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View Full Version : Focusing problems with the fresnel groundglass on the Chamonix 45N-1?



joshdaskew
25-May-2009, 04:48
Hi, I recently bought a Chamonix 45N-1 and have to say it really is a lovely camera.. At the same time, I have bought a Schneider Xenotar 135mm 3.5 and plan to shoot portraits with this lens wide open. At some point I will buy a 150mm 2.8 ( although I have found focusing trickier enough with this lens ). After doing some tests with this camera I noticed that the focusing was way out and was pulling a foot or so in front of what was focused on the groundglass ( after receiving film back ). I borrowed my friends Linhof to test with the same lens and sure enough, on getting the film back, what I focused on was in focus. I contacted Hugo who in turn contacted the Chamonix factory and they told me that this was the first in the factories history to have this problem and that the the problem was related to the fact that I was using a lens like the Xenotar wide open and that the groundglass that comes installed as a default on the Chamonix is a fresnel and this is apparently known for having issues with fine focusing. So I sent my back off to China and they have sent me two groundglasses back, the original fresnel and a non fresnel ( to be used with these faster lenses wide open ). Has anyone ever come across such a problem or able to shed some light on it? I haven't had a chance to test this yet but I hope the problem is fixed by the new groundglass.. Any information anyone could provide would be fantastic. Thanks. Best regards Stefan

P.S Have used my friends account as I don't have one yet.

Brian Ellis
25-May-2009, 05:15
Some fine focusing difficulty is inherent in any Fresnel lens. One of the reasons people pay $250 and up for Maxwell screens is that they're the easiest Fresnels to focus, at least the easiest I've used and I've used most of them. That's also one of the reasons some people prefer a plain ground glass. However, it isn't normal to be a foot off. Is this your first LF camera or your first with a Fresnel screen? If so, my guess is you just weren't used to the Fresnel and so weren't focusing it properly (what kind of screen does your friend's Linhof have?). But it's hard to say much more until you've tested your new viewing screens. It's conceivable that you got a Fresnel lens that wasn't properly matched to the focal length of the lens you were using (e.g. they inadvertantly put a wide angle Fresnel on your camera and you weren't using a wide angle lens) but this doesn't seem too likely. You were using a loupe and a dark cloth, right? FWIW, the screen on my Chamonix was fine.

As an aside, you probably know that the widest aperture on many LF lenses is there mainly to assist in focusing. It isn't generally expected that it will be used to make photographs so you likely aren't going to get the best quality images using a 3.5 or 2.8 LF lens wide open.

mandoman7
25-May-2009, 08:06
The main concern is that the position of the film in the holder replicates the position of the ground glass surface when inserted, so the film is in the exact position of the surface that's used for focussing. This is something that should be checked with any newly acquired lf camera (micrometer). I've regretted shooting a lot of film and founding out afterwards about a discrepancy.

In my experience, fresnels often get weird out towards the edges with wide angles, but the center is usually pretty usable for focussing. I've never heard of a fresnel focussing differently with certain lenses. In this case, having more than one lens would help with diagnosis, as well as broadening the learning curve.

joshdaskew
26-May-2009, 04:34
Hi, Thanks for the responses, much appreciated! I will write back more when I have done some actual tests with the new groundglass but that won't be till early next week. Brian in response to your answer, I used to have a Linhof Technika 5 but I never used it with this lens. With the original fresnel groundglass on the Chamonix, I did a couple of tests. One comparison was to shoot with the Xenotar @ 3.5 and a Rodenstock Sironar - N I have @ 5.6. Both images came back with focus falling ahead of what I had originally focused on. Both images appear sharp on the ground glass and it is only when I got the film back that you can see the results. To be honest, I don't think it was that my focusing was out. When I compared it with my friends Linhof
( which I think is a non fresnel screen ) the object was spot on in focus when the film came back.

So as I said, will post some more when I have tested out the non fresnel variety with the Chamonix. Will be interesting......

As for shooting wide open, the look I am after is to have an extremely sharp drop of focus for portraits and this is the only way to achieve this.... How much of a degradation of quality are we talking here? I mean it is still 5 x 4 inch film right, so the quality has to be somewhat decent I would have thought?

As for the Maxwell screen, I have heard this recommended by a few people. Is this something that I would have to find to adjust or would I have to send him my camera for him to do. At this stage I am a little sick of sending my camera all over the world...

To Mandoman7, I am definitely aware of how important a ground glass screen is to be spot on with the film plane of your double dark slide, what is the best way to test this? I am not particularly technical.....

Ok, thanks again so much for your responses... Will post some more early next week. Best regards Stefan

joshdaskew
4-Jun-2009, 19:07
So after receiving a new back to my Chamonix 45N-1 with a non fresnel screen ( which I thought was fantastic customer service by the way - Thanks Hugo ) I have done some more tests with my Xenotar 135mm @ 3.5 and they have come back in focus with the non fresnel and out of focus with the fresnel type. Is this really just a case of me not being able to use the fresnel type properly? I mean, I intend to use this for portraits, so focus has to be spot on.. Any thoughts? Thanks to everyone who answered before. Cheers Stefan

Archphoto
4-Jun-2009, 19:32
I would try a fresnel lens on top of your GG.
In that way you would keep the acuracy of focusing that you have now.
I have the same set-up with my Sinar P2 and it works good.

Peter

NewBearings
30-Jun-2009, 06:24
The main concern is that the position of the film in the holder replicates the position of the ground glass surface when inserted, so the film is in the exact position of the surface that's used for focussing. This is something that should be checked with any newly acquired lf camera (micrometer). I've regretted shooting a lot of film and founding out afterwards about a discrepancy.



Howdy folks!

I have a new Chamonix 45 as well, and am having similar problems with focus @90mm.

The lens is a very good condition Rodenstock Gradagon-N MC 90mm F6.8
When focusing I'm using a dark cloth, a Rodenstock 4x Loupe placed in the center of the glass. The area appears sharp when focusing, but I'm finding the true focal point on film does not reflect that of the ground glass - it usually is at a point cloer to the camera than the point I have set focus. I've shot from f11 - f45. The smaller apertures fair better, but I need the option of being able to shoot wide open.

Hugo told me some people had some problems with the Fresnels @ 90mm. He suggested I remove it and just go with the GG. I haven't tried it yet. I have two other lenses: a Fujinon A 240mm F9 MC , and a late model Rodenstock APO-Sironar-S 135mm/5.6. Before I do anymore comprehensive tests with all lenses, I'm looking for more information to proceed.

Images with the 135mm seems to be a bit more on track with focus.

Since all my gear is new to me (except some old film holders), how does one "check" or calibrate a new LF field camera?

I would like to use a fresnel on this camera with all lenses. Will a different fresnel lens allow this?

I have some past experience with 4x5 & 8x10 rail cameras for portraits with studio lighting, but it's been half a dozen years and am a bit rusty.

TIA!

Gem Singer
30-Jun-2009, 07:36
Since this problem seems to be unique to the 90 Grandagon, un-screw the front element of the lens. There should be a thin shim washer between the lens element and the shutter.

If the shim is missing, it may be the cause of the problem.

I doubt that the Fresnel could be throwing the image out of focus if it has been mounted properly. That defect would show up no matter which lens you used.

A mis-match between the position of the ground glass and the position of the film in the film holder is a manufacturing problem. There are several ways to check for this. However, since the camera is new, it should be corrected under warranty.

Robert A. Zeichner
30-Jun-2009, 07:36
Ground glass/film plane coincidence is one of the most critical issues in getting sharp negatives. Theoretically, the frosted surface of the ground glass needs to be in precisely the same plane as the film would be when the holder is inserted into the back. Fresnels are sometimes used to brighten the image on the ground glass, but one must remember that a Fresnel is in itself, a lens. It will shift focus rearward by an amount roughly equivalent to 1/3 of its thickness. That said, if you want to use a Fresnel between the taking lens and the gg, you need to design that shift into the camera to make certain what you see on the gg is what gets onto the film. Many photographers who have grappled with adding a fresnel to a camera not designed for one, have simply placed it behind the gg, between the gg and your eyes. This solves the problem. The focal length of the lens can have a varying effect on perceived gg/film plane errors. Longer lenses projecting rays of light more closely parallel with one another may appear to withstand a bit more alignment error at the film plane than short lenses. Still, any gg/film plane error can be noticeable, even at small apertures, when compared to the same shooting set up in which that error as been corrected. I have gotten rid of Fresnels long ago and have been using finely ground home-made focusing screens with more consistent success. They are not as bright, but that just means I wait a little longer for my eyes to adjust under the dark cloth.

NewBearings
7-Jul-2009, 10:06
Thanks for the responses guys.
Placing the fresnel in front of the GG (or going without) has helped with the focus.

Ernest Purdum
7-Jul-2009, 11:37
I have a stick with slots to hold playing cards as targets. It was intended for use in teaching use of swings and tilts, but should be useful in diagnosing focus problems also. You would just place the stick at a moderate distance from the camera, focus on the middle card, then see which card is the sharpest on a negative or print.

Michael Rosenberg
7-Jul-2009, 17:12
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.

Mike

NewBearings
8-Jul-2009, 08:55
Mike,

Thanks for adding such a thorough test. I did not measure it in terms of mm on the camera. But did note the false focal point at about 25 feet (fresnel in place between gg & lens). This then focused about 30% closer with the fresnel removed (about 17 feet).

Hugo is aware of this and has informed the owner. It would be great if Chamonix had some sort of modification to the backs going forward.

Ivan J. Eberle
9-Jul-2009, 07:48
Regardless of the optical focus shift that may be happening here, doesn't the Chamonix 4x5 GG position physically change with removing the Fresnel? I'm not certain that it does (though most others with the GG to the back and the Fresnel in front do). If the Fresnel shims the GG-- that is, if the depth of the shoulder cut which the edges of the glass rest upon is correct only with the Fresnel-- simply removing it introduces the a problem of focus inaccuracy from having the the film holder and the GG now occupying different planes. So you'll need to shim it back to where it belongs.

For that you'll need either a depth gauge on a granite surfacing block, or a dial indicator that measures to .001" on a sturdy stand. Any decent machine shop will have the surfacing block. A decent dial indicator won't be much more than $50 these days. Any reasonably flat scrupulously clean surface like a polished marble countertop or formica will be probably be close enough for this task if doing it yourself.

The ANSI standard depth for a modern 4x5 film holder is .197". So, ideally, the GG should be set at this depth minus the depth of the film base you're using (typically .005 to .007"). Anywhere within +/- .007" is within the acceptable margin of the ANSI standard.

Michael Rosenberg
9-Jul-2009, 11:35
Ivan,

The fresnel is recessed; if you remove the fresnel the gg is sitting on a separate support so the depth is unchanged.

Mike

Robert A. Zeichner
9-Jul-2009, 12:24
If the Fresnel shims the GG-- that is, if the depth of the shoulder cut which the edges of the glass rest upon is correct only with the Fresnel-- simply removing it introduces the a problem of focus inaccuracy from having the the film holder and the GG now occupying different planes. So you'll need to shim it back to where it belongs.

And where it belongs without the Fresnel is different than where it belongs with the Fresnel, so your shims will actually need to be thinner than the Fresnel screen. If the Fresnel is .030" thick, a starting place for shim thickness would be around .020". Film tests at wide apertures with an appropriate step target are advised before pronouncing such a modification as ready to use.

For that you'll need either a depth gauge on a granite surfacing block, or a dial indicator that measures to .001" on a sturdy stand. Any decent machine shop will have the surfacing block. A decent dial indicator won't be much more than $50 these days. Any reasonably flat scrupulously clean surface like a polished marble countertop or formica will be probably be close enough for this task if doing it yourself.

Smooth and flat are two different things. This is not a measuring/machining job for someone without the correct tools and the knowhow to use them. In any case, you will not be machining anything, just adding shims. If you remove the Fresnel, measure it's thickness with a micrometer and buy some mylar shim stock in thickness equal to 2/3 the thickness of the Fresnel. You may have to stack some thinner shims to create the correct total amount of thickness. This is a starting point. Cut and sandwich the shims between the GG and the mounting pads and do some film tests.

The ANSI standard depth for a modern 4x5 film holder is .197". So, ideally, the GG should be set at this depth minus the depth of the film base you're using (typically .005 to .007"). Anywhere within +/- .007" is within the acceptable margin of the ANSI standard.

The ground glass needs to be right on the money and not just anywhere within the +/- .007" range specified for the film holder. Film holders are made of plastic and thin pieces of aluminum and will vary all over the place. If the ground glass is set to a position merely within, but near the extremes of the specified range of depth for a film holder, there is a good chance more than half your film holders may render unsatisfactory results. If you can't correct a GG positioning error with shim stock, send the camera back to the factory and have them make it right. You really don't want to be removing material from the pads of any camera.

Robert A. Zeichner
9-Jul-2009, 12:38
Ivan,

The fresnel is recessed; if you remove the fresnel the gg is sitting on a separate support so the depth is unchanged.

Mike

In cameras where the Fresnel is actually suspended in front of the GG as opposed to being sandwiched between the GG and mounting pads (Horseman 45FA is another example, although they do it by attaching the Fresnel with clips to the GG), you still have to move the position of the GG to get it in the correct position for use without a Fresnel. In the Horseman, the designer had the presence of mind to include shims between the GG and the mounting pads as part of the design so that if you wanted to remove the Fresnel, you could simply remove the shims as well to move the GG forward to the correct postion. In an instance where the GG is already sitting on pads without shims and where the Fresnel is sitting on a separate set of recessed pads, removing the Fresnel will necessitate machining down the pads on which the GG is sitting. My advice... don't go there.

Ivan J. Eberle
9-Jul-2009, 13:23
Robert, point well taken that the amount that the GG moves is not necessarily the thickness of the Fresnel lens as a shim. But the only ANSI standard that I've yet found is the median for the film holders, have yet to see a number for the distance from the gate to the GG. I've assumed it's either .190" or .192", the correct number being somewhat variable based upon the thickness of the specific emulsion in use (at least with filmholders like the standard 2-up darkslide having a film slot and no pressure plates).

Second is, how much difference does a couple of thousandths actually make at the film plane in practical use-- under what specific circumstances is it going to show up? I'd certainly expect it's much more critical with an Aero Ektar f/2.5 used wide open than with the typical f/5.6 or slower view camera lens stopped down to a taking aperture of at least f/11 (more likely f/22 for adequate DOF) for landscape. Can anybody point to a chart or give a formula for calculating depth of critical focus at the film plane for a given focal length, focusing distance, and aperture?

Realistically, can wooden field cameras or holders be produced in volume to within a repeatable tolerance of .007"? Agreed that stacked errors of say, a wooden back that's on the far side of the tolerance, with some swelling from humidity, coupled with a moisture-swelled wooden holder, could really begin to add up. It's not too hard to see why mid to late 20th Century technical designs began to be manufactured from more dimensionally stable materials like aluminum as soon as became practicable.

Also mentioned in another thread recently and still begging a satisfactory answer: Why are Fresnels ever put inside the optical path in the first place, if putting them on the outside (on top of the GG) achieves the same brightening effect and allows easier interchange for different focal length lenses?

Robert A. Zeichner
9-Jul-2009, 16:20
Robert, point well taken that the amount that the GG moves is not necessarily the thickness of the Fresnel lens as a shim. But the only ANSI standard that I've yet found is the median for the film holders, have yet to see a number for the distance from the gate to the GG. I've assumed it's either .190" or .192", the correct number being somewhat variable based upon the thickness of the specific emulsion in use (at least with filmholders like the standard 2-up darkslide having a film slot and no pressure plates).

While compensating for average film thickness is certainly a legitimate factor when aligning gg placement, I would still be very cautious about using the same +/-.007" tolerance for error as is used in the ANSI spec for (4x5) film holders. Suppose gg placement is .007" shallow and you insert a film holder that is .007" deep. Both technically meet the +/- .007" ANSI spec, but combined as a system, your film is now .014" away from the gg position. This, I assure you will be noticeable.


Second is, how much difference does a couple of thousandths actually make at the film plane in practical use-- under what specific circumstances is it going to show up? I'd certainly expect it's much more critical with an Aero Ektar f/2.5 used wide open than with the typical f/5.6 or slower view camera lens stopped down to a taking aperture of at least f/11 (more likely f/22 for adequate DOF) for landscape. Can anybody point to a chart or give a formula for calculating depth of critical focus at the film plane for a given focal length, focusing distance, and aperture?

In a word, plenty. A lot will depend on what focal length of lens you are using. Shorter focal lengths with converging rays at a greater angle to each other than with long lenses, have a shallower depth of focus requirement to achieve satisfactory sharpness. While closing the aperture down to smaller f stops will increase depth of field, it will not fully compensate for poor gg/film plane coincidence and I have the negatives to prove it. A "couple of thousandths" beyond the range of tolerance will throw you into noticeable softness.


Realistically, can wooden field cameras or holders be produced in volume to within a repeatable tolerance of .007"? Agreed that stacked errors of say, a wooden back that's on the far side of the tolerance, with some swelling from humidity, coupled with a moisture-swelled wooden holder, could really begin to add up. It's not too hard to see why mid to late 20th Century technical designs began to be manufactured from more dimensionally stable materials like aluminum as soon as became practicable.

While a bit more of a challenge, by using aged hardwoods, properly sawn and sealed and precision milling equipment, the expert makers can achieve surprisingly accurate results. I've never personally compared the dimensional stability of wood to aluminum, but I can tell you with a fair degree of certainty that aluminum is not the most dimensionally stable material when it comes to changes in temperature. This I have measured.


Also mentioned in another thread recently and still begging a satisfactory answer: Why are Fresnels ever put inside the optical path in the first place, if putting them on the outside (on top of the GG) achieves the same brightening effect and allows easier interchange for different focal length lenses?

This may have to do with protecting the ridged side of the Fresnel from scratching. These screens are made out of plastic.

With all the ways focusing errors can be generated (operator error when focusing, camera adjustments getting accidentally bumped, film buckling, film holders being a bit warped), the last thing you want to do is permanently stack the cards against ever getting a sharp negative by having your ground glass in the wrong place.

pocketfulladoubles
10-Jul-2009, 13:16
As for the Maxwell screen, I have heard this recommended by a few people. Is this something that I would have to find to adjust or would I have to send him my camera for him to do.

This is a great question. Has someone tried a Maxwell screen on the Chamonix yet, and if so, how did it fare with the 90mm lens focusing issue? Did you need to shim it or make any adjustments to calibrate the focal plane?


Edit: Oh well, neuroticism got the best of me so I broke down and just ordered the Maxwell Ultra Brilliant screen. I'm also likely sending it in to have the focal plane calibrated. I'll let you know how it goes.

Mark Jaremko
11-Jul-2009, 00:05
This answers a lot of my questions, I've had a very frustrating month with this problem. My Chamonix 45N arrived in May, and most of my photographs are very much out of focus. I shoot mainly landscapes, so am focusing on infinity, but am also shooting them at night, so need the faster apertures, or else I'm standing for 45 minutes to take a single photograph. I know they're in focus on the GG, this I can see quite clearly through my loop, but so far only shots at F16 are beginning to approach being in focus.

One additional problem I've noticed is that the film plane and GG/Fresnel plane are not parallel. I have about 20 sheets, all shot with various lenses, various new film holders, and at various apertures and all of them show the image more in focus on the far right side and less in focus on the far left side. This consistency seems to indicates a problem worse than just Chamonix not compensating for the Fresnel thickness in placing the GG. Given that I seem to be the third person in a few weeks to notice this, has anyone else seen this?

I do trust that Chamonix will help resolve this (I only emailed Hugo about this today), but folks have mentioned about sending their cameras in to be "calibrated". Who does this sort of calibration?

JON BUTLER
11-Jul-2009, 01:46
I think you must be unlucky.
I've been been using 4x5 cameras for decades and are now using two Chamonix cameras and I think they are the best all round 4x5 available on the market today.
No problems with focusing, the back and screens are interchangeable between the two and the focus still spot on.

JON.

NewBearings
11-Jul-2009, 01:49
Mark,

Try placing the fresnel on the external GG surface and using critical focus wide open with the same night scenes, but in daylight. Use a loupe to see if the focus plane is flat on the gg. Also check to see if your film carriers are sitting flat on all four edges when in the camera.

What lenses have you used when having focus trouble?

I did have a similar (uneven) problem with some images with my 90mm Rodenstock with the fresnel between lens and GG. I'm still running tests, so too soon to tell about flatness of film back.

Paul Droluk
11-Jul-2009, 10:00
One additional problem I've noticed is that the film plane and GG/Fresnel plane are not parallel. I have about 20 sheets, all shot with various lenses, various new film holders, and at various apertures and all of them show the image more in focus on the far right side and less in focus on the far left side. This consistency seems to indicates a problem worse than just Chamonix not compensating for the Fresnel thickness in placing the GG. Given that I seem to be the third person in a few weeks to notice this, has anyone else seen this?

I only recently acquired my first wooden field camera, a Chamonix 5x8. I've always used metal cameras, like the Toyo 45AII, but wanted to get a feel for what the wooden camera experience is all about. While the Chamonix does seem decently made (I haven't put a micrometer to it) I'm really amazed by the total lack of "0" detents. It means you have to zero every aspect of the camera via GG inspection, for each and every new shot! While I'm very much into the slow-down mantra of LF shooting, having to go through this tedium for each new set up is a bit over the top... IMHO.

pocketfulladoubles
12-Jul-2009, 09:11
I do trust that Chamonix will help resolve this (I only emailed Hugo about this today), but folks have mentioned about sending their cameras in to be "calibrated". Who does this sort of calibration?

Bill Maxwell referred me to Bill Moretz of Pro Camera, Inc. The screen is going straight to him for installation.

Mark Jaremko
12-Jul-2009, 22:31
Thanks everyone for the information, this was my first post as Iím quite new to the LF area, this being my first 4x5 camera, so Iím certainly doing a lot of learning, and the information on this forum has been extremely useful.

The two lenses that Iíve done all my testing with are :
Schneider Super Angulon XL 90mm f5.6
Schneider APO-Symmar 210mm f5.6.

Most of my tests were done with the 210. It turns out that my subject, distance cityscapes, is an ideal test subject, the distance city light make tiny pin point sources of light that are easily seen and focused on in the GG, and similarly quite easy to tell if the resulting film is in focus.

I took the GG holder apart and broke out the digital micrometer to take some measurement. I think I might have found a potential problem, assuming my numbers are correct. Hereís what I found.

I measured an approximate distance from edge of film holder to GG plane to be 4.745mm on the left side, and 4.815mm on the right side (based on an average of 10 measurements). Being a difference of 0.069mm, which Iím not sure is significant.

My understanding from an earlier post is that the specification for a film holder is 0.197Ē, which comes out to 5.00mm. I decided to see how accurate this was by measuring one new Fidelity Elite holder. I came up with measurements of about 4.93mm after many samples. Itís difficult to measure this distance with a standard micrometer due to ease of introducing flex in the plastic holder. This was only a sample size of 1 holder and so not statistically relevant, and itís pretty close. Letís go with 5.00mm as the correct distance.

If thatís the case, then my GG was held anywhere from 0.187mm to 0.255mm closer to the lens than the film plane. Then you have to compensate for the Fresnel, which is between the GG and the lens.. The Chamonix Fresnel was a bit harder to measure, after 10 or so measurements, I saw values anywhere from 1.65mm to 1.85mm at difference areas around the lens. Another post (If I understand correctly), suggested that the effective focal plane is 1/3 the thickness of the Fresnel closer to the lens due to the Fresnel acting as a lens itself. If thatís the case, and we assume the 1/3 compensation value posted previously, then weíre at 1.77mm (average thickness of my Fresnel) / 3 = 0.59mm.

Now the difference between film plane and GG plane grows to 0.775mm and 0.845mm, which seems like it would be very significant.

So I removed the Fresnel. Unfortunately, with a Chamonix 45N, you can not mount the Fresnel over the GG because itís actually shorter than the GG, and sits on a recessed ledge in the holder (to allow the GG to independently sit a fixed distance with or without the Fresnel). I need to find someone who can cut me a larger Fresenel.

I then built 0.20mm of shims to places to move the GG surface back by that amount. This turned out to be easy as sheets of clear transparency film (the kind you use in printers), was 0.100mm, and very consistent across all the measurements I took. I put the GG holder back together, and at 1am last night, headed out the door to shoot some film. I found the 90mm impossibly difficult to focus at night without a Fresnel, only the very center of the GG had near enough light to focus with, anything outside of dead center was just pure black (unless I tilted my loupe back towards center, but then I was looking at a distorted and highly out of focus image).

Incidentally, I found one design flaw with the GG clips on the Chamonix. The screws are too long, and if you over tighten the screws when reassembling the GG clips, youíll easily push them through to the other side of the wood GG holder. The resulting ďdentĒ in the wood will easily add 0.1mm of error, so you have to fix this before mounting the holder back into the camera.

Iíll process the film and see what the results are. Thanks again for the help.

NewBearings
13-Jul-2009, 00:59
Mark,

I'm not sure why you would need to shim the GG on the Chamonix - unless it is truly uneven and the shims are just on one or two sides for balance. On my film back the frsenel sits in a recessed space. Removing the fresnel does not change the placement set of the GG. There is also enough space on the external side of the GG to place the fresnel. Though some way of clipping it needs to be devised. I'd suggest some small wire clips and nylon washers for the moment. (This is my momentary solution).

I'd like to see Chamonix address this, hopefully with either a modification to an existing back or a redesign of the backs. (Hugo does have the url for this thread).

With regard to the wood screws. Of course having a machine male and female would allow regular interchange of the screens. Wood with metal will eventually wear the holes with regular service. Having several backs with different screens (if needed) is a solution. Whenever working with wood, plastic, or softer metals and steel fitings it is always advised to take care in tightening to prevent damage and buckling of the softer material.

I don't have enough understanding of the tolerances on these backs to address your other technical observations on measurement. Perhaps someone else who has this wisdom (and by chance also owns a Chamonix 45) will weigh in. I hope to run a few more tests in the next week with all 3 of my lenses. Thanks for your input.

Mark Jaremko
16-Jul-2009, 02:07
It seems that removing the Fresnel and adjusting the GG location with 0.100mm shims (to line up at 5.00mm) has fixed the problem. My chromes are absolutely sharp when shot wide open (f5.6). I'm glad I bought that digital micrometer last year.

Darin Boville
24-Sep-2009, 22:06
I saw mention of this thread elsewhere here and realized that I'd never done a focus check on my Chamonix 4x5. Here's a Polaroid with a 150 5.6 with the focus point right on the five-inch line. It looks good to me. Perhaps the focus issue is not widespread?

http://www.boville.net/Focus_Test.jpg

--Darin

NewBearings
25-Sep-2009, 13:07
It seems that removing the Fresnel and adjusting the GG location with 0.100mm shims (to line up at 5.00mm) has fixed the problem. My chromes are absolutely sharp when shot wide open (f5.6). I'm glad I bought that digital micrometer last year.

I was able to get the same (sharp focus) result by just removing the fresnel. Though I am now looking to replace the entire GG with either an Ebony or a Maxwell.

newmoon2night
27-Sep-2009, 01:48
I saw mention of this thread elsewhere here and realized that I'd never done a focus check on my Chamonix 4x5. Here's a Polaroid with a 150 5.6 with the focus point right on the five-inch line. It looks good to me. Perhaps the focus issue is not widespread?

http://www.boville.net/Focus_Test.jpg

--Darin
Did you intend to post a shot with the 5" line?! I presume the 5" line was spot on focus?

IanG
27-Sep-2009, 04:25
You just quoted Darin as saying "Here's a Polaroid with a 150 5.6 with the focus point right on the five-inch line. It looks good to me."

:D

Ian

willwilson
23-Oct-2009, 22:13
Easy fresnel fix for Chamonix 45-N1, see photos for details.

1. Bend and cut to length paperclip holders. I used a pair of needle-nose pliers.
2. Install fresnel with the grooves toward the ground glass.
3. Insert paperclip holders under ground glass holding washers.
4. Re-attach ground glass holding washers. (Be careful with those tiny screws you could very easily strip the hole in the wood out)
5. Enjoy a brighter screen again! That is in focus!!!

Two paperclips on the diagonal are plenty to hold the fresnel in place, although you could use four if you wanted to. The protector plate attaches just a little more snug, but works just fine.

joshdaskew
26-Oct-2009, 07:50
Wow!! I have just stumbled across this old post after thinking it ended after one page! Four pages later!! Since my earlier post, I have just been using the plain GG (which Hugo sent me when I first noted the problem) and haven't had any issues with focus, apart from the fact that of course I would like it to be brighter now. Am thinking of also getting a Maxwell screen and was just wondering if I can send him the back that I had the original issue with (Groundglass/fresnel screen combo) or if I should really send him the back that I have been using, that has had good focus (without the fresnel). Have Chamonix accounted for the fresnel in determining where the groundglass is positioned? Or have they neglected this fact and this is the reason why people are having focus issues? Also, what is the best way of taking the fresnel out? Is it just glued in or something like that? Is it easy to put the groundglass back without affecting focus accuracy? Ok, Thanks for the responses. Best Regards Josh

willwilson
26-Oct-2009, 09:05
You don't need a new ground glass or focusing screen. The original Chamonix fresnel is not glued in. All you need to do is carefully remove the four screws that secure the ground glass and fresnel in place. Remove the fresnel from underneath the ground glass. Then replace the ground glass. After that you can follow my instructions above. Screen is about the same brightness as before. The plastic screen will scratch more easily so be careful using a loop on it.

I never had noticeable problems with 135mm and longer lenses although I imagine there was a measurable error. I have had significant problems with my 75mm. Not anymore!

I wish we could get some type of actual solution from Chamonix. This is a pretty big screw-up on their part.

Steve Hamley
26-Oct-2009, 09:52
Just curious, but what do you mean "actual solution"? Several people have mentioned something similar but they never state what it is they actually want Chamonix to do.

Chamonix posted recommended fixes on their website. According to the information posted, the back is made correctly for a standard GG just like most every other currently available view camera, they just improperly stuck a fresnel in front of it.

Cheers, Steve

Mike1234
26-Oct-2009, 09:59
Just curious, but what do you mean "actual solution"? Several people have mentioned something similar but they never state what it is they actually want Chamonix to do.

Chamonix posted recommended fixes on their website. According to the information posted, the back is made correctly for a standard GG just like most every other currently available view camera, they just improperly stuck a fresnel in front of it.

Chamonix needs to modify all existing cameras so that they focus properly with the fresnel installed correctly. It's a matter of shaving a precise amount off the edge-seat on which the inner fresnel rests. The cameras came with fresnels and they should work properly with fresnels. Posting customer fixes is okay but it should be as an "option" at the discretion of the customer. If they don't support their product, as in a "recall" with free two-way shipping, they lose much credibility, IMHO. In fact, I'm not buying a Chamonix product until I see what they do about this. I'm thinking Shen-Hao at the moment but I'm still on the fence as I do like the Chamonix design better. I'll bet Canham wouldn't leave the fix up to the customer.....

Steve Hamley
26-Oct-2009, 10:31
Mike,


It's a matter of shaving a precise amount off the edge-seat on which the inner fresnel rests.

O.K., that I might argue with; it isn't consistent with how I understand an "unfrosted" fresnel to work. You'd still have a Nth power lens in the optical path and the image-forming surface behind it would be in the same place. So that wouldn't work, right?


The cameras came with fresnels and they should work properly with fresnels.

Amen.


Posting customer fixes is okay but it should be as an "option" at the discretion of the customer.

Yep, and if I were Chamonix, I wouldn't really want the customer fixing the problem unless they were completely comfortable doing so.

But Chamonix's response I think has broader implications. How many people would buy a used one knowing that it needs fixing - in other words, what does it do to resale value? If the resale value is significantly reduced, can first line sales be far off?

Cheers, Steve

GSX4
26-Oct-2009, 12:19
That's another reason the chamonix is so cheap compared to other cameras..... No support from the factory. It's a big cock up from their end and they have no plans to fix it. Only to merely tell you how to work around it.

Mike1234
26-Oct-2009, 13:13
O.K., that I might argue with; it isn't consistent with how I understand an "unfrosted" fresnel to work. You'd still have a Nth power lens in the optical path and the image-forming surface behind it would be in the same place. So that wouldn't work, right?

Hi Steve,

It's not the frosted/unfrosted fresnel that's the issue. It's the extra spacing caused by the fresnel when it's installed between the GG and the body. If correct focus occurs with it removed and the GG is move forward the thickness of the fresnel then the factory failed to account for the thickness of the fresnel when they machined the body. Or am I missing something? :)

Steve Hamley
26-Oct-2009, 13:58
Mike,

I don't have a Chamonix, so maybe I'm missing something. I'm under the impression that the fresnel sits in it's own little shelf and the GG with the image forming surface also sits in one, albeit a larger shelf. See post #15.

So the only thing shifting the focus is the power of the fresnel itself. Removing it leaves the GG in the same place.

Cheers, Steve

Steve Gledhill
26-Oct-2009, 13:59
Easy fresnel fix for Chamonix 45-N1, see photos for details.

1. Bend and cut to length paperclip holders. I used a pair of needle-nose pliers.
2. Install fresnel with the grooves toward the ground glass.
3. Insert paperclip holders under ground glass holding washers.
4. Re-attach ground glass holding washers. (Be careful with those tiny screws you could very easily strip the hole in the wood out)
5. Enjoy a brighter screen again! That is in focus!!!

Two paperclips on the diagonal are plenty to hold the fresnel in place, although you could use four if you wanted to. The protector plate attaches just a little more snug, but works just fine.

Neat and tidy technical solution Will. Here's mine with duct tape ...

GSX4
26-Oct-2009, 14:13
correct Steve, the GG and fresnel rest on seperate ledges, but the effect of the fresnel lens does shift the focus away from nominal focus on GG. In the factory the focus is calculated without the fresnel attached and the gg ledge is adjusted accordingly. Now add in the fresnel in front of the GG and its enough to shift focus quite noticably. It should have been measured and adjusted with the fresnel attached.


Mike,

I don't have a Chamonix, so maybe I'm missing something. I'm under the impression that the fresnel sits in it's own little shelf and the GG with the image forming surface also sits in one, albeit a larger shelf. See post #15.

So the only thing shifting the focus is the power of the fresnel itself. Removing it leaves the GG in the same place.

Cheers, Steve

Steve Hamley
26-Oct-2009, 18:36
Thank you Andrew,

I think I understand the technical issues now. The confusion in the thread seems to exist because people are talking about several different things at once, technical and economic (support) issues.

The solutions seem to be:

What can the user do?

1) Remove the fresnel. The GG is in the proper place.

Drawbacks: the image is now quite a bit darker.

2) Remove the Chamonix GG and Chamonix fresnel, and install an aftermarket fresnel IN PLACE OF THE GG (not the Chamonix fresnel) that has a "frosted" side facing the lens, so that the image-forming surface is in the same place as the Chamonix GG. Then install a cover glass to protect the fresnel. The fresnel is now effectively BEHIND the GG and the image-forming surface is in the same (correct) place. This is the "Ebony" or "Maxwell" option referenced on the Chamonix website.

Drawbacks: You pay unless Chamonix does.

3) Have someone re-mill the GG frame to work with the existing fresnel.

Drawback #1: Shipping and wait if you have Chamonix, Ritter, etc do it, cost if Chamonix doesn't do it gratus.

Drawback #2: If the back is re-milled to relocate the GG, it will no longer work with a plain GG or with the Ebony/Maxwell option mentioned above, and may not work with any other fresnel of a different power.

Note: Personally I would not modify the back to be non-standard and to work only with a fresnel of unknown characteristics.

So you just have to pick which one you want.

Unless Chamonix picks up the tab, you're going to get darker on the screen or lighter in the wallet if you want accurate focus under all conditions.

I'm not sure what Chamonix does at this point. They're sort of, well, screwed, but they did it to themselves. I'd probably offer what Mike suggested, send us the frame/camera and we'll fix it and pay shipping. I don't think they can send out "fix it" kits since many of the cameras have been re-sold so they wouldn't know who really has one, or for that matter, if all the cameras have the same problem given the QA/QC. As a business entity, Chamonix clearly needs to make the quality assurance/quality control a little more balanced with the apparently superb craftsmanship they exhibit.

Cheers, Steve

willwilson
26-Oct-2009, 20:21
Steve, I agree with all of your points. You neglected to mention...

4) Remove the factory installed fresnel and install it in its proper place on the outside of the ground glass, the photographer side, grooves toward gg (see mine or Steve Gledhill previous posts).

My suggestion to Chamonix would be to supply customers with some type of modified groundglass washer/holders that will hold the fresnel securely on top of the existing ground glass. This could be installed by the customer and would be an easy solution for all. Modifying the back is out for me. I actually prefer that it is standardized and can accept other screens easily. The new part could be something similar to what I used with the bended paperclips or an entirely new part that replaces the old gg washer/holder part.

I have had excellent service customer service from Chamonix and Hugo. They are a small business. I am sure they are very concerned about this problem and are working diligently. I fully expect that a solution is forth coming.

Steve Hamley
27-Oct-2009, 05:28
Will,

I didn't consider that as a long-term option because the fresnel is plastic and would eventually get scratched up. But you're correct, it will work.

I've had good business dealings with Hugo also (whole plate holders), but I'm not sure how much say he will have in the matter. But my guess is that you're right and a solution will be forthcoming.

BTW, if you're ever over Knoxville/Smokies way, look me up.

Cheers, Steve

iamjanco
27-Oct-2009, 06:23
As a non-Chamonix owner who almost bought a 45N-1, given the remedy for the focusing issue provided by Chamonix thus far, I've a concern for would-be Chamonix buyers. There's no doubt that the 45N-1 is a beautiful and stable camera, and like others here I'm fairly sure the folks at Chamonix are very concerned about it, but the statements on their website about the issue and the fact that they state the issue will be fixed in their forthcoming models, leads me to believe there's little Chamonix thinks it can do other than provide a work-around for owners of the current 45N-1. I've seen other used 45N-1s for sale here on the forum and there's at least one currently up for auction on the bay site. Also, I'm not sure if the issue affects the other camera models they sell, but I'd be wary if I was considering buying one. That would also be my recommendation to anyone else in the market for a new or used Chamonix, unless the seller could prove that their copy wasn't impacted by the issue.

Now, I'm not trying to upset anyone at Chamonix or any Chamonix owners. But it's evident that Chamonix missed the issue in any testing they did of the design, and I don't know if the issue in question affects all of their cameras, is limited to the 45N-1, or just one or more specific manufacturing runs of the 45N-1. But the bottom line from the perspective of common sense is that Chamonix needs to provide a fix that fully satisfies current owners of a 45N-1 experiencing the issue. Until they do that, the quality standards they employ, its control, and their level of customer service will all be in question.

And those, as many of us well know, can make or break a company.

Jan C.

Mike1234
27-Oct-2009, 08:31
Well, I'm not buying one unless they'll sell me one without their GG at a substantial discount so I can use some of those funds to buy a nice third party screen... or if they'll install the other screen at a discounted price. Also, until this is fixed and they've dealt fairly with their customers I'll never buy a Chamonix product. For me it's a matter of "trust" and I no longer trust Chamonix.

GPS
27-Oct-2009, 13:10
...
But Chamonix's response I think has broader implications. How many people would buy a used one knowing that it needs fixing - in other words, what does it do to resale value? If the resale value is significantly reduced, can first line sales be far off?

Cheers, Steve


Steve, I agree with all of your points. You neglected to mention...

...
I have had excellent service customer service from Chamonix and Hugo. They are a small business. I am sure they are very concerned about this problem and are working diligently. I fully expect that a solution is forth coming.

Steve,
you're surely right in your instinct. Unfortunately, the problem and its implications are even far broader than mentioned in this thread. Why? According to another thread the very same problem for the very same reasons exists also on their 5x7 and 8x10 cameras of the same kind as the 45N-1. Despite this fact Chamonix has not warned the owners of these cameras about the problem. Not with one word on their site! Useless to say these cameras sell for 2-3.000 $ a piece!
What does it mean? Unless Chamonix is kicked into their face they will continue to play their game of "unseen doesn't exist" and sell happily cameras with the serious design problem with the same ingenuity as they did, up to now, with their 45 model.

Now go and talk about the "good will" of Chamonix to correct the problem...
At what a date a new announcement on the Chamonix cameras site...? After more kicks?

Mike1234
27-Oct-2009, 13:51
Chamonix had better address this immediately and with full resolve or they'll soon lose all sales and it's goodbye Chamonix. Too bad. They seem to be excellent cameras other than that one major flaw. Hmm... maybe I should try to find a few hundred thousand bucks and buy up their inventory at 25 cents on the dollar at auction when their business folds. Then I can have them all properly adjusted and sell them "with full support" at nearly their current pricing. Now... where did I leave my wallet??

Hugo Zhang
27-Oct-2009, 14:05
Hi Guys,

As I annouced in our website a few weeks ago, we are fully aware of this problem and are working to solve it. We apologize for the inconvenience this has casued to our users. Our designer has returned back to the factory from a long trip in Tibet and we will look at every possible solutions to this and we expect to annouce something soon in our website.

Everybody should know that we use fresnel lenses only on our 45 cameras. Other camera models are not affected since there are no fresnel lenses on them. Rumors of this problem in other models were invented by one person who has never used our camera.

Thank you for your support and patience!

Songyun
27-Oct-2009, 14:11
According to another thread the very same problem for the very same reasons exists also on their 5x7 and 8x10 cameras of the same kind as the 45N-1.
According to what? As far as I know fresnel is only supplied with 45N-1 cameras. 57 and 810 has ground glass only. (I have an 810, which doesnt have the slot for fresnel)As mentioned by a lot of ppl here, as long as you removed the fresnel, the problem is solved. You can bash Chamonix as much as you can, but get your fact straight!

Mike1234
27-Oct-2009, 14:27
Hugo,

Thank you for posting a reply. Will Chamonix offer a solution to remediate this issue for all existing cameras with this problem at no cost to the customer?

GPS
27-Oct-2009, 14:46
According to what? As far as I know fresnel is only supplied with 45N-1 cameras. 57 and 810 has ground glass only. (I have an 810, which doesnt have the slot for fresnel)As mentioned by a lot of ppl here, as long as you removed the fresnel, the problem is solved. You can bash Chamonix as much as you can, but get your fact straight!

According to the thread "focusing error", in the post n.16 by shadowleaves:

Ok, here comes THE answer....

This a design fault that exists on EVERY chamonix camera that uses a Fresnel, namely the 045n1, 057n1, and a few other models. YES, your 045n1 does have this focus shift.

I should have posted this in a separate post. I posted a while ago about this in a Chinese forum, that I did a thorough investigation into the focusing error of Chamonix 045n-1 cameras. My conclusion is that clearly the factory alignment calibration is done without fresnel on the ground glass (which was confirmed during my chat with Mr Xiang Yu, the owner of Chamonix and designer of all Chamonix cameras), yet their cameras are shipped with a fresnel placed between the ground glass and the lens.

This apparently causes the focus shift, usually about 1/3 of the thickness of the fresnel.

The problem can be easily illustrated by this pic. I drilled a hole in the center of the fresnel of 045n1, and capture the focusing results using my D50 camera and a macro lens. Clearly, the fresnel is the only cause of the focusing shift. If I focus through the hole that I drilled, or without fresnel completely, the focus will be perfectly accurate.

This in my opinion is the biggest fault in 045n1's design. I communicated with them about this, but unfortunately they think the users are going to use below f/32 for landscape anyway so it won't be a big practical problem in their opinion. I'll leave that up to you guys to decide whether you want to drill a hole in the fresnel or to remove it completely or to live with the focus error.

GPS
27-Oct-2009, 15:05
Hi Guys,

...
Everybody should know that we use fresnel lenses only on our 45 cameras. Other camera models are not affected since there are no fresnel lenses on them. Rumors of this problem in other models were invented by one person who has never used our camera.

Thank you for your support and patience!

Hi Hugo,
everybody would surely know if somebody like you cared to correct the error (see the mentioned thread) when posted. Pity that you knew about the posted error and its source and let it be...

GPS
27-Oct-2009, 15:11
Hi Guys,

...
Everybody should know that we use fresnel lenses only on our 45 cameras. Other camera models are not affected since there are no fresnel lenses on them. Rumors of this problem in other models were invented by one person who has never used our camera.

...

??? Shadowleaves seems to speak as a person who has and uses the camera ... See his post.

Songyun
27-Oct-2009, 15:54
??? Shadowleaves seems to speak as a person who has and uses the camera ... See his post.

He has 045N-1 but not 057N-1.

iamjanco
27-Oct-2009, 16:01
The only cameras spec'd out with a fresnel on Chamonix's web site are the 4x5 & 5x8. That's not to say the others don't ship with a Fresnel, just to say that only these two models appear to do so.

Jan C.

shadowleaves
27-Oct-2009, 16:05
??? Shadowleaves seems to speak as a person who has and uses the camera ... See his post.

I only have 045N1. I've not used any Chamonix 5x7 models so my experience applied for 45N1 only.

GPS
27-Oct-2009, 18:23
I only have 045N1. I've not used any Chamonix 5x7 models so my experience applied for 45N1 only.

"This a design fault that exists on EVERY chamonix camera that uses a Fresnel, namely the 045n1, 057n1, and a few other models. YES, your 045n1 does have this focus shift."

Can you explain??

GPS
27-Oct-2009, 18:50
Hi Guys,

...
Rumors of this problem in other models were invented by one person who has never used our camera.

Thank you for your support and patience!


He has 045N-1 but not 057N-1.

The fact that he's got the 045N-1 still contradicts Hugo's affirmation -"one person who has never used our camera"...

GPS
27-Oct-2009, 18:54
Hi Guys,

...Everybody should know that we use fresnel lenses only on our 45 cameras.
...QUOTE]

[QUOTE=iamjanco;521661]The only cameras spec'd out with a fresnel on Chamonix's web site are the 4x5 & 5x8.
...

Jan C.
???
Who's right here?

GPS
27-Oct-2009, 19:09
Hi Guys,


Everybody should know that we use fresnel lenses only on our 45 cameras. Other camera models are not affected since there are no fresnel lenses on them.
...


After checking that on the Chamonix site - indeed, Hugo, you're wrong. The 5x8 Chamonix cameras also have the Fresnell screen with it's faulty design. When "everybody should know" as you say, why don't you know???
Why didn't Chamonix warn the owners of this camera about it's problem at the same time when they announced the problem on the 4x5 camera?
Why do you say only the 4x5 cameras are affected with the problem?
Does indeed Chamonix need kicks to get to the bottom of this manufacturing problem in all of their affected cameras?

GPS
27-Oct-2009, 19:17
Hi Guys,

As I annouced in our website a few weeks ago, we are fully aware of this problem and are working to solve it. ...
Everybody should know that we use fresnel lenses only on our 45 cameras.
...

No, Hugo. You're NOT fully aware of this problem - you don't even see that your 5x8 Chamonix cameras also have the fresnell - and the problem! You're the first who should know it - if you "are working to solve it"!

Hugo Zhang
27-Oct-2009, 19:54
Sorry, I was not aware of this error of stating that our 58 camera has a fresnel lens. I will have this error corrected very soon. Again, only our 45n-1 camera comes with a fresnel lens.

shadowleaves
27-Oct-2009, 20:18
"This a design fault that exists on EVERY chamonix camera that uses a Fresnel, namely the 045n1, 057n1, and a few other models. YES, your 045n1 does have this focus shift."

Can you explain??

Sorry about the confusion. I was told by a reseller in China that 057n1 has fresnel some time in 2008 if I remember correctly. If Hugo says 057n1 has no fresnel, then it has not. He is certainly official on this matter.

Darin Boville
27-Oct-2009, 20:58
O.K., folks. I'm seeing a lot of excitement on this thread about focusing errors but I still don't feel we've nailed down how exactly the error is manifesting itself and if it is widespread--and how to test for it.

Here are things that are confusing me:

Many people are saying that it only shows up at 90mm or shorter--yet the first person to raise the issue was using a 135mm (Schneider Xenotar 135mm 3.5). Later the OP mentions the same problem with a "Rodenstock Sironar - N I have @ 5.6." The OP implies that he was shooting at portrait distances.

Many posts here suggest that the problem is that the groundglass/fresnel combo is not spaced properly. If that is the case am I right to assume that the problem would be most pronounced at close distances? That we could do a test simply by focusing on an object a foot or two away?

How widespread is this? I went through the threads and though there is a great deal of strong language I count only a small number of actual problem cameras--perhaps three or four?

It would be great to agree upon a test method--it would be even better if people could post images showing the problem.

--Darin

NewBearings
28-Oct-2009, 01:49
No, Hugo. You're NOT fully aware of this problem - you don't even see that your 5x8 Chamonix cameras also have the fresnell - and the problem! You're the first who should know it - if you "are working to solve it"!



GPS - Just for the record, I have found the customer service Hugo has provided to be above and beyond at every step of the way. If only other business provided such great service as Hugo.


If you are really upset with the Chamonix I'm almost certain you could sell it at or close to cost and buy something else. Maybe an Ebony?

GPS
28-Oct-2009, 02:15
GPS - Just for the record, I have found the customer service Hugo has provided to be above and beyond at every step of the way. If only other business provided such great service as Hugo.


If you are really upset with the Chamonix I'm almost certain you could sell it at or close to cost and buy something else. Maybe an Ebony?

NewBearing - Just for the record, I and everyone who can read this thread have found that Hugo, who wrote "what everybody should know" didn't know himself about the error on Chamonix site. How great service in business that is I leave for everyone to judge.
As for your advice for people that are upset with the Chamonix - check Hugo's comment - although not entirely satisfactory yet he will work on the solution that seems to be much better than yours. Your's, from a business point of view, is nonsense.

Patrick Dixon
28-Oct-2009, 03:03
GPS, do you actually have a Chamonix, or are you just trying to stir up shit?

Dave Jeffery
28-Oct-2009, 05:47
There is still no need to spend a lot of money on a really nice camera that you will really enjoy working with for over 20+ year though. One could save $100 a year : )

Sal Santamaura
28-Oct-2009, 08:30
While I understand the frustration caused by Chamonix's failure to publicly address this situation, a solution is really very simple. For existing fresnel-equipped 4x5 cameras, Chamonix needs to source integral acrylic focus screens, i.e. those with a frosted side facing the lens and fresnel rings facing the photographer (Maxwell, for example), and supply them to the cameras' owners along with clear cover glass for protection. Since the back's well is deep enough for ground glass plus fresnel, it's deep enough for such a combination. That would result in absolutely accurate focus and, at a cost to the manufacturer, quiet all complaints about design quality.

For future production of fresnel-equipped 4x5 cameras, Chamonix merely needs to mill its back wells deeper by 1/3 the thickness of a separate fresnel lens. Doing so will also provide absolutely accurate focus while enabling Chamonix to maintain its preferred supply source(s) for fresnels and ground glass, thereby maintaining attractive pricing going forward.


GPS, do you actually have a Chamonix, or are you just trying to stir up shit?I rarely comment directly about other participants here, but GPS has made many abrasive posts and seems to revel in promoting discord. My sincere suggestion is that GPS try more honey and less vinegar.

Bob Salomon
28-Oct-2009, 11:50
"Chamonix merely needs to mill its back wells deeper by 1/3 the thickness of a separate fresnel lens. "

But all fresnel screens are not the same thickness.
The problem is that you appear to be putting the fresnel in front of the ground glass. The real cure is to position the ground side of the gg at the film plane and then position the fresnel on top of the gg. That way the focusing part of the system is closest to the lens and always mounted on the lens side so the thickness of either the gg or the fresnel screen does not matter.

Sal Santamaura
28-Oct-2009, 12:03
"Chamonix merely needs to mill its back wells deeper by 1/3 the thickness of a separate fresnel lens. "

But all fresnel screens are not the same thickness...Yes, Bob, but Chamonix should know how thick the fresnel lens it uses is. :)


"...The problem is that you appear to be putting the fresnel in front of the ground glass. The real cure is to position the ground side of the gg at the film plane and then position the fresnel on top of the gg. That way the focusing part of the system is closest to the lens and always mounted on the lens side so the thickness of either the gg or the fresnel screen does not matter.However, taking that approach (which is what some in this thread have done) leaves the fresnel subject to scratching by loupes, etc. A clear cover glass would offer protection, but the Chamonix back's well isn't deep enough to accommodate three pieces.

shadowleaves
28-Oct-2009, 12:49
"Chamonix merely needs to mill its back wells deeper by 1/3 the thickness of a separate fresnel lens. "

But all fresnel screens are not the same thickness.
The problem is that you appear to be putting the fresnel in front of the ground glass. The real cure is to position the ground side of the gg at the film plane and then position the fresnel on top of the gg. That way the focusing part of the system is closest to the lens and always mounted on the lens side so the thickness of either the gg or the fresnel screen does not matter.

This fresnel issue has been a trouble for the field since very long time ago. It's not a trivial issue and unfortunately there isn't a perfect solution for it. Different manufacturers took different approach. The approach of placing the fresnel between the user and GG is taken by Ebony, Sinar, and a couple of other manufacturers. The drawback is that, even with a protective glass, the fresnel grooves that are facing towards the user still make the focusing not so pleasant, as the grooves are easily visible and disturbing. Maxwell screens boast finer grooves but that increase cost and, as I see it, the grooves are still clearly visible.

Another approach taken by Arca Swiss is to keep the fresnel between the GG and lense. According to my test, whether the grooves are facing the GG or lense does not matter. The focus shift is caused by the thickness of the fresnel, not by the grooves. In other word, even you replace the fresnel with a transparent acrylic board made with the same material and to the same thickness as the fresnel, you'll still see the focus shift. Arca Swiss (at least on the 171-110 Field model I have) therefore adjusts the ground glass position by 1/3 of the fresnel thickness by using shims. This way focusing shift is well corrected for most lense across the entire field, except for edge focusing with super-wide lense (<75mm on 4x5); and the fresnel grooves are not visible if you install it facing towards the lense. Chamonix took this approach, however they didn't use shims to adjust the focus shift. Thus we all saw the problem being discussed so far.

There could be also a third approach. LensN2shutter once boasted a super-thin 0.018" (0.46mm) fresnel design, and according to them the focusing shift is so small (around 0.15mm) that it won't affect most applications if the fresnel is placed between the GG and lense. To me this sounds reasonable, however LensN2shutter hasn't been replying emails for quite a while and I'm not sure if they're still in business. I've no idea about the cost of their fresnels.

If one only cares about focusing in the center of the frame, then he can certainly drill a hole in the center of the fresnel and place it between the GG and lense. Not sure if this constitutes the 4th solution.

Ulrich Drolshagen
28-Oct-2009, 13:39
Arca Swiss (at least on the 171-110 Field model I have) therefore adjusts the ground glass position by 1/3 of the fresnel thickness by using shims.

I am confused now. Must it be shimed (the focusing plane of the groundglass gets away from the fresnel, nearer to the viewing side so to say) or must the rebate the groundglass rests in be milled deeper (focusing plane nearer to the lens side) as some other poster suggested?

To my experience the direction of the grooves of the fresnel does not have any effect. I have found a solution attaching the fresnel on top of the groundglass with the grooves facing the groundglass.

I have just made a test to see what happens to the focus in about 2 1/3 ft distance. At least at this close distance, taken wide open with a f5.6/150mm lens, the effect seems to be smaller than a possible focusing mistake.

What happens at larger distances?

Ulrich

shadowleaves
28-Oct-2009, 14:16
the GG needs to get away from the lense. Arca Swiss shims both fresnel and GG so that they still touch each other, and the GG/fresnel moves away from the lense together, for 1/3 of the thickness of the fresnel.

If you put the fresnel on top of the GG, you won't have any focus shift. It's just that the fresnel grooves are a bit disturbing when focusing.



I am confused now. Must it be shimed (the focusing plane of the groundglass gets away from the fresnel, nearer to the viewing side so to say) or must the rebate the groundglass rests in be milled deeper (focusing plane nearer to the lens side) as some other poster suggested?

To my experience the direction of the grooves of the fresnel does not have any effect. I have found a solution attaching the fresnel on top of the groundglass with the grooves facing the groundglass.

I have just made a test to see what happens to the focus in about 2 1/3 ft distance. At least at this close distance, taken wide open with a f5.6/150mm lens, the effect seems to be smaller than a possible focusing mistake.

What happens at larger distances?

Ulrich

stealthman_1
2-Nov-2009, 22:32
I shot this tonight with a 45n-1 I took delivery of last Octoberish.
Turn of the Century Goerz Dagor 300mm f7.7 wide open on Delta 100.
General scene
http://farm3.static.flickr.com/2456/4071217614_330f5a9168.jpg
100% crop of an 800dpi scan with a V700. I'm struggling to see a focus issue...
http://farm3.static.flickr.com/2613/4071218068_f4118555d8_o.jpg

Ulrich Drolshagen
2-Nov-2009, 23:16
I shot this tonight with a 45n-1 I took delivery of last Octoberish.
Turn of the Century Goerz Dagor 300mm f7.7 wide open on Delta 100.
General scene
http://farm3.static.flickr.com/2456/4071217614_330f5a9168.jpg
100% crop of an 800dpi scan with a V700. I'm struggling to see a focus issue...

At what distance did you take the picture?

Ulrich

stealthman_1
2-Nov-2009, 23:30
5ft 10inch to the film plane.

Ulrich Drolshagen
3-Nov-2009, 03:46
I'll make a test at about 5 to 7 yards. I expect the effect to be the larger the greater the distance is. May be up to 3 yards it doesn't make a difference and about infinity it doesn't matter any more. May concern is with the distances in between.

Ulrich

rugenius
7-Nov-2009, 01:12
I realize this topic was beat to death...
But I've read through the posts and for the life of me I don't understand why it's a Chamonix specific problem.
Surely it makes sense that at some point, the Fresnel lens will interfere with the ability of the user to adjust the image-focus plane as seen through the ground glass to match the exact film plane.
IE: If the Fresnel lens is placed in front of the GG .
Granted, the benefit is to protect the brightening Fresnel lens element if you do...
This is how my camera was constructed when I purchased the used 045N a few months ago.

Note: It's a whole different ball game if we are talking about custom screens like Maxwell, etc,...

IMHO, Nothing is for free.

GPS
7-Nov-2009, 01:57
I realize this topic was beat to death...
But I've read through the posts and for the life of me I don't understand why it's a Chamonix specific problem.
...

Shadowleaves explained that quite clearly, see the post # 54.

rugenius
7-Nov-2009, 13:54
GPS: I get the post #54...

My point is,..
If the Fresnel is on the lens side between the GG...
You are ALWAYS making a compromise... however thin the Fresnel...
Especially in combination with short focal length wide angle optics.

The GG is supposed to define the film plane...
Any other position of the GG while involving a screen intensifier is a compromise.
Compensating for Fresnel thickness/effects require moving the GG position respective of the Camera back/ rear standard.

Chamonix doesn't tell us that we have to use the Fresnel, it's a viewing aid and has limitations like any.

GPS
7-Nov-2009, 14:10
GPS: I get the post #54...

My point is,..
...
Compensating for Fresnel thickness/effects require moving the GG position respective of the Camera back/ rear standard.

Chamonix doesn't tell us that we have to use the Fresnel, it's a viewing aid and has limitations like any.

Of course the compensating requires the GG position change, we all know it, that's the whole point. Chamonix didn't make that repositioning - the whole thread is about that.
And the Fresnell is on the camera in question - you have to use it unless you throw it away. What's so difficult to understand here?

stealthman_1
8-Nov-2009, 12:45
Having re-read both threads, I still don't get it. I've read about focus error in wide angle architectural shots, infinity shots, people are checking for less than infinity, but longer than 5 yards, and there seems to be a good dose of misunderstanding about what a view camera just plain does as a function of tilt and shift and starting at the GG when T/S variables haven't been eliminated is just a bad idea. A simple look at some DOF tables has stopped me from doing any further testing. I pulled out the 75 f6.8 Rodenstock and a Schneider/Sinar SA, 90mm, f5.6 to play with today, but once I confirmed what I should expect from DOF, I said why bother. At just five feet you've got over a foot of DOF and at 15 you have almost 23 feet with the Rodenstock, I don't need a ruler to evaluate focus error, it would be very obvious in the years worth of photos I've taken.
A fresnel screen increases brightness, that is its sole point and it is another lens inserted in the light path, but with any normal aperture (even wide open) found on any typical LF lens, DOF should minimize it ever affecting your photos. If you're shooting a larger than f4 aperture on the Chamonix, you don't need a fresnel and should understand it might cause you problems. That's on any field camera. If someone has a specific test I should do and will list the focal length (got 47mm to 600mm) and the distance the test should be carried out at, I'll have at it, but otherwise, this whole continued dialogue seems like user error or something else.

rugenius
8-Nov-2009, 13:32
GPS: We're both responding but don't seem to hear each other?:(

The whole thread started as a problem solving issue. Correct?

To that end,... I thought the gross erorr reported had more to do with the user than the Chamonix screen intensifier...

My concern was why people think Chamonix is to blame for a physics related phenomena related to the use of a Fresnel lens.:confused:

The "point of the thread" in your mind is the lack of positioning...:mad:

IMHO, articulating/moving the GG to compensate for an apparent focus through the Fresnel is bad optics engineering and invites more problems/ headaches if the non-expert users are allowed to play with it. The 1/3rd thickness rule is generalized at this point.
If Chamonix committed to resolving your problem via that method for all the variety of WA lenses,... it would invite more problems than it resolved.;)

A fixed GG plane is the correct method.
Assuming screen intensification is necessary,... imaging can be accomplished via ultra thin Fresnel to reduce the said effects, else place the intensifier between the person and the GG.... Else there are other brightening methods too.
There are other people in the forum that pointed out to simply remove the Fresnel, or use another screen intensifier, etc,...

Again,... While you can try to convince me the right thing to do is blame Chamonix for not providing a degree of freedom so that the user can move the optics to compensate for the Fresnel/ Fresnel thickness...I claim that's a bad engineering band aid and it will never satisfy the whole audience anyway.

So,... that's my point,... and I can definitely see the point of complaining to Chamonix that the setup is not optimized... but IMHO the solution is not as you proposed.

I appreciate the dialogue...
Cheers!

GPS
8-Nov-2009, 13:59
Indeed, somehow we don't understand each other.
Nobody wants Chamonix to "allow to play with it". Chamonix didn't do what any other manufacturer did - put the Fresnell combo to the right position right away. In that way the consumer has nothing to do.
I don't think somebody wanted to force Chamonix to allow customers themselves to do so on their cameras. You're still misunderstanding the thread, I'm afraid.

rugenius
8-Nov-2009, 20:17
GPS, my apologies for not taking the time understand all the details...
I purchased the camera second hand and thought the screen intensifier was an accessory/add-on for the Chamonix camera GG.

However, it was sold as part of the camera, integral to it and all specification.... and to this end I guess the Chamonix factory has admitted that the Fresnel location is a "design defect" and that it cannot be fixed,... emphasizing the whole point concerning the engineering shortcomings of placing the Fresnel between the GG and lens on ANY view camera.
http://www.chamonixviewcamera.com/Announcement.html

AlexGard
3-Jan-2015, 00:45
Hello. I'm here to dig up this thread.
I have a 045-f1. I do enjoy using it. However I have found focusing issues that I think are related to the Fresnel screen.
I have used in the past both a toyo field and sinar view camera as well as a tachi 8x10 without this issue.

Seems when I push my loupe against the protective screen, the image is in focus through the loupe, when I remove my loupe, the image on the GG does not appear in focus. Critical focusing is very frustrating and at shots where it matters, it seems that more often than not after development my negatives are out of focus, particularly with my 90mm lens (even when using smaller apertures)

This is on the F1 model, not N1 or N2.

I understand people are saying that the F1 saw this issue rectified, but I feel as if mine is still having a problem.

My main question here is, if I remove the Fresnel and just replace the plastic protective screen, will this affect my focusing? Or will it be true as the normal GG in the Chamonix? Or would it be best to leave the GG completely bare?

Anyone else with a F1 model have the problem?

Old-N-Feeble
3-Jan-2015, 11:18
I don't recall anyone complaining about the focus changing from using a loop to direct viewing. Does the focus change if you press on the screen with your finger? If so then perhaps the glass was replaced with plexiglass or some other type of plastic. Or perhaps the GG is loose. IIRC, the focus issue with the original model was caused by improper spacing of the GG due to the Fresnel.

I never even bothered looking at mine with the original panel setup. When I bought the camera I had it sent directly to the technician Bill Maxwell recommended to install the screen I bought from him.

AlexGard
3-Jan-2015, 16:10
The protective screen appears to be plexiglass, the Fresnel is, well a fresnell (kind of plastic) and the ground glass appears to be glass.

Old-N-Feeble
3-Jan-2015, 16:17
You're focusing through a cover intended to protect the glass from breakage during transport? That should be removed during use... it just slides out. How are you able to squeeze in the DDS with that in place?

Jac@stafford.net
3-Jan-2015, 16:43
My main question here is, if I remove the Fresnel and just replace the plastic protective screen, will this affect my focusing?

Throw that protective thing away and try again.

Timothy Blomquist
3-Jan-2015, 17:38
In 37 years of shooting large format, I have never used a Fresnel lens between the GG and lens. When I have used a Fresnel lens, it has been placed on the ground glass, and my focusing loupe makes contact with the smooth side of the Fresnel. Never had any issues with that set up and fine focus has been achieved. If you're using a ground glass protector (not a Fresnel), that is only on the camera for storage and transport.

Has anyone here had an issue with focus caused by the thickness of the Fresnel on the back (focusing loupe) side of the ground glass? I never have.

AlexGard
3-Jan-2015, 18:34
Thanks for the replies. I was not aware the Perspex screen was for protection during shipping only (seeing as it came with the carbon fibre plate over all the glass anyway)

and Old-n-feeble, what does DDS stand for?

Also, the Perspex cover did not just slide out, I had to unscrew the little plugs holding everything in to remove it.

cowanw
3-Jan-2015, 19:34
Even so, the perspex cover does not explain a difference in eyeball focusing and loupe focusing.

Old-N-Feeble
3-Jan-2015, 19:52
Thanks for the replies. I was not aware the Perspex screen was for protection during shipping only (seeing as it came with the carbon fibre plate over all the glass anyway)

and Old-n-feeble, what does DDS stand for?

Also, the Perspex cover did not just slide out, I had to unscrew the little plugs holding everything in to remove it.

That's not what I thought you were talking about. There are protective covers that just slide in like a film holder at front but cover the glass from the back. If you removed a permanent cover then it needs to go back in. A DDS is a Double Dark Slide.

Randy Moe
3-Jan-2015, 20:07
Just to add to the confusion, some of my Horseman have Fresnel between the GG and lens. And a couple have no Fresnel. And they use different GG attachments. None have Fresnel between GG and eyeballs, but my Sinar did and the Fresnel sure got beat up, but it was quick removable.

One of these days I will play bait and switch and see what is up.

This is on 2x3, 4x5 and 8x10 Horseman.

Most likely I am too blind to tell any difference or I stop down enough to cover it.

On my list of mysteries...





Big list.

Jac@stafford.net
4-Jan-2015, 08:03
[...]There are protective covers that just slide in like a film holder at front but cover the glass from the back.

Like this (http://www.digoliardi.net/groundglass-protector-main.jpg)? I cannot imagine a GG protector that could be in place when focusing. Can the OP post a snapshot of his?

Old-N-Feeble
4-Jan-2015, 09:58
Like this (http://www.digoliardi.net/groundglass-protector-main.jpg)? I cannot imagine a GG protector that could be in place when focusing. Can the OP post a snapshot of his?

Similar to that but made from clear plastic. I suppose I should have posted an image of one when I asked the question.

Something similar to THIS (http://mpex.com/canham-ground-glass-protector-4x10.html) is what I was asking about.