glass alignment. I measured the depth of mine and found that it was off by a ton (1/16") All those negs that could have been so much sharper if I had only tested my gear and shimmed the gg initially. From then on my work was sharper and not by stopping the lens down further.

I tested my chamonix with a fujinon focus chart at a close distance (4ft) using a 90mm nikkor 4.5. There was measurable distance between the bellows draw with the fresnel in place and without. I took images in both situations, wide open. I have removed the fresnel. I won't be putting in back in with or without a hole drilled in it!

Marko
29-Nov-2009, 18:10
Mike, I agree with you. However, I currently have the camera and have little chance of a refund since I bought it used. So I will just try to enjoy my soup after I pick out the fly.

I do think the factory's response is disappointing. However I imagine it would be too costly for them to replace all the backs out there, especially for an issue that doesn't show up in normal shots. I also don't understand why people are so hostile to GPS for bringing this up, as it is a real issue, and the factory response is lacking by western standards.

Larry, what you are saying makes a lot of sense. The whole thing is disappointing and unfortunate.

But... while the factory response may indeed be lacking by western standards, so is their price! If that very same camera were made in the west, it would easily cost upward of three times the current price. Western prices are higher because western labor is more expensive and as a result, western customers also have more stringent expectations and that, finally, gets factored back into the western prices as well.

Having to deal with an occasional issue like this is the price of buying cheap(er) - buyers who are too distinguishing to accept this should buy an Ebony or a Canham.

The apparent hostility, IMO, comes from the fact that the OP does not even own a Chamonix camera, much less has the problem in question. Some people simply can't miss an opportunity for some good, old Chinese-bashing.

Mike1234
29-Nov-2009, 18:28
I don't sense any Chinese bashing in the original post. Perhaps the OP just feels passionate about customer service and truth in company dealings with their clients. I don't know but I agree that Chamonix handled this poorly. I won't be buying a Chamonix 4x5 anytime soon (unless I can get a really good deal and buy a new screen) but I would feel the same way no matter what country of origin... Italy, UK, Germany, China, Japan, Korea, USA... it doesn't matter. They messed up and didn't properly deal with it. You have a good point regarding price but (please don't take offense) so what? They can force other companies out of business with ultra-low pricing but they're still making a good profit and should backup their products.

Songyun
29-Nov-2009, 18:45
I don't sense any Chinese bashing in the original post. Perhaps the OP just feels passionate about customer service and truth in company dealings with their clients. I don't know but I agree that Chamonix handled this poorly.


You don't sense any Chinese bashing, coz you haven't follow the whole thing long enough. Anyway, the simplest solution is to remove the fresnel, and sell it to unhappy shen hao customer. That's it. You will get dead accurate focus without the fresnel. If you can not live without a fresnel, and you want dead accurate focus, buy a maxwell. With a fresnel between lens and ground glass no matter how you adjust, there is always some lens that it won't focus very accurate.


I won't be buying a Chamonix 4x5 anytime soon (unless I can get a really good deal and buy a new screen)


Just get yourself a Canham, or Ebony or Philips, then you won't be complaining.

Mike1234
29-Nov-2009, 19:08
You don't sense any Chinese bashing, coz you haven't follow the whole thing long enough.

I don't know... but I'm too tired to read through the whole thread right now.


Just get yourself a Canham, or Ebony or Philips, then you won't be complaining.

Why these companies in particular other than product cost?

stealthman_1
29-Nov-2009, 19:18
Still no photos GPS? At 15 feet a 90mm f5.6 lens wide open has a total DOF of 10 feet on 4X5 film. As well, by my own tests with my 20/15 vision, a 90mm lens, and a 8x loupe, a humans ability to focus exactly on an inch mark on a 4 foot rule is very limited at a mere 15 feet. The real-life implications of this 'issue' are very, very limited. A simple Google search will show you discussions of this 'issue' going back nearly 10 years before Chamonix hit the market. An $800 LF camera by any manufacturer has several more significant issues with precise focus than the fresnel screen. Get over it and go back to looking for dead pixels on your LCD screen.;)

Mike1234
29-Nov-2009, 19:50
But DOField is different from DOFocus. :)

vinny
29-Nov-2009, 22:36
But DOField is different from DOFocus. :)

Exactly!
Now, if everyone knew that.

GPS
30-Nov-2009, 01:44
...
If you can not live without a fresnel, and you want dead accurate focus, buy a maxwell. With a fresnel between lens and ground glass no matter how you adjust, there is always some lens that it won't focus very accurate.




Just get yourself a Canham, or Ebony or Philips, then you won't be complaining.

See p. # 43...

GPS
30-Nov-2009, 02:45
No it's not a big deal if one calculates the total focal-lenght of the combination of taking lens and fresnel-lens but also for every distance between the two lenses. The thickness of the fresnel-lens leave no remainder.

An auxilary lens, either a diopter-lens or a fresnel-lens, changes the total focal-lenght of the optical system, depending not only on the focal-lenghts of the two lenses - in this case the taking lens and the fresnel-lens - but also on the distance between the two lenses.

The correct formula is f_t= 1/( 1/f_m + 1/f_fl + d/f_m*f-fl), where the f_m is the focal-lengt of the main taking-lens and f_fl is the focal-lenght of the fresnel-lens, f_t is total focal length, and d is a spacing correction factor.

If a fresnel-lens is used before the ground-glass, it's influence is bigger as shorter the distance between the two lenses. So the focussing error is larger with WA-lenses focussed at infinity as with long focal-lenghts or long bellows-extentions.

To avoid all this calculations place the fresnel-lens behind the ground-glass.

Peter

Peter,
You can calculate to your heart's delight (and me too I love optical calculations as it is the intellectual part of the magic in Optics) but it won't move the incorrectly put gg registration on Chamonix camera at all - not even the thickness of the slightest shim...:)
Notice also that the OP's question is not about how to correct technically the Chamonix constructional mistake...

Marko
30-Nov-2009, 07:37
Notice also that the OP's question is not about how to correct technically the Chamonix constructional mistake...

So, what exactly is the OP's question then?

The opening post was such a rambling mess that you seem to be the only one who really understands it even though you apparently never owned the camera in question. Could you please simplify it for the rest of us, preferably in a single sentence?

Songyun
30-Nov-2009, 08:35
See p. # 43...

You DON'T OWN one, and you have no idea what the back looks like. Pathetic!

Jeffrey Sipress
30-Nov-2009, 09:55
Lot's of chatter about it, but no one has stated what exactly the constructional error is. If removing the fresnel fixes the problem, then it is the fresnel.

Jeremy Moore
30-Nov-2009, 11:14
Lot's of chatter about it, but no one has stated what exactly the constructional error is. If removing the fresnel fixes the problem, then it is the fresnel.

Jeffrey, it has been stated many times: Removing the fresnel fixes the problem.

The GG is properly positioned.

Peter K
30-Nov-2009, 15:06
You can calculate to your heart's delight (and me too I love optical calculations as it is the intellectual part of the magic in Optics) but it won't move the incorrectly put gg registration on Chamonix camera at all - not even the thickness of the slightest shim...:)
GPS,
of course to solve the problem of the incorrectly put gg registration by calculation the total focal lenght of the compound lens in use, taking lens and fresnel-lens, would be magical thinking. I've only tried to explain the problem by optical calculations.

But to convince Chamonix users who prefers to solve the problem by pushing it away looks like magical thinking too. ;)

GPS
30-Nov-2009, 15:13
GPS,
of course to solve the problem of the incorrectly put gg registration by calculation the total focal lenght of the compound lens in use, taking lens and fresnel-lens, would be magical thinking. I've only tried to explain the problem by optical calculations.

But to convince Chamonix users who prefers to solve the problem by pushing it away looks like magical thinking too. ;)

Absolutely, Peter :)

kev curry
1-Dec-2009, 13:00
....Has anyone tested moving the fresnel behind the ground glass and then putting a thin cover sheet of glass over that (a fresnel sandwich so to speak)? Seems like it would fix the problem and protect the fresnel.

I've been a bit concerned about the fresnel getting scratched up over time so I cut and fitted a thin (0.25mm) sheet of clear Acetate over the fresnel. I stuck it down with two thin strips of clear sellotape...I'm happy! When the acetate gets scratched up its easily replaced and only costs pennies. The difference in brightness with or without the acetate is negligible.

mortensen
1-Dec-2009, 13:10
... a little question in this eeeendless thread (that I somehow find myself following...):

does it matter which way the fresnel is set up, ie. which way the grooves face? cause I already managed to scratch the grooves from the inside of the 45n-1... so I turned it the other way round. haven't shot with the camera the last couple of weeks.

Peter K
1-Dec-2009, 18:19
does it matter which way the fresnel is set up, ie. which way the grooves face?
A fresnellens is so thin, compared with a plan-convex lens of the same size, so it doesn't matter.

Peter

Robert A. Zeichner
1-Dec-2009, 20:00
A fresnellens is so thin, compared with a plan-convex lens of the same size, so it doesn't matter.

Peter

It will shift the image rearward by an amount equal to 1/3 the thickness of the Fresnel. A typical Fresnel is .060" thick. A .020" shift is significant. Film holder depth specs for error in 4x5 is +/- .007" as a point of reference.

Why so many are so forgiving of this error is a mystery to me. With so many ways of making errors in focusing, the errors in film holders, camera standards that move unintentionally during set-up etc., etc., etc., it is vital that ground glass/film plane coincidence is as close to perfect as possible. If you start off with error, it is more likely that any error the operator introduces to the equation will result in unacceptable sharpness.

With hand cameras, the best of breed have always been the ones that hold the film the flattest and in the right plane like Leicas and Rolleis. Why are so many willing to overlook the importance of this in large format?

Jack Dahlgren
1-Dec-2009, 20:47
Film holder depth specs for error in 4x5 is +/- .007" as a point of reference.

If you start off with error, it is more likely that any error the operator introduces to the equation will result in unacceptable sharpness.

With hand cameras, the best of breed have always been the ones that hold the film the flattest and in the right plane like Leicas and Rolleis. Why are so many willing to overlook the importance of this in large format?

Perhaps it is because some people are less concerned about sharpness than you are. Really, I don't think that any of my film holders are within 7/1000ths but if I'm handholding and depending on my rangefinder then I'm close enough. No one is going to sit still long enough for me to do any better.

Why don't rollei's and leica's have ground glass so you can focus them properly?

Ulrich Drolshagen
1-Dec-2009, 23:28
It will shift the image rearward by an amount equal to 1/3 the thickness of the Fresnel. A typical Fresnel is .060" thick. A .020" shift is significant. Film holder depth specs for error in 4x5 is +/- .007" as a point of reference.

Why so many are so forgiving of this error is a mystery to me. With so many ways of making errors in focusing, the errors in film holders, camera standards that move unintentionally during set-up etc., etc., etc., it is vital that ground glass/film plane coincidence is as close to perfect as possible. If you start off with error, it is more likely that any error the operator introduces to the equation will result in unacceptable sharpness.

With hand cameras, the best of breed have always been the ones that hold the film the flattest and in the right plane like Leicas and Rolleis. Why are so many willing to overlook the importance of this in large format?

Peter refers to the post before. The question was: Does the orientation of the fresnel matter? As I understand it, the influence of the fresnel as such is out of question.

Ulrich

Darin Boville
2-Dec-2009, 00:07
Is it time to post photos demonstrating the error? Or haven't we run out of chalk yet? :)

--Darin

mortensen
2-Dec-2009, 00:10
thanks :) - to peter, that is (regarding the question about which way to position the grooves of a fresnel)

r_a_feldman
2-Dec-2009, 10:38
It will shift the image rearward by an amount equal to 1/3 the thickness of the Fresnel. A typical Fresnel is .060" thick. A .020" shift is significant.

If one wants to keep using the fresnel in front of the GG, it seems like you could go to a hobby shop and by a package of 0.020" x 0.100" styrene (for maybe $3) and shim the GG back. If you do this, though, I would suggest testing the focus by laying out a yard stick some distance away from the camera, focusing on the 18" mark, taking a picture, and checking the negative to see where the image is sharply focused. ISTR someone doing this test in an earlier thread.

Bob (who does not own a Chamonix, but who has had to measure and adjust the position of his film holder adapter to match the plane of the GG on his old field camera)

Jeremy Moore
2-Dec-2009, 10:46
If one wants to keep using the fresnel in front of the GG, it seems like you could go to a hobby shop and by a package of 0.020" x 0.100" styrene (for maybe $3) and shim the GG back. If you do this, though, I would suggest testing the focus by laying out a yard stick some distance away from the camera, focusing on the 18" mark, taking a picture, and checking the negative to see where the image is sharply focused. ISTR someone doing this test in an earlier thread.

Bob (who does not own a Chamonix, but who has had to measure and adjust the position of his film holder adapter to match the plane of the GG on his old field camera)

If one wants to keep the fresnel in front of the GG then you're causing yourself headaches and using the above will just cause more. The fresnel causes focus shift that is different based on lens used. Just take out the damn fresnel and throw it away or move it to b/w you and the GG--problem solved. Now let's go back to taking pictures.

Darin Boville
2-Dec-2009, 10:51
...I would suggest testing the focus by laying out a yard stick some distance away from the camera, focusing on the 18" mark, taking a picture, and checking the negative to see where the image is sharply focused. ISTR someone doing this test in an earlier thread.

That was probably me...I haven't seen anyone else post an image in this debate, on this thread or any of the others.

The problem is, people who are seeing a problem--or are hypothesizing one--are saying that the error will only reveal itself with wide angles--90 or wider--and when focused at longer distances. So the ruler test doesn't seem to work.

--Darin

Mike1234
2-Dec-2009, 10:54
After reading this thread and many others it seems that many believe fresnel lenses are actually unnecessary elements that are counter-productive to accurate focusing and often inhibit more than they help. Or am I missing something? So why are they so common if they suck? After reading many posts I get the strong feeling that the fresnel SHOULD be mounted to the outside (viewer side) of the GG and that we should keep an array of different FL fresnels to accomodate specific FL ranges of lenses and the appropriate fresnel should only TEMPORARILY be placed on the GG as needed to compose/focus. Does this sound right to those in the know?

Marko
2-Dec-2009, 11:07
That was probably me...I haven't seen anyone else post an image in this debate, on this thread or any of the others.

The problem is, people who are seeing a problem--or are hypothesizing one--are saying that the error will only reveal itself with wide angles--90 or wider--and when focused at longer distances. So the ruler test doesn't seem to work.

That's what the company itself specified in their press release about the error. Since the OP does not own the camera in question, he can't have that problem and he's not even hypothesizing.

I characterized it as Chinese-bashing earlier because there are people who never miss a good opportunity to bash Chinese, Russian or other non-Western manufacturers (just look past discussions on this forum for examples) and because I don't think the OP would raise equal concern had the manufacturer been from somewhere else (again, based on his own and other past postings).

As noticed, there are no images posted yet, despite all the requests. Given all the noise and indignation, one would expect a flood of images demonstrating the defect by now... ;)

Jeremy Moore
2-Dec-2009, 11:09
Does this sound right to those in the know?

No. Different focal length fresnels only have practical use in very specific situations--situations which I don't believe 99.9% of large format photographers are going to run into.

Some people like fresnels as they find it helpful for focusing and other don't like the concentric rings that come with them--it's a personal preference.

r_a_feldman
2-Dec-2009, 11:10
That was probably me...I haven't seen anyone else post an image in this debate, on this thread or any of the others.

The problem is, people who are seeing a problem--or are hypothesizing one--are saying that the error will only reveal itself with wide angles--90 or wider--and when focused at longer distances. So the ruler test doesn't seem to work.

--Darin

If you can't see any focusing error in an actual test, then (as a number of Chamonix users have said in this thread) there does not seem to be much of a problem.

Bob

Jeremy Moore
2-Dec-2009, 11:16
If you can't see any focusing error in an actual test, then (as a number of Chamonix users have said in this thread) there does not seem to be much of a problem.

Bob

There is a very easy test.

1. Setup camera with 90mm or wider lens.

2. Focus on a mid-distance subject using a high quality loupe and good technique while shooting wide open to exacerbate the issue.

3. Take a picture

4. Remove the fresnel

5. Repeat steps 2 & 3.

6. Develop and compare images.

r_a_feldman
2-Dec-2009, 11:30
There is a very easy test.

1. Setup camera with 90mm or wider lens.

2. Focus on a mid-distance subject using a high quality loupe and good technique while shooting wide open to exacerbate the issue.

3. Take a picture

4. Remove the fresnel

5. Repeat steps 2 & 3.

6. Develop and compare images.

This seems like a good test, but you are going to need a ROCK SOLID tripod so that the camera does not move while you remove the back to take off the fresnel.

Bob

Mike1234
2-Dec-2009, 11:32
So who's going to do the deed?

Jeremy Moore
2-Dec-2009, 11:40
This seems like a good test, but you are going to need a ROCK SOLID tripod so that the camera does not move while you remove the back to take off the fresnel.

Bob

I have a Majestic with 6" bed and can do the shot from inside my apartment onto the balcony to make the weather/wind not an issue. I'll go through the rigmarole and make the test this evening.

Edit: Anyone that may have an issue with how this test is conducted and nitpick it later are given the opportunity--RIGHT NOW--to make suggestions on the testing procedure.

Clement Apffel
2-Dec-2009, 11:44
The problem is, people who are seeing a problem--or are hypothesizing one--are saying that the error will only reveal itself with wide angles--90 or wider--and when focused at longer distances. So the ruler test doesn't seem to work.

--Darin

I observed the issue for the first time with a 150mm f/4.5.
portraits at 4m distance (around 13 feets I believe) wide open.
resulting error is the same on everysingle portrait :
point of focus systematically 1 full meter before the subject.

did tests with the exact same setting and lens but without the fresnel : point of focus was where I set it.

the reason I didn't post image is that we speak of quite fine focus/sharpness difference and those won't appear on a attachable 700x500 dot image.
and I guess I was too lazy to do crops and stuff. ;)
Maybe other users felt the same way.



I characterized it as Chinese-bashing earlier because there are people who never miss a good opportunity to bash Chinese, Russian or other non-Western manufacturers (just look past discussions on this forum for examples) and because I don't think the OP would raise equal concern had the manufacturer been from somewhere else (again, based on his own and other past postings).

Just quoting this to mention that Marko isn't the sole member thinking about that.



Now let's go back to taking pictures.

AAAAnd Amen to that.

Mike1234
2-Dec-2009, 11:50
I have a Majestic with 6" bed and can do the shot from inside my apartment onto the balcony to make the weather/wind not an issue. I'll go through the rigmarole and make the test this evening.

Edit: Anyone that may have an issue with how this test is conducted and nitpick it later are given the opportunity--RIGHT NOW--to make suggestions on the testing procedure.

If you're on the second floor... not on solid ground or concrete foundation... someone will cry foul.

Jeremy Moore
2-Dec-2009, 11:53
So who's going to do the deed?

See this thread (http://www.largeformatphotography.info/forum/showthread.php?p=533158#post533158).

Jeremy Moore
2-Dec-2009, 11:55
If you're on the second floor... not on solid ground or concrete foundation... someone will cry foul.

Good point, I'll light the subject with flash to avoid any motion blur and I'll be sure to shoot from a ground floor to make sure the tripod doesn't move any.

r_a_feldman
2-Dec-2009, 12:13
I observed the issue for the first time with a 150mm f/4.5.
portraits at 4m distance (around 13 feets I believe) wide open.
resulting error is the same on everysingle portrait :
point of focus systematically 1 full meter before the subject.

did tests with the exact same setting and lens but without the fresnel : point of focus was where I set it.

the reason I didn't post image is that we speak of quite fine focus/sharpness difference and those won't appear on a attachable 700x500 dot image.
and I guess I was too lazy to do crops and stuff. ;)
Maybe other users felt the same way.

I find it hard to believe that the fresnel would cause that much of a focus shift (25% of the camera to subject distance), especially since we are talking about what should be less than a 1mm change in the lens to focus plane distance.

Anyway, I will shut up now and await the results Jeremy's tests.

Bob

kev curry
2-Dec-2009, 12:16
Small screw driver in hand I done a bit of quick 'dry' testing today to try and understand if my Chamonix had any problems. I tested to see if the position of focus changed in relation to the camera bed or in my case the focusing scale on the focusing wheel with the gg/fresnel in three different configuation...

(Omega 3.6x loupe)

1.fresnel nearest the lens with gg on top. As sold by Cham...

2. gg only no fresnel.

3. gg nearest the lens fresnel on top.

I tested 5 lenses. SWD 75mm/5.6. SA 90mm/f8. Apo Symmar 210mm/5.6. Commercial Ektar 8/1/2''/f6.3. Nikkor M/300mm Tested at about 2m, 15m and infinity.

The 75/90/8 1/2'' showed significantly different positions of focus between configurations 1 and 2 and most pronounced at 15m. No change at configuration 3.

The 210 and 300mm showed up slight differences between configuration 1 and 2 but far less than the other 3 lenses. No change at configuration 3.


I made a very fuzzy neg a few months ago with the Ektar and couldnt understand why. I just put it down to being careless...now I know what happened.

I also discovered I could easily live without a fresnel too!

Mike1234
2-Dec-2009, 12:18
Yes, let's all just enjoy the silence until real-world testing is available. Everyone breathe now... j-u-s-t -- b-r-e-a-t-h-e. :)

Clement Apffel
2-Dec-2009, 12:25
I find it hard to believe that the fresnel would cause that much of a focus shift (25% of the camera to subject distance), especially since we are talking about what should be less than a 1mm change in the lens to focus plane distance.

Anyway, I will shut up now and await the results Jeremy's tests.

Bob

you make a point.
as it was on "real" shots, the focus shift distance was only appreciated on the ground before the subjects.
so I guess there is no way to actually measure the distance.
But the point is it was before the subject.

maybe not a meter. but 50cm ? 30cm ? couldn't say.

Though, the error was systematically enough to put the focusing error aside.

waiting jeremy's tests as well

shadowleaves
2-Dec-2009, 12:34
Yes, let's all just enjoy the silence until real-world testing is available. Everyone breathe now... j-u-s-t -- b-r-e-a-t-h-e. :)

The real-world test - I did it long time ago. Just go back this thread and find my post with an attached pic, using a fresnel with a hole drilled in the center. It was shocking to see that obvious difference in focus position with and without the fresnel, but it's good to know, after all. According to Chamonix's annoucement, the pre-drilled fresnel will be standard on every new 045n1 made by Chamonix. That's a very reasonable solution as I see it. What's more to be worried about on this matter?

Michael Rosenberg
2-Dec-2009, 12:41
I had posted this information a few months ago:

Quote:
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
I was a little baffled with this thread. Two people with the same camera having identical problems with a particular focal length lens. I would have thought that the Chamonix being a new camera the position of the gg/fresnel combination would have been tested. So I thought I would test my own Chamonix, and using mm ruler verify any small differences if they existed.

For a target I used a window mat on a mat board that would provide a bright line (reflecting the overhead light), and a dark line that would be a shadow from the overhead light. Both lines would be parallel to each other, and the target would also test flatness of the gg (i.e. there should be no change in focus of the parallel lines).

I checked three lenses, my 58mm Schneider XL, 90mm Linhof Scneider Angulon f5.6, and my Apo Sirornar S 135mm. All were tested with either the fresnel in the proper position, with it on top of gg, and no fresnel - just the Chamonix gg. I used a Scneider 6X loupe to check for focus.

With the 58mm lens the focal shift +0.5 mm with the fresnel in the proper place. With the 135mm lens the focal shift was +1 mm with the fresnel in the proper place. This should not make a big difference in depth of field unless shooting wide open I would think. However, with the 90mm lens the focal shift was +3.5mm with the fresnel in the proper place. There was no focal shift when the fresnel was placed on top of the gg. I have tried 2 other gg that I have, and made the same observation.

One possible explanation is the focal length of the fresnel is affecting the focus of 90mm lenses. I do not have another fresnel to test. But I think hereafter I will keep my fresnel on top.
End Quote:

I also followed up that I had put a Maxwell screen from another camera (that I had sold) on the Chamonix and saw no focus shift. I had a thicker cover glass so I cut shims (hose washers) for the gg hold-downs.

I honestly cannot see in any of my images that there is a focusing issue, but I generally stop down f22 or greater. I have had my camera almost two years. I think the only way this issue affects me is maybe where dof was critical and objects closest to me weren't as sharp as I may have thought - but that maybe operator error.

Mike

Clement Apffel
2-Dec-2009, 12:58
I find it hard to believe that the fresnel would cause that much of a focus shift (25% of the camera to subject distance), especially since we are talking about what should be less than a 1mm change in the lens to focus plane distance.

Anyway, I will shut up now and await the results Jeremy's tests.

Bob

I just did some basic optical calculations and here are the numbers :

with a 150mm lens. when focused on a 5m away subject, a 1mm focus shift towards the user means a 86cm focus shift in the "object space"
and a 0.5 focus shift is a 47cm shift.

4m away subject, 1mm focus shift is a 56cm shift
and 0.5mm focus shift is a 30cm shift.

Mike1234
2-Dec-2009, 12:59
That's certainly enough to make a difference....

mortensen
2-Dec-2009, 14:58
After reading this thread and many others it seems that many believe fresnel lenses are actually unnecessary elements that are counter-productive to accurate focusing and often inhibit more than they help. Or am I missing something? So why are they so common if they suck? After reading many posts I get the strong feeling that the fresnel SHOULD be mounted to the outside (viewer side) of the GG and that we should keep an array of different FL fresnels to accomodate specific FL ranges of lenses and the appropriate fresnel should only TEMPORARILY be placed on the GG as needed to compose/focus. Does this sound right to those in the know?

I second that question!!! It would be really nice to hear some opinions from the experienced folk around here. Or is it a topic for a new thread, Mike?

I've taken my fresnel out on the 'right' side of the GG of my 45n-1, but still haven't found any mechanism that gives me the ability to put it on, when demanded only (I'm not going for the paperclip trick, though it probably works fine). Haven't tried shooting without the fresnel yet - we only have around six hours of daylight in DK currently... and those are working hours.

Sal Santamaura
2-Dec-2009, 15:30
...It would be really nice to hear some opinions from the experienced folk around here. Or is it a topic for a new thread...?...No, it's a topic for a multitude of old threads.

I can only speak for myself, but suspect that other experienced folk around here also tire of the forum being used as a chat room rather than the rich resource it is. Perform a Google advanced search under the domain largeformatphotography.info and you'll find a wealth of answers to these repeated questions.

mortensen
2-Dec-2009, 15:41
thanks. will do search. point taken

(that being said, I often spend a lot of time searching in here, not finding excactly what I'm looking for... and isn't it part of the fun of being experienced, that all of us newbies take you so darn seriously and follow every step of advice we are given? or am I completely missing the point? sorry for chatting...)

BradS
2-Dec-2009, 15:51
...but, but, but.....this is a chat room :confused:

Sal Santamaura
2-Dec-2009, 17:52
...but, but, but.....this is a chat room...Not intentionally.

Steve Hamley
2-Dec-2009, 18:18
So what's the depth of the image-forming sensor (plane of focus) in the Betterlight? Wouldn't you have to know this to interpret the applicability to film in film holders?

Cheers, Steve

Jeremy Moore
2-Dec-2009, 18:21
So what's the depth of the image-forming sensor (plane of focus) in the Betterlight? Wouldn't you have to know this to interpret the applicability to film in film holders?

Cheers, Steve

It's made to be a direct slide-in replacement for a 4x5 film holder. Think much like the Sinar or Calumet roll film holders that just slide in under the ground glass.

Marko
2-Dec-2009, 19:20
...but, but, but.....this is a chat room :confused:


Not intentionally.

It depends on whose intention we are talking about.

But no, this isn't a chat room. This is actually a discussion board. They were invented so that physically remote individuals or groups could discuss their common interests. Chatter can and often is a part of any discussion. The only real difference is that chat room communications are happening real-time and discussion boards provide time shift.

IOW, the distinction is largely technical and neither is intended to be an academic repository. There's no reason why people shouldn't simply chat back and forth if they so desire.

David Karp
2-Dec-2009, 20:10
As I read through this, I can't help but wonder if the responses would be different if this camera was from Wisner and he came up with a similar solution.

rugenius
2-Dec-2009, 20:17
Must be a hell of a lotta people interested or using the Chamonix 045N to get all of this attention?

I'll agree to disagree with the shortcomings....
Mine is working fine so far.
Keep the feedback going!

Bill:)

Mike1234
3-Dec-2009, 00:12
...I second that question!!! It would be really nice to hear some opinions from the experienced folk around here. Or is it a topic for a new thread...


No, it's a topic for a multitude of old threads.

I can only speak for myself, but suspect that other experienced folk around here also tire of the forum being used as a chat room rather than the rich resource it is. Perform a Google advanced search under the domain largeformatphotography.info and you'll find a wealth of answers to these repeated questions.

Sal, search engines are great but sometimes the subject matter is far too esoteric to find very specific answers to. If my and mortensen's question(s) were regarding how to change a flat tire then your point would be more appropriate. No offense intended but, in this case it just comes off as disdain towards those without your knowledge. Why not just answer the question since you already have that expertise?

Sal Santamaura
3-Dec-2009, 08:56
Not intentionally.


It depends on whose intention we are talking about...

I refer to Philip Greenspun's intention. This forum originated on LUSENET. The matter of how a forum gets used is not always easy to obtain consensus on. Philip was quite clear that he intended LUSENET to be an archival resource, not a chat room. I agree with his approach.

See this

http://www.ombwatch.org/node/266

for more information; scroll around 3/4 down to find his ARS Digita references.


Sal, search engines are great but sometimes the subject matter is far too esoteric to find very specific answers to...No offense intended but, in this case it just comes off as disdain towards those without your knowledge. Why not just answer the question since you already have that expertise?You are misinterpreting my post. It was not motivated by disdain toward those without knowledge. Rather, I'm weary of those unwilling to search. The subject being discussed in this thread is not esoteric for this forum. It has been covered in detail many times before. The answers exist for those interested enough to find them rather than cluttering the archive with repetition (which makes future searches more difficult).

Jeffrey Sipress
3-Dec-2009, 10:14
If the fresnel that Chamonix provides is causing all these problems, how is putting a hole in the center going to fix it?

Marko
3-Dec-2009, 10:30
I refer to Philip Greenspun's intention. This forum originated on LUSENET. The matter of how a forum gets used is not always easy to obtain consensus on. Philip was quite clear that he intended LUSENET to be an archival resource, not a chat room. I agree with his approach.

I am not sure how relevant Greenspun's original intention might be after all this time and all the changes that happened since then.


See this

http://www.ombwatch.org/node/266


I know about this source. The very first two paragraphs spell it all out:


Websites are great for presenting information to wide geographically dispersed audiences. Frequently, however, site visitors like to contribute their thoughts regarding not only the design or general content of a site, but specific perspectives on the information a nonprofit site shares with them.

For this reason, a number of websites feature an online bulletin or message board (also called a comment area, discussion, forum, or conference). This is different from a chat room in that it is not a space for real-time interactive discussions, but is simply a central spot for electronic messages to be posted, such that messages can be posted, and related postings can be threaded together.

I added bold for emphasis. If there is a way to make this any clearer, I would like to know it.

Larry Gebhardt
3-Dec-2009, 11:08
If the fresnel that Chamonix provides is causing all these problems, how is putting a hole in the center going to fix it?

I imagine the intent is to let you focus through this hole, and compose using the rest of the fresnel. It seems like a terrible solution to me. Sort of like using and autofocus camera with only one sensor. Put it on a tripod and careful composition becomes impossible.

While I didn't buy the camera for the fresnel, I have discovered I really like having one for wide angle composition. While I have not had any noticeable issues, it seems it is only a matter of time that I don't stop down enough to hide the problem. I moved my fresnel to the back with a mylar cover sheet. I'll replace the mylar with a sheet of 1/16th inch glass, once I find some. If that turns out not to work I'll get a Maxwell screen.

mortensen
3-Dec-2009, 11:46
I moved my fresnel to the back with a mylar cover sheet. I'll replace the mylar with a sheet of 1/16th inch glass, once I find some. If that turns out not to work I'll get a Maxwell screen.

Could one ask you to post an image of that solution? I just took my fresnel off the camera... and with my 8x loupe it seemed to be a sharper (and darker of course) image on the GG... but for composition it would still be nice to be able to use the fresnel from time to time.

Larry Gebhardt
3-Dec-2009, 11:51
Right now I just have the fresnel set against the ground glass, and a thin sheet of mylar over that. It's currently just taped in place until I can verify I like the way it works. Once I'm sure I like it I'll build some clips to hold it all together. As of now it's too embarrassingly ugly to post a picture of.

mortensen
3-Dec-2009, 11:54
Haha :)
following the advice from Sal, check this tiny thread about the fresnels in general: http://www.largeformatphotography.info/forum/showthread.php?t=1714

(now that is showing good manners, isn't it?)

Clement Apffel
3-Dec-2009, 13:19
Just my 2 cents :

I agree with you, mortensen on image to be sharper and easier to focus without the fresnel (any fresnel, not just chamonix's).
That is why I insta-removed it when I figured out it was causing the focus shift (Jeremy's test will tell us more about that though.)

Though, I use 90 and 65mm lenses and composing through GG without fresnel is not a very viable solution indeed.
But actually I never liked composing on ground glass anyway, I always used a wooden 4x5 frame with a thin cord with markings allowing me to simulate the angle of view of all 3 lenses I have.

On the field, I always start by pulling the wooden frame out of the bag. I compose, find the point of view and frame. and THEN I put my bag on the ground and set the camera up. knowing it will be exactly at the perfect spot.

This way, I am not composing on the GG, just checking some reference points I mentaly noted to be in the lower left corner, and another in the upper right corner for example.

that is why I quickly took the decision to remove the fresnel as it was kinda useless to me anyway.
and was interfering with my focusing.

just another users feedback.

regards,
CA

mortensen
3-Dec-2009, 14:09
nice one, Clement... it's one of the old Ansel Adams methods, right?

thanks for sharing.

and on a chat-tip, I just read about the satin snow GG's... but the web is down, it seems. Might be an interesting option for a maybe-soon-to-be-fresnelless-shooter?

Clement Apffel
3-Dec-2009, 15:06
it's one of the old Ansel Adams methods, right?

I don't know :)

I actually found out that one alone quite some time ago.
Just because I didn't felt confortable moving the camera around while composing. it felt a bit too disorganised and random to me.
I guess some other more experienced folks can just mentaly do that frame without it, knowing their lenses' angle by heart.
But that's over my head for now.

Jeremy Moore
3-Dec-2009, 15:23
and on a chat-tip, I just read about the satin snow GG's... but the web is down, it seems. Might be an interesting option for a maybe-soon-to-be-fresnelless-shooter?

The business has been shuttered by the owner. They did make a great GG.

Steve Hamley
3-Dec-2009, 17:57
Try Steve Hopf's groundglass; he does business on eBay as "photofixation".

Cheers, Steve

Bruce Barlow
4-Dec-2009, 05:55
Wow. Just read all this.

Makes me thankful for Richard Ritter. He figured out a stiffer baseplate for his 8x10, and offered to replace everybody's for free, as I recall. The camera was fine (I love Alice, my Ritter 8x10, and had no problem with stability), it was just better with a stiffer plate. Pretty cool, IMHO.

Alice is being rehabbed right now, and from time-to-time I visit her in the camera hospital. I'm patient while Richard's backed up with paying work, and I think Alice is going through a fuill-camera transplant from her prototype status to improved production model, which requires waiting for new bellows to arrive. We'll probably use the original Alice as a workshop camera. Visits are a good excuse to have breakfast with Richard at the Dam Diner (behind the Townshend Dam...yuk yuk, get it?), but that's always a treat.

Richard wouldn't create the "problem" in the first place, and if he did, you can bet he's fix it for free.

Mike1234
4-Dec-2009, 07:52
Wow. Just read all this.

Makes me thankful for Richard Ritter. He figured out a stiffer baseplate for his 8x10, and offered to replace everybody's for free, as I recall.

That's the difference between good/fair business tactics and less than perfect business tactics. Of course, there is that big price difference thingy that always seems to throw a wrench in the works. I sure wish I could afford a Ritter though!!

Jeremy Moore
4-Dec-2009, 09:13
Richard wouldn't create the "problem" in the first place, and if he did, you can bet he's fix it for free.

Richard doesn't have a 4x5 camera listed on his website. I paid under $650 for my Chamonix 4x5 whereas Richard's cheapest camera (an 8x10) is nearly $3,000--more $$$ than I have in my entire 4x5 system.

I don't see how this adds anything to this discussion other than a fanboy shout-out to Ritter. Then again, my camera isn't in rehab and I've been shooting with it every day.

Jeremy Moore
4-Dec-2009, 09:17
That's the difference between good/fair business tactics and less than perfect business tactics. Of course, there is that big price difference thingy that always seems to throw a wrench in the works. I sure wish I could afford a Ritter though!!

What "less than perfect business tactics"?

Chamonix has decided to fix the problem at the factory level by drilling a hole in the fresnel. Regardless of whether you agree with the fix, they are doing this for free for anyone who wants it done on their 45N-1--just return the camera to your dealer.

Mike1234
4-Dec-2009, 10:39
While I'm sure everyone appreciates Chamonix' offer to drill a hole in their fresnels, IMHO, it's a "less than perfect" solution because it doesn't solve the actual flaw which is the basis of this arguement, after all. No matter how one looks at it, they messed up and all those cameras they sold will always have that flaw unless they replace the focus panel using their own funds or accept the limitations of having a hole in their fresnel. Drilling holes in the fresnel is a band-aid... not a cure.

That said, this thread among others has convinced me that no in-front fresnel will suit my needs. I'll buy an acid etched focus panel and have at least 3 fine quality fresnels of different FL's for use behind the focus panel that are easily/quickly installed and removed. For this knowledge I'm humbly grateful.

Bob Salomon
4-Dec-2009, 11:21
That said, this thread among others has convinced me that no in-front fresnel will suit my needs. I'll buy an acid etched focus panel and have at least 3 fine quality fresnels of different FL's for use behind the focus panel that are easily/quickly installed and removed. For this knowledge I'm humbly grateful.

As the Linhof and Wista Product Manager (Linhof for 30 years next month) You are going greatly overboard. You should not need a bunch of fresnels. The gg and fresnel supplied by major camera manufacturers is usually a combination that will work effectively with the widest range of focal lengths that would commonly be used on the camera. In the case of Linhof I can't think of one instance that the problems detailed in this thread have happened.
Old Linhofs placed the Fresnel under the ground glass, and adjusted the gg shims accordingly. When Fresnel screens became less likely to scratch by looking at them (early field lenses were very delicate) Linhof moved the Fresnel to the back side of the gg so it can be easily removed or replaced by the shooter. Sinar does exactly the same thing on their cameras.

Adding or removing a properly installed Fresnel should have no effect on the focusing of an image, except to make it easier by evening out the illumination across the gg. The lines on a Fresnel are normally not a problem providing that the focusing loupe has been focused correctly on the grain of the gg and not just laid on top of the gg or the gg/Fresnel.

Yes there are companies that make Fresnel screens of different focal lengths for different lenses, Wista is one of those companies. They make a long focal length Fresnel. No one in over 30 years has ever approached us for a Fresnel specifically for very short lenses for Linhof, Sinar or Wista. And we rarely get calls for that long focal length Wista Fresnel.

If a Fresnel, under a gg is causing incorrect focus then the gg position is incorrect. Simply placing the Fresnel on top of the gg or throwing the Fresnel away will not be an automatic cure as someone earlier noted, the thickness of the Fresnel has an effect on focus as any piece of glass or plastic in the optical path shifts the focus by about 1/3rd the thickness of whatever is placed there.

The first thing that you want to check is the focus on and inclined yard stick, with the Fresnel and gg in the factory position. Put a vertical flag pin on the yardstick at the point you are focusing on and focus with a loupe of 4 to 6x power whose eyepiece is adjusted to bring the grain of the gg into sharp focus. Focus on the point where the flag pin is inserted into the ruler. Make an exposure wide open and at f22. Make sure that the lens is within the optimization range for the magnification you are using. Testing with a lens corrected for 1:20 at this range won't tell you much as the lens will not perform optimally.
What is the result? The focus spread on either side of the flag pin will tell you what is happening. Focusing on a flat target will not.

Then try it without the fresnel. What happens? Can the gg be shimmed forward or back? Should be able to if the camera is properly made. Otherwise what happens if a camera is dropped or banged and goes out or from just wear or loose springs?

Reposition the gg and retest until you get the correct gg position. Then put a good Fresnel on top of the gg.

Good luck

Jeremy Moore
4-Dec-2009, 11:32
If a Fresnel, under a gg is causing incorrect focus then the gg position is incorrect. Simply placing the Fresnel on top of the gg or throwing the Fresnel away will not be an automatic cure as someone earlier noted, the thickness of the Fresnel has an effect on focus as any piece of glass or plastic in the optical path shifts the focus by about 1/3rd the thickness of whatever is placed there.

The problem was originally stated to me as the factory correctly installed and placed the GG (for no fresnel) and THEN added the fresnel.

Mike1234
4-Dec-2009, 11:38
Bob, so I should be able to find a fresnel/GG combo that works really well without the focus shifts nor any funky corner issues for lenses that range from 38mm to 450mm? Which ones should I look for? BTW, I won't be focusing through the fresnel... just getting my compositional bearings.

David Karp
4-Dec-2009, 11:59
Mike,

It seems like one Fresnel will be enough for you if you are not going to focus through it. If you compose with the Fresnel and then focus finely using the GG, you have nothing to worry about.

Jeremy Moore
4-Dec-2009, 12:00
Bob, so I should be able to find a fresnel/GG combo that works really well without the focus shifts nor any funky corner issues for lenses that range from 38mm to 450mm? Which ones should I look for? BTW, I won't be focusing through the fresnel... just getting my compositional bearings.

Mike, for my own edification, do you regularly shoot with 38mm - 450mm lenses on one camera?

Mike1234
4-Dec-2009, 12:22
Mike, for my own edification, do you regularly shoot with 38mm - 450mm lenses on one camera?

Jeremy,

I plan to, yes. When I shot 4x5 years ago I used 65, 90, 150, 210, and 300mm lenses and there were times I wished I had a wider or longer lens. BTW, I'll only be shooting 6x12cm with the 4x5in camera and the lenses are 38, 58, 90, 135, 200, 300. I don't know whether I'll ever shoot with a 450 on 6x12cm but I have it for the 5x12in kit anyway so I may as well take it along for the ride. I'm sure the 58 through 200 will see the most use.

Mike1234
4-Dec-2009, 12:28
Mike,

It seems like one Fresnel will be enough for you if you are not going to focus through it. If you compose with the Fresnel and then focus finely using the GG, you have nothing to worry about.

David,

You're saying I won't have to worry about those funky corner issuse with a mismatched fresnel where the corners are masked with rings? Those really bug me because I can't see the image to compose.

Peter K
4-Dec-2009, 12:31
Bob, so I should be able to find a fresnel/GG combo that works really well without the focus shifts nor any funky corner issues for lenses that range from 38mm to 450mm? Which ones should I look for? BTW, I won't be focusing through the fresnel... just getting my compositional bearings.
Short focal fresnel-lenses behind the gg will work also with longer taking lenses - I don't know up to 450mm-lenses - but long focal fresnel-lenses won't work well with short taking lenses.

Mike1234
4-Dec-2009, 12:35
Short focal fresnel-lenses behind the gg will work also with longer taking lenses - I don't know up to 450mm-lenses - but long focal fresnel-lenses won't work well with short taking lenses.

So the key is to find a fresnel matched to the 38mm used behind the focus panel... and all is well all the way through 300mm? BTW, I not convinced a fresnel is really needed for 200mm and longer for 6x12cm or 4x5in anyway.

Jeremy Moore
4-Dec-2009, 12:36
Jeremy,

I plan to, yes. When I shot 4x5 years ago I used 65, 90, 150, 210, and 300mm lenses and there were times I wished I had a wider or longer lens. BTW, I'll only be shooting 6x12cm with the 4x5in camera and the lenses are 38, 58, 90, 135, 200, 300. I don't know whether I'll ever shoot with a 450 on 6x12cm but I have it for the 5x12in kit anyway so I may as well take it along for the ride. I'm sure the 58 through 200 will see the most use.

Makes sense. I only shoot with 2-3 and 90% of my work is with 1 so I was just curious.

Bob Salomon
4-Dec-2009, 12:37
Bob, so I should be able to find a fresnel/GG combo that works really well without the focus shifts nor any funky corner issues for lenses that range from 38mm to 450mm? Which ones should I look for? BTW, I won't be focusing through the fresnel... just getting my compositional bearings.

We have had no complaints with 35mm up with the Linhof Fresnel. I have no idea if it will fit your camera. You should also have no problem with a Sinar Fresnel. We have also not had any reported problems with a Wista Fresnel.

Bear in mind that cameras function differently. Linhof cameras have either an optical axis front tilt or an asymmetrical axis front tilt. Many folding cameras have a base tilt on the front. With an optical axis tilt there is no, or very little shift of the image placement on the gg. With a base tilt camera there can be a great amount of image displacement - depending on the amount of movement. When you use a loupe and an enhancing means it will be necessary for your eye to remain in the optical path to maintain optimal screen brightness. This can become tricky especially with very wide lenses. It usually means that the loupe ends up tilted and displaced, especially with a base tilt camera. That is one reason why on Linhof's asymmetrical axis M679 system cameras the Fresnel is cut off center and has a handle on it so it can slide to keep the optical center of the Fresnel in the optical center of the lens as tilts are made. If this was not done you could black the entire image out. Guess 121 years of camera manufacturing experience can solve vexing problems.

Mike1234
4-Dec-2009, 12:52
Bob, okay I'll study a bit more and look into the brands you mentioned.

Peter K
4-Dec-2009, 12:52
BTW, I not convinced a fresnel is really needed for 200mm and longer for 6x12cm or 4x5in anyway.
That's true if one uses no focusing-mirror or a focusing and measuring bellows.

Mike1234
4-Dec-2009, 12:58
That's true if one uses no focusing-mirror or a focusing and measuring bellows.

By "focusing mirror" you mean a reflex hood? Maybe not but I'm not ruling one out. There is a problem with these when used with a mismatched fresnel because it fixes the eye in one spot making one unable to move his head around to see the image, right? By "focusing and measuring bellows" you mean a monocular hood? I might want one of these but they have the same problems as the "focusing mirror"?

kev curry
4-Dec-2009, 13:20
Last night I set up my Tachihara, (my 1st 4x5) and to my surprise the fresnel was sitting where its always sat...on top of the gg nearest the viewer! Ive never questioned or to be perfectly frank ever even thought about it before, I'm still a greenhorn see... all I ever did was marvel at how fabulously bright and easy it was to compose and focus on that screen. I never worried about scratching the fresnel, it never occurred to me that there even existed the potential to scratch it, and its never happened anyway.
I then set up my Tech V (this was a great present from a dear friend:) ) and got another surprise! The Tech's configured in the same way i.e the fresnel is sitting on top of the gg!

This put this whole issue into its proper perspective (for me)

According to the manufacturer the chamonix was designed and built without a fresnel in mind and the fresnel was added latter due to customer demand.

Anyway Ive got the fresnel on top of my Chamonix's gg, whats the problem?

Bob Salomon
4-Dec-2009, 13:21
By "focusing mirror" you mean a reflex hood? Maybe not but I'm not ruling one out. There is a problem with these when used with a mismatched fresnel because it fixes the eye in one spot making one unable to move his head around to see the image, right? By "focusing and measuring bellows" you mean a monocular hood? I might want one of these but they have the same problems as the "focusing mirror"?

Linhof makes two viewing accessory devices that require a fresnel. The first is the Right Angle Reflex Accessory. It has a very large diameter eyepiece and you can easily move your eye around but as it is about 2x magnification it allows you to see the entire gg at one time. Like all Linhof viewing accessories it is hinged and will swing down if you want to get a high power loupe on the gg for critical focusing. You can also take the right angle part off by swinging a lever which turns the base part into a hood for the gg.
The second accessory is the Focus/Metering Bellows which also attaches the same way as the Right Angle Reflex Attachment. The Bellows has two 2x magnifiers in
the eyepiece. Use both together for 4x magnification. You can position the eyepiece any place on the gg. Even in the edges and corners. Unscrew the top 2x loupe and you can pull the eyepiece back so you can view the entire gg at 2x magnification.
The third viewing accessory from Linhof is a standard part of a Technika but an accessory on all of their other 23 and 45 cameras. It is the Folding Focusing Hood. This can be added as an accessory to any Linhof 23 or 45 camera and has no focusing aid or loupe in it. It is simply a folding hood.
Linhof only makes a monocular hood. A long time ago they made an adapter for the Sinar Binocular Hood but it ended up being a very clumsy system. The monocular system proved more convenient. Especially since you are viewing a two dimensional glass screen and use your dominant eye to compose anyway at that distance.

Bob Salomon
4-Dec-2009, 13:23
According to the manufacturer the chamonix was designed and built without a fresnel in mind and the fresnel was added latter due to customer demand.

Anyway Ive got the fresnel on top of my Chamonix's gg, whats the problem?

Nothing, unless the grain side of the gg changes position when that factory installed Fresnel is removed. Or if the factory changed the grain side position to compensate for the focus shift when the Fresnel is under the gg.

Jeremy Moore
4-Dec-2009, 13:41
Nothing, unless the grain side of the gg changes position when that factory installed Fresnel is removed.

There is no shift in GG position as the fresnel is recessed on a plane closer to the lens than where the GG sits. Remove the fresnel doesn't change the plane the GG is on.


Or if the factory changed the grain side position to compensate for the focus shift when the Fresnel is under the gg.

That's what I'm wondering now as I the first story I heard here is that the cameras are constructed w/ the GG at the correct placement then they add the fresnel. The new .pdf on their website seems to state that this is not true, though, and the GG position is based on the fresnel being installed.

Bruce Barlow
4-Dec-2009, 15:10
Richard doesn't have a 4x5 camera listed on his website. I paid under $650 for my Chamonix 4x5 whereas Richard's cheapest camera (an 8x10) is nearly $3,000--more $$$ than I have in my entire 4x5 system.

I don't see how this adds anything to this discussion other than a fanboy shout-out to Ritter. Then again, my camera isn't in rehab and I've been shooting with it every day.

Wow. What a grump. At least try to read and get it right.

I'm pretty sure I never said that Richard had a 4x5. I was reading a thread about a company that admits a design flaw and won't fix it. I have a friend whose business practices are better than that. In this day and age, that's worth celebrating.

For those who have the money, Richard's camera is an excellent choice. But, Mr. Moore, what Richard's camera costs is your irrelevant contribution, other than to allow me to note that he makes them himself, and charges a fair wage for his time embedded in the camera's cost. Yup, $650 is a lot less than $3,000, but 8x10 is a lot bigger than 4x5, and whether there actually is a problem with the Chinese camera, the mere controversy in this thread is enough to make me run away, whereas Richard has a long history of standing behind what he makes. My Wista serves me just fine: its fresnel is behind the GG. Richard tells me he likes the Chamonix. Especially certain parts.

And yup, you're welcome to call it a fanboy shoutout. Cuz it is, because he far more richly deserves it than many.

Alice is in rehab because she was the first ever built - readers could see that I called her a "prototype." I was the guinea pig to check out how she worked. Some of her aluminum parts aren't black anodized, she has no levels, and there are a few extra holes in her back box. She worked flawlessly for me. But that wasn't good enough for Richard.

Now here's another fanboy shoutout: careful readers would have read that Richard is giving me an entirely new camera to replace the original Alice, one that is fully a production unit. How many manufacturers would do THAT? Careful readers would know that we're waiting for bellows to arrive, and that I don't mind the wait because the breakfasts are tasty and fun, and, as I wrote, I want Richard to do the paying work first, such as the 20x24 he has finished that has 90 inches of bellows extension. We're going to make a special video owners manual just for it, one copy. And yes, Mr. Moore, it's a hair more expensive than $3,000. I'm not out of business, I still have Norma for 8x10, 5x7 and 4x5. And the Wista when I want to use little film. So you can try to fabricate criticism of Richard, but waiting is my choice.

And just so you know, I paid full price for Alice, less a discount that Richard gave me unasked. He's a friend, but he also pays for groceries, and I try not to take advantage of the friendship. And I usually pick up the breakfast check, too. So I'm not a paid fanboy shouter. I do it for the worthy for free.

Darin Boville
4-Dec-2009, 15:15
Oh my.

--Darin

kev curry
4-Dec-2009, 15:47
Oh jings.

Marko
4-Dec-2009, 16:07
Good thing that politics and religion are banned, how else could we distinguish The Lounge from the main area? :D

Jeffrey Sipress
5-Dec-2009, 10:32
Back to the 'hole'. If the fresnel is causing focusing issues in the corners of the image, how is a hole in the center going to fix anything?

And, today when I disassembled the glass & fresnel to get a closer look, I noticed that the recess in the wood to accommodate the fresnel is a bit shallower (estimate .010 to .015") than the thickness of the fresnel, therefore causing the GG to rest on the fresnel rather than on the wood, when the black hold downs are snugged up. Removing the fresnel would then cause the GG to be in a different position relative to the camera back. How am I to know if Chamonix designed it that way?

dsim
5-Dec-2009, 10:47
In spite of the tug of war, I sure I'm not alone in saying that I learnt a lot from this thread. Thanks to everyone for their contribution.

Peter K
5-Dec-2009, 11:33
Back to the 'hole'. If the fresnel is causing focusing issues in the corners of the image, how is a hole in the center going to fix anything?
If you're focusing through the hole and you don't load a fresnel lens on top of the film in the filmholder you should get a sharp image. But only if the back of the camera, gg position and position of the inserted filmholder, at least meet the specifications (http://home.earthlink.net/~eahoo/page8/filmhold.html) for filmholders.

Mike1234
5-Dec-2009, 12:06
If one focuses through this center hole... how does he focus the corners?

Peter K
5-Dec-2009, 13:23
If one focuses through this center hole... how does he focus the corners?
That's a good question ;)

For technical work like reproductions etc. I'm using a gg with a clear spot in the center. Also the Zeiss "Ultraphot", a photomicroscope, has clear stripes in a "X"-pattern to focus with a loupe up to the corners on the gg. One can train the eyes to "ignore" the clear aereas like the clipped corners in certain ground-glasses but this won't help with a wrongly mounted fresnel-lens.

In any case for portraits, landscapes etc. I prefer a plain gg or one with a light grid. But this needs an easily exchangeable gg-holder without losing the precision of the camera.

GPS
5-Dec-2009, 15:09
If one focuses through this center hole... how does he focus the corners?
The short answer is - you cannot focus correctly in the corners with the wrongly put Fresnel screen - regardless of the fact that it has or not a central hole.
But! - give an innovative idea to Chamonix... how about a Fresnel screen with a hole in the center AND a hole in each corner! ;) If it works in the center it would work in the corners too. :)

Peter K
5-Dec-2009, 15:44
The short answer is - you cannot focus correctly in the corners with the wrongly put Fresnel screen - regardless of the fact that it has or not a central hole.
If one can focus correctly through a hole in the center or elsewhere in the fesnel-lens the course surface of the gg must have the same position as the film-surface when a filmholder is inserted in the camera.

But as one can read here (http://www.chamonixviewcamera.com/Fresnel_lens_problem_of_45N.pdf) - "... all cameras are tested for the accuracy of the Fresnel position before leaving our factory..." - it looks like the position of the gg plus fresnel-lens is aligned with a certain lens of a certain focal-lenght in the factory. So if one removes the fresnel-lens or replaces it with a fresnel-lens with a hole the position of the gg has to re-aligned too.

So this looks like Chamonix corrects one fault with another one.

Peter

GPS
5-Dec-2009, 16:13
If one can focus correctly through a hole in the center or elsewhere in the fesnel-lens the course surface of the gg must have the same position as the film-surface when a filmholder is inserted in the camera.

But as one can read here (http://www.chamonixviewcamera.com/Fresnel_lens_problem_of_45N.pdf) - "... all cameras are tested for the accuracy of the Fresnel position before leaving our factory..." - it looks like the position of the gg plus fresnel-lens is aligned with a certain lens of a certain focal-lenght in the factory. So if one removes the fresnel-lens or replaces it with a fresnel-lens with a hole the position of the gg has to re-aligned too.

So this looks like Chamonix corrects one fault with another one.

Peter

Thanks, Peter, (a lot)
finally we start to touch the original question - the nonsensical Chamonix announcement. Why the heck, when Chamonix does not "recommend that users of 45N-1 camera to change the position of the Fresnel lens as all cameras are tested for the accuracy of the Fresnel position before leaving our factory" (a citation with the incorrect English used in it) are the users - in the same announcement - advised to take the Fresnel out completely??? The very same "tested and accurately put Fresnel" in question??
What Chamonix does is "correcting" one fault with a lot of nonsense added... In that I agree with you.

Steve Hamley
5-Dec-2009, 16:26
Back to the 'hole'. If the fresnel is causing focusing issues in the corners of the image, how is a hole in the center going to fix anything?

And, today when I disassembled the glass & fresnel to get a closer look, I noticed that the recess in the wood to accommodate the fresnel is a bit shallower (estimate .010 to .015") than the thickness of the fresnel, therefore causing the GG to rest on the fresnel rather than on the wood, when the black hold downs are snugged up. Removing the fresnel would then cause the GG to be in a different position relative to the camera back. How am I to know if Chamonix designed it that way?

Jeffrey,

The idea is to compose and focus normally, using the hole or not, apply your swings and tilts, then refocus using the hole and whatever's in front of it. Refocusing will move the entire glass the distance of the focus shift, and assumes there won't be more focus shift in the corners which I can't see how there would be if the frsnel is the same thickness and power across the frame.

How would you know if the GG is properly spaced? Well somewhere in this mess or at APUG I posted directions and jpegs, but I'll be darned if I can find them. But it's easy. You need a set of dial calipers and a set of regular external calipers.

First remove the GG and fresnel and use the dial calipers to measure the depth of the GG recess (not the fresnel recess). See jpeg "frame". It should be 0.197 +/- 0.007.

http://home.earthlink.net/~eahoo/page8/filmhold.html

and on our home page here.

If that's what it is, then it's O.K. at least by ANSI specs. Then you'd have to measure the difference between the fresnel thickness and the fresnel recess taking the whatever measurements with the dial calipers on the frame to do that. If removing the fresnel "excess" moves it out of the 0.197 +/- 0.007 range, you have a problem and need to reposition the GG.

You can also measure where the emulsion is relative to the GG. See jpeg "holder". Use the external calipers to record the thickness of the holder, being careful not to get in "grooves", and then the thickness of the septum (shown). To get the calipers off, I had to put a "witness mark" on the turn screw, remove the calipers counting turns, then reposition the caliper back to the original setting. Measure the gap in the external caliper with the internal jaws of the dial caliper. Subtract this number from the holder thickness, divide by two, and you have the septum depth of each of the two sides. Now for Tri-X with a 7 mil base, subtract from the septum depth. For example, if you got 0.200 for a septum depth the emulsion depth would be 0.193, which is within 0.007 of 0.197. Ideally they should be the same, but won't always be because of manufacturing tolerances and film base thickness. Pan-X aerial has a 4 mil base.

If you're running a test, you really should make both measurements, because you won't know if the fresnel has shifted the focus or the emulsion/GG difference, or if that difference is making the fresnel shift worse or better.

Cheers, Steve

Mike1234
5-Dec-2009, 18:06
The more I read on these forums the more I see I don't know what I'm doing nor can I trust all those who post their opinions on them. Big surprise...

eddie
5-Dec-2009, 18:19
steve,

i remove the back and measure to the GG. (with the fresnel removed). then i insert the film holder, pull the slide, and measure to where the film sets.

Steve Hamley
5-Dec-2009, 18:31
steve,

i remove the back and measure to the GG. (with the fresnel removed). then i insert the film holder, pull the slide, and measure to where the film sets.

Eddie,

That should give you the same number (fresnel compensation notwithstanding), and I'd probably do the same if I had a couple of flat pieces of metal and a depth gauge. All I have are calipers.

Cheers, Steve

Steve Hamley
5-Dec-2009, 18:44
The more I read on these forums the more I see I don't know what I'm doing nor can I trust all those who post their opinions on them. Big surprise...

Mike,

Me too, but you can always trust your calipers or depth gauges. All you really want is the emulsion to be in the same place as the GG (sans fresnel lens in front of the GG), and that isn't very hard to measure.

Cheers, Steve

Jeffrey Sipress
5-Dec-2009, 22:57
Eddie & Steve, now we're getting to the truth of the matter. Plenty of chatter, but the measurements are the final word. Being a machinist and engineer (I own the place and we're ISO9000), I can measure accurately to .00005". I can use calipers, depth micrometers, or my Coordinate Measuring Machines ($60K). Fresnel, no fresnel, focusing errors, hole in the middle, whatever anyone wants to talk about, the bottom line is that the sheet of film in the holder must end up on the same plane as the frosty side of the GG. Unfortunately, not everyone has access to these measuring tools or understands their application. Bring your camera back and a holder into a nearby machine shop and have someone perform the inspection.

Game over, man.

Steve Hamley
5-Dec-2009, 23:28
Jeffrey,

Exactly - unless the GG is in the same position as the emulsion then you stick a fresnel in front of it.

I've never understood most of the thread. Chamonix's fix (the hole) is a good one if you want to use the Chamonix-supplied fresnel. If I owned one, I definitely wouldn't want the back re-manufactured so a plain GG would be incorrectly positioned by itself, although if they supplied correct shims for the GG I suppose that would work just as well and would be well within the abilities of most users.

But I'd probably buy an Ebony fresnel and cover glass and be done with it. Or have Maxwell make me one like the Ebony with the frosty side to the lens of course. As someone said earlier, you could do either and still have one heck of a bargain.

Cheers, Steve

Mike1234
6-Dec-2009, 05:33
So, from I've gathered here and from other forums...

1. Have a machine shop test to assure matched depth of frosted side of the focus panel and film (I'll add to test on all four corners as well as center).

2. Use various non-frosted fresnels of appropriate FL for the lens in use at the back (viewing side) of the focus panel and only for composing, not focusing.

3. The finest grind focus panel is best (not a surprise) but acid ethed is even better.

Or am I off base?

GPS
6-Dec-2009, 05:44
Mike1234,
despite of what Jeffrey and Steve say (and at least one of them acknowledges that he doesn't understand the thread), there has never been any problem about the plain gg film registration on this Chamonix camera. You surely can check its distance if you want but it was the handling of the Fresnel that put them in troubles - and the technically unfortunate, incorrect and dishonest explanations afterwards...

Clement Apffel
6-Dec-2009, 05:51
You make a good point on some precise measurement being kind of a thread breaker.
The distances are within tolerance? End of the story.

But…..

I just pulled out the backs of my 2 4x5” cameras.
The Chamonix GG seems to be too close to the lens by something in the 0.2 – 0.25mm range. (that would be 0.08 – 0.09”)
The Cambo GG seems to be too far to the lens by something in the same range.

I do not own any of your measurement tools though. I only was able to make a makeshift measurement.
Actually, it only points out that none of my 4x5” backs is matching GG and film plane.

My point is that I would very likely know if any cameras that all the users here own are within the 0.07” tolerances.
And actually, even a 0.05” error means a 13cm error of the point of exact focus for a 150mm shot focused at 5m.
Or a 40cm (!!!) error with a 90mm lens in those same conditions
Or a 85cm (!!!) error with a 65mm lens again in those conditions.

If you shoot any of those wide open, you’ll be off everytime. Eventhough your back is within the tolerance.
But wait a sec…
What is the depth of field at f/5.6 with those lenses we are talking about ?

Some other basic calculations:
150mm focused at 5m @ f/5.6: 70cm DOP
90mm focused at 5m @ f/5.6: 200cm DOP
65mm focused at 5m @ f/5.6: 431cm DOP
And those calculations are done with an exigent value of the confusion circle.

So my guess is that none of our cameras are at the exact 0 alignment.
Or like 1 out of 100, and by luck. And not on the entire film plane.
I didn’t even mention the film planarity that will never be perfect on all the frame.
What is that error ? 0.03” ? 0.02” ?
A 48 – 31cm error with a 65mm lens focused at 5 meters.

But we don’t care. Cause even wide open the depth of field will cover that error widely.

My Chamonix is off by 0.25mm ? the numbers says it's out of tolerance standards.
But my tests performed under my more exigent condition of uses (i.e. wide open portraits at 4 – 5m distance with a 150mm) were in my (quite demanding) tolerance of sharpness.

So end of the story for me.

Numbers and 0.00....005" precision measurements are probably a good info to have.
But at some point you have to see that this precision is not achieved on any view cameras available today. why ? because we do not need such a precision.

The magic bullet chase again....

regards,
CA

GPS
6-Dec-2009, 06:05
But DOField is different from DOFocus. :)


Exactly!
Now, if everyone knew that.

Just to remind you...:)

Clement Apffel
6-Dec-2009, 06:15
Can you explain that to me more accurately with optics formula and field examples instead of that infertile and snobbish comment? :)
I'm sure you can achieve that.

And please do not ignore the end of my post.

Thank you in advance.

Clement Apffel
6-Dec-2009, 07:12
I just pulled out my dusty optics lessons. Cause the OP seems to be out for a walk, weirdly enough.
So for those like me who don't remember/know what is the difference between DOFocus and DOField, here is a quick definition.
(anyone correct me if I'm wrong, please)


Depth of field is the distance in the object space within which the object point can move and remain sharp while the film being still.


The depth of focus on the other hand is the distance in the image space within which the film can move and stay in the sharpness tolerance while the subject point being still.


Basically we can sum up by saying that DOFocus is the image of the DOField given by the lens.

Now, GPS, can you explain me why this difference makes my previous post irrelevant?
Or maybe I misunderstood your “just to remind you” comment? Was it just a friendly advice to make sure that I knew the words for the things I was talking about?

In that last case I thank you, because indeed I forgot those names and definition.

But my conclusion stays the same.
Thank you again for your comment.

Steve Hamley
6-Dec-2009, 07:27
Clement,

Practically speaking, the DO focus decreases with focal length and the DO field increases. With long lenses the DO focus increases and the DO field decreases. That's why the GG placement is especially important with short lenses and some specialty wide angle cameras have fixed backs.

I have a few high-end cameras that could use some adjustment, so maybe a trip to Richard Ritter this winter. I also traded for a used Ebony SV810U a year or two ago, and the previous owner had a Maxwell screen installed and sent Bill the back. Bill told him the spacing wasn't quite right and had it adjusted. So no, price or brand does not guarantee accuracy. BTW, I did measure my Wehman and it seems spot on except maybe for a burr or two on the wood which could be taken care of fairly easily - but it's very close even so and likely wouldn't be an issue with the longer lenses used for 8x10.

I believe that checking the GG depth is a skill every serious LF photographer should develop, and it's almost essential with the older, non-standard formats.

Sorry for the brief reply, I'm off to take pictures!

Cheers, Steve

Peter K
6-Dec-2009, 08:06
But at some point you have to see that this precision is not achieved on any view cameras available today. why ? because we do not need such a precision.
How do you know this? Or is it only a guess to help to ignore that not all cameras have the precision a LF-camera needs. Possible not needed by you. But if a camera will be used as a tool for taking high-quality images, measuring, photogrammetry etc. and not only for leisure.

BTW the tolerances shown here (http://home.earthlink.net/~eahoo/page8/filmhold.html) are for filmholders. For cameras the tolerances must be much smaller as mentioned by others before too.

And why discuss in e. g. the lens section of this forum resolution-power, MTF-curves of lenses etc. if this lenses will be used with misaglined cameras?

Clement Apffel
6-Dec-2009, 08:35
Just saying that the absolute 0 alignment is not very important for general use.
And that viewcamera factories do not aim this absolute 0 for GG alignment. it is not rocketery science.
Of course if you throw in microphotography or photogrammetry or any other scientific application of photography, you'll need precision accordingly to the exigencies of experience.

But that is not what we are talking about here, sorry.

I'm just saying that measuring the GG alignment with laser is totally overkill for general use.
My standards of sharpness are very demanding for my prints, believe me. And those are fulfilled by both of my misaligned cameras: therefore they are in my standards.
Just sharing this opinion to balance the over-measuring previous posters.

Apply the precision you REALLY need. That’s the bottom line.

I was reacting to some previous poster who started to worry about their GG alignment reading all this thread without having themselves noticed a sharpness issue on their prints.

Regards,

Marko
6-Dec-2009, 09:32
How do you know this? Or is it only a guess to help to ignore that not all cameras have the precision a LF-camera needs. Possible not needed by you. But if a camera will be used as a tool for taking high-quality images, measuring, photogrammetry etc. and not only for leisure.

BTW the tolerances shown here (http://home.earthlink.net/~eahoo/page8/filmhold.html) are for filmholders. For cameras the tolerances must be much smaller as mentioned by others before too.

And why discuss in e. g. the lens section of this forum resolution-power, MTF-curves of lenses etc. if this lenses will be used with misaglined cameras?

Peter, I don't want to sound argumentative, but I don't think any wood field camera could ever be used as a tool for taking the type of high precision images you are mentioning. And we are not even talking about the likes of Ebony but a cheap(er) wood field camera here.

While you are certainly right in the technical sense, most of these cameras will have bigger slop in the movements than the precision required for the back. I think that's what Clement is trying to say and I think that he also has it right in practice and within the scope of this discussion.

On a general note, I will agree with some other posters - this has been a great thread for learning. I will particularly remember it whenever someone mentions pixel-peeping. ;)

Peter K
6-Dec-2009, 12:41
And that viewcamera factories do not aim this absolute 0 for GG alignment. it is not rocketery science.
Again, how do you know? Of course that the maker of the camera in question doesn't care about could be the impression if one reads not only this thread.

Apply the precision you REALLY need. That’s the bottom line.
But what happens if the standards are not parellel if wanted, the gg is misaligned, the filmholder takes not the position of the gg-holder and the film itself lacks of flatness? You will always get unsharp pictures because after Murphy's law, tolerances will always cast up in the wrong direction.

Peter K

Clement Apffel
6-Dec-2009, 13:13
What I mean with "absolute 0 for GG alignment" is nanometric alignment, theoretically perfect alignment.
Absolute alignment in a word.
Do you really think viewcamera makers aim that precision?
Do you realise the cost of production this precision would involve?

Concerning the second point, again, you misunderstood what I mean.
“Apply the real precision you need” doesn’t mean: do not care about precision.

I know the misalignment of my holder / GG device to all 4 corners and center and its rough value, the direction of the potential derivation due to film not being flat.
And knowing all this, accordingly to some basic optics calculations and to some field tests under my condition of use, I know and I see that I am currently under my IQ standards:

I apply the precision I really need.

regards,
CA

kev curry
6-Dec-2009, 13:29
Well it does get you thinking and learning. So I just done the test outlined in the book ''Way Beyond Monochrome'' to determine if the gg and film plane are in proper alignment. The test was pretty simple and doesnt require special equipment.

Its done with a ruler a toothpick and a bulldog clip.

1. Take the back off the camera and load it with a film holder with the dark slide removed. The holder must have a sheet of film in the holder.

2. Lay the back of the camera flat on a table so that the inside of the holder containing the film is facing you.

3.Place the ruler on its edge across the holder . Place the toothpick vertically against the ruler (180*) and lower it until it makes contact with the film, then clamp it in place with the bulldog clip. This identifies the film plane location.

''After doing this with all film holders (both sides) leave the toothpick positioned for an average holder''.
(4).''Now remove any film holder from the camera back, and compare the average film plane with the ground glass location (see 2nd photo). If the toothpick just touches the gg, then no adjustments are required. Knowing that a sheet of regular writing paper is about 0.1mm/0.004'' thick provides a tool to quantify any offsets. If the toothpick touches before the ruler, then you could shim the gg with paper, but if there is an unacceptably large gap between toothpick and gg then professional machining of the camera back is required.'' (W.B.M)

Btw... this was with (my) gg changed to nearest the lens with fresnel on the viewers side. My gg needs a little shimming!... maybe the equivalent of 3 layers of writing paper. But its a vast improvement over the factory configured placement of the gg/fresnel combination!


Who's gonna be first to fry me for copy-write infringement:)

Darin Boville
6-Dec-2009, 13:41
I apply the precision I really need.


Indeed. Some of these tolerances bandied about are down in the thousandths of an inch, sometimes smaller.

Are we still talking about lightweight, wooden field cameras?

It would seem that a light wind would deform the camera alignment enough to swamp standards such as these. It would seem the pressure of the loupe against the ground glass would negate much of this precision. I never realized that my little 4x5 was such a fragile instrument!

In any event, those who favor measurement over experimentation have not uttered a word about magnitude or significance, or whatever term is preferred. There will always be error--but how much is too much?

Me? I'm still waiting for images (very few have been posted despite the fervor with which this topic has been debated). Perhaps we should move the discussion to dpreview in the interim?

--Darin

Bob Salomon
6-Dec-2009, 13:49
Now for the next problem, film isn't flat (digital sensors are) film sags. So how would you compensate for the average sagging of a sheet of film in the film holder under all conditions? Camera level, camera vertical, high humidity and heat, freezing cold, etc?

Just before Kodak introduced their first film holder for their original instant film they contacted us, as the Linhof distributor, as well as all of the then current USA view camera suppliers or manufacturers. Kodak's engineers wanted to know the film position settings of the different companies while they developed their holder. Some of you might remember that the original holder had problems maintaining sharpness in different cameras.

We contacted the factory and, like the other companies, supplied Kodak with the specifications. After a few months the Kodak engineers came back to us after they finished their project with some of the results. Of all of the cameras available at that time only two had a "0" position ground glass per Kodak's specifications. Neither was Linhof or Sinar. But the film holder made from these "0" specs would not supply optimal sharpness as film sags and the film sag was not factored into the holder. So it was re-designed.

The proof of the concept is that film is sharp where it is focused on, especially on an inclined plane. What is especially critical is that the film is positioned within the depth of focus of the lens and the more accurately this is done the better the overall sharrpness will be and as shorter lenses have less depth of focus the more critical this positioning becomes for people using shorter then normal lenses. So the average film sag most lie within the depth of focus of the shortest lenses you will use and the gg position has to be placed accordingly.

Mike1234
6-Dec-2009, 14:10
Ahh jeez... now we've gotta make vacuum backs to keep the film flat. Hey, Sandy!!! Wanna do the prototype??

Steve Hamley
6-Dec-2009, 14:16
Interesting Bob, thank you for posting. What is the average film sag, say for standard 7 mil film like Tri-X?

If one is checking backs, then the GG would need to be further than the "ideally flat" emulsion by the film sag if I understand your post correctly.

I'd also assume that sag is very small in 4x5 with relatively stiff 7-mil film, and more in larger formats since we all know the dangers of pointing ULF downward!

Cheers, Steve

JON BUTLER
6-Dec-2009, 14:30
Ken,
Did you load a sheet of film in holder when you took your measurements?
JON.

kev curry
6-Dec-2009, 14:34
yes

Peter K
6-Dec-2009, 14:53
What I mean with "absolute 0 for GG alignment" is nanometric alignment, theoretically perfect alignment.
Absolute alignment in a word.
Do you really think viewcamera makers aim that precision?
Do you realise the cost of production this precision would involve?
Sorry Clement, there is no "absolute 0 aligment" in any case. And of course there is no need to align a gg in the nanometer region.
And yes I know how to measure also in the nanometer area with micro-interferometers, electrons and x-rays.

And I know this has nothing to do with LF-cameras. So what?

Peter

Steve Hamley
6-Dec-2009, 15:17
Ahh jeez... now we've gotta make vacuum backs to keep the film flat. Hey, Sandy!!! Wanna do the prototype??

Mike,

We've always had to worry about that in formats over 8x10. If you search, you can find all sorts of solutions from adhesive (like Sinar), to vacuum backs, to homebrew solutions like a bit of honey or molasses (dissolves in pre-soak or developer).

Cheers, Steve

erie patsellis
6-Dec-2009, 16:45
Mike,
...to homebrew solutions like a bit of honey or molasses (dissolves in pre-soak or developer).

Cheers, Steve

Or, thanks to modern science, Post-It Restickable adhesive glue sticks (http://www.staples.com/3M-Scotch-Restickable-Glue-Stick-.20-oz/product_510818).


erie

Darin Boville
6-Dec-2009, 17:28
Or, thanks to modern science, Post-It Restickable adhesive glue sticks (http://www.staples.com/3M-Scotch-Restickable-Glue-Stick-.20-oz/product_510818).


erie

No way! I was just thinking that the sag problem would be easily solved if the sold the 3M glue by itself--I never imagined they actually did...anyone try this yet?

--Darin

Sal Santamaura
6-Dec-2009, 17:51
Ahh jeez... now we've gotta make vacuum backs to keep the film flat. Hey, Sandy!!! Wanna do the prototype??No need for Sandy to do that. Schneider's already been there in the late 1990s:

http://www.largeformatphotography.info/forum/showthread.php?t=373

and discontinued its product by 2001 for lack of sales:

http://www.largeformatphotography.info/forum/showpost.php?p=26418&postcount=15

It's all here in the archive. :)

Mike1234
6-Dec-2009, 18:56
No need for Sandy to do that. Schneider's already been there in the late 1990s:

http://www.largeformatphotography.info/forum/showthread.php?t=373

and discontinued its product by 2001 for lack of sales:

http://www.largeformatphotography.info/forum/showpost.php?p=26418&postcount=15

It's all here in the archive. :)

Kewl... it can't be THAT difficult to modify some standard DD's. Maybe I'll try it. :)

Renato Tonelli
6-Dec-2009, 20:44
Boy, do I feel tired... and more confused than ever. I may need to make an outline to make sense of all this. I don't know how I missed this thread before today, but it all started when I googled for a Chamonix dealer for a 5x7...

GPS
7-Dec-2009, 02:23
Boy, do I feel tired... and more confused than ever. I may need to make an outline to make sense of all this. I don't know how I missed this thread before today, but it all started when I googled for a Chamonix dealer for a 5x7...

OK Renato, I'll help you a little. The aforementioned problem (and the nonsensical and untrue explanations of it written on the Chamonix web site) concerns the Chamonix 45N-1 camera, not their 5x7 camera line. So far, at least. Feeling better?:)

Renato Tonelli
7-Dec-2009, 16:13
GPS - I am not feeling better but thank you for trying:) I'm going to do a little more research before I decide on which 5x7.

GPS
7-Dec-2009, 16:17
Would do the same in your shoes too...;-)

europanorama
5-Jan-2020, 08:50
"But this is all moot anyway if you just remove the fresnel, or place it between you and GG, or replace the stock fresnel with some other screen intensifier.
It's really not as big a deal as many people have made it out to be."

Yes it can be a very big deal if the camera designer designed the fresnel to be in front of the gg. If you just take the fresnel out and put it on top of the gg or just replace it with another behind the gg or just throw the fresnel away you will probably need the ground position of the gg adjusted as it expected a spacer the thickness of the original fresnel lens.

i like people who read the ignorants the "leviten". Had the very same "problem" ignoring the diffraction problem (at 11/16)in newly designed lens in newest Horizon S3Pro and other versions. proved it, showed it in pbase until they removed the thread. its still in archive but no proofs/images. unsharp is unsharp no matter what is said. i can sing a song was busy during weeks with Dora Goodman Zone Z1-bodies(3 versions) and proved the two they produced(Light and 200series are not calibrated to infinity.

europanorama
5-Jan-2020, 08:59
I had posted this information a few months ago:

Quote:
Re: Focusing problems with the fresnel groundglass on the Chamonix 45N-1?
I was a little baffled with this thread. Two people with the same camera having identical problems with a particular focal length lens. I would have thought that the Chamonix being a new camera the position of the gg/fresnel combination would have been tested. So I thought I would test my own Chamonix, and using mm ruler verify any small differences if they existed.

For a target I used a window mat on a mat board that would provide a bright line (reflecting the overhead light), and a dark line that would be a shadow from the overhead light. Both lines would be parallel to each other, and the target would also test flatness of the gg (i.e. there should be no change in focus of the parallel lines).

I checked three lenses, my 58mm Schneider XL, 90mm Linhof Scneider Angulon f5.6, and my Apo Sirornar S 135mm. All were tested with either the fresnel in the proper position, with it on top of gg, and no fresnel - just the Chamonix gg. I used a Scneider 6X loupe to check for focus.

With the 58mm lens the focal shift +0.5 mm with the fresnel in the proper place. With the 135mm lens the focal shift was +1 mm with the fresnel in the proper place. This should not make a big difference in depth of field unless shooting wide open I would think. However, with the 90mm lens the focal shift was +3.5mm with the fresnel in the proper place. There was no focal shift when the fresnel was placed on top of the gg. I have tried 2 other gg that I have, and made the same observation.

One possible explanation is the focal length of the fresnel is affecting the focus of 90mm lenses. I do not have another fresnel to test. But I think hereafter I will keep my fresnel on top.
End Quote:

I also followed up that I had put a Maxwell screen from another camera (that I had sold) on the Chamonix and saw no focus shift. I had a thicker cover glass so I cut shims (hose washers) for the gg hold-downs.

I honestly cannot see in any of my images that there is a focusing issue, but I generally stop down f22 or greater. I have had my camera almost two years. I think the only way this issue affects me is maybe where dof was critical and objects closest to me weren't as sharp as I may have thought - but that maybe operator error.

Mike
if the 90mm angulon has that much shift couldnt the smaller COC(if true) be the reason? smaller COC=shallow/less DOF= better resolution

europanorama
5-Jan-2020, 09:06
I just did some basic optical calculations and here are the numbers :

with a 150mm lens. when focused on a 5m away subject, a 1mm focus shift towards the user means a 86cm focus shift in the "object space"
and a 0.5 focus shift is a 47cm shift.

4m away subject, 1mm focus shift is a 56cm shift
and 0.5mm focus shift is a 30cm shift.
1. "5m away subject, a 1mm focus shift towards the user means a 86cm focus shift in the "object space"
meaning 5m minus 0.86m right?
2. can you give us the calculations how you got the other shifts also?
on Zone Z1 200series body is 0.84mm too short.resulting in focus-shift of 20cm at 3m towards shooter. 3m = 2.8m. 150mm lens.
is there a calculation rule? i could recheck that by comparing in Mamyia Universal Press/Super 23 cameras. lenses are in helicoids obviously.

europanorama
5-Jan-2020, 09:11
I just did some basic optical calculations and here are the numbers :

with a 150mm lens. when focused on a 5m away subject, a 1mm focus shift towards the user means a 86cm focus shift in the "object space"
and a 0.5 focus shift is a 47cm shift.

4m away subject, 1mm focus shift is a 56cm shift
and 0.5mm focus shift is a 30cm shift.
i will go the very same test with Sekor 150mm blue(razorsharp lens even fully open) of MUP/S23-system. its a the calibrated lens, was never off in my hands. only didnt have the values present when i repleid first.
i tested at 3 and 5m. shift stays at 0.84. shim-checked and verified. must dig out the values of 5m since i will not remove the shim or budy another body. Light version has a bit different shift. since i know that i will verify in real in this body too.