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Thierry Schreiner
11-Mar-2007, 18:09
Hi to all,

I have a 360mm Imagon in a Compound 5 shutter lying around for quite some time and now want to start using it.

I guess I have read every possible thread concerning the use of Imagon lenses, but I must have missed something essential, or I am completely lost in outer space.

The lens has the 3 original disks :

H 5,8 – H 7,7
H 7,7 – H 9.5
H 9,5 – H 11.5

I am aware that we are talking here about H-stops, not F-stops. (whatever the H stands for)

1) My question, in terms of light measurement, what F-stops do the H-stops correspond to ?

2) In order to use the Imagon lens without any of the three disks, but using the diaphragm of the Compound shutter, it would be useful to calibrate the F-stops settings.

The maximum opening of the shutter being 64mm, according to the F/D rule, this would give us a maximum aperture of 5,6.

Am I right in applying the same rule to determine the respective F-stop ?

3) Let’s now come back to the 3 original disks :

H 5,8 (center disk and small disks open) – H 7,7 (only center disk open, opening 38 mm)
H 7,7 (center disk and small disks open) – H 9,5 (only center disk open, opening 31,5 mm)
H 9,5 (center disk and small disks open) – H 11.5 (only center disk open, opening 26 mm)

If I apply the same F/D rule to the 3 disks with only the center disk open, I would obtain the following F-stops :

360mm / 38mm = F-stop 9,47
360mm / 31.5mm = F-stop 11,43
360mm / 36mm = F-stop 13.85

The F-stop numbers have strange similarities again with the H-numbers.

Is this reasoning correct, or am I wrong ?

4) Does someone out there have for sale the book from Alfons Scholz on the Imagon lens ?

That’s it. Hope you could follow my reasoning.

Thierry

Armin Seeholzer
12-Mar-2007, 04:54
Hi Thierry

The H stands for the german word "Helligkeit" wich means brightness!
ANd it further explains: "Thus as a setting of H 5.8 the picture should be exposed as with a lens stopped down to f 5.8 Don't worry about this description; in exposure therms, H- values operate exactly like traditional f stops."
And you always should fokus with the aperture diapragms wich you are use for the shoot, but for fokusing you should always close the smaller holes!
And after fokusing you can open it again if you like it!
Hope it helps, Armin Seeholzer

Brian K
12-Mar-2007, 05:17
Armin, I have always focused using the actual disk I intended on shooting with, but I focused at whatever setting of the small holes that I was going to use for the image. Was that wrong? It is easier to focus with the smaller holes closed, but it also increases the apparent DOF and I assumed that was similar to focusing a lens at f16 then shooting at F8 which obviously is incorrect.

Ted Harris
12-Mar-2007, 06:19
According to Bob Salomon, and my experience, focusing at the taking aperture works best.

Emmanuel BIGLER
12-Mar-2007, 07:34
The maximum opening of the shutter being 64mm, according to the F/D rule, this would give us a maximum aperture of 5,6.

Am I right in applying the same rule to determine the respective F-stop ?

Yes, but the slight discrepancy your are observing between your calculation and what is engraved for the minimum H-stop with peripheral apertures closed might be explained by
- the fact that the actual focal lenght could differ from 360mm by a few percent,
- the fact that the Compound iris is probably not located where the special Imagon variable iris is located.

I have a shutterless Imagon, and one can say that this is a rare example where the iris diameter that you can measure on the iris is exactly the same to be used for the F/D computation.
The technical reason is that the F/D number has to be computed with the diameter of the entrance pupil i.e. the image of the iris as viewed from the entrance side. In the shutterless Imagon, the entrance pupil is the iris itself...
My understanding for the shutterred Imagon is that the special iris is still in frornt, but that the shutter iris is behind the lesn elements. Am-I right ?

But as mentioned, simply use the H-stop values as engraved, this should work.
The fact that Rodenstock mentions something different than F-stops is probably explained by the fact that the H-numbers cannot be used to compute regular Depth If Field values.

resummerfield
12-Mar-2007, 08:25
.....My understanding for the shutterred Imagon is that the special iris is still in frornt, but that the shutter iris is behind the lesn elements. Am-I right ?.......From the back to the front in my shuttered Imagon 300 is the Lens, the shutter iris, and finally the special iris. So both shutter iris and special iris are in front of the lens, but separated by several mm.

Armin Seeholzer
12-Mar-2007, 17:35
Hi
I just stated what Rodenstock has written in there explanation how to use the Imagon!

No rumors just what they stated and also worked fine for me!
You can focus with the small holes open but it is much more difficult, Rodenstock even stated thad it will give a tiny bit of focus shift but they say also the Imagon has enough DOF for compensating it!
Hope it helps, Armin Seeholzer

Thierry Schreiner
13-Mar-2007, 15:49
Hi to all,

Thank's a lot for your input and help.

It's good to know you're out there when advice is needed.

Thank's again and best regards.

Thierry

6-Apr-2012, 15:30

Louis Pacilla
6-Apr-2012, 15:54

Huh?

6-Apr-2012, 16:06
help m,e out i can't seem to upload an image thanks lee

BrianShaw
6-Apr-2012, 16:12
Try the icon (4th from right) that has the label "insert Image" when your pointer hovers over it.

Mark Sawyer
6-Apr-2012, 16:23
Regarding whether to focus with the little holes open or closed, think of it this way: the large central hole is a small aperture, which gives a sharper image on a soft lens. The little holes let a little softness back in to compliment that sharp dominant image. It's easier to get the correct focus without that softness overlaying the image, especially since that "softness" is actually other sharp versions of the same image focused on slightly different focal planes due to spherical aberration.

That's the theory. In practice, it doesn't really matter due to the Yogi Berra principle.

eddie
6-Apr-2012, 17:53
A 5 year Old thread. Wild seeing ted's post. Really snapped me back.

David Brunell
6-Apr-2012, 18:46
Yep, focus with the holes closed then open them up for desired softness after focus has been achieved.

Bob Salomon
6-Apr-2012, 19:35
Yep, focus with the holes closed then open them up for desired softness after focus has been achieved.

And that will create a focus shift. Always focus an Imagon under the same condition it will be used at. Easiest way to focus while learning the lens is to hold a high output halogen or LED flashlight at the base of the nose and focus on the lamp till you see a cross. When the cross appears you are in focus. Remove the light and study how the imah=ge is recorded to learn what an Imagon soft focus image looks like.

David Brunell
6-Apr-2012, 19:44
And that will create a focus shift. Always focus an Imagon under the same condition it will be used at. Easiest way to focus while learning the lens is to hold a high output halogen or LED flashlight at the base of the nose and focus on the lamp till you see a cross. When the cross appears you are in focus. Remove the light and study how the imah=ge is recorded to learn what an Imagon soft focus image looks like.

Thanks Bob, I must have mis-read the information or it was false. Anyway, I have just started to use the 250 and I am glad you pointed that out, it will save me some wasted film!

David Brunell
6-Apr-2012, 20:13
"Easiest way to focus while learning the lens is to hold a high output halogen or LED flashlight at the base of the nose and focus on the lamp till you see a cross. When the cross appears you are in focus."

By the way, thank you for that tutorial tip on how to focus; It will be used extensively this weekend.

Mark Sawyer
6-Apr-2012, 20:47
And that will create a focus shift. Always focus an Imagon under the same condition it will be used at. Easiest way to focus while learning the lens is to hold a high output halogen or LED flashlight at the base of the nose and focus on the lamp till you see a cross. When the cross appears you are in focus. Remove the light and study how the imah=ge is recorded to learn what an Imagon soft focus image looks like.

I'm going to have to disagree with Bob here. You have focused the main sharp image under the same condition it will be used at with the holes closed. Adding focus shift afterwards from the little holes being opened is what you want, because they're supposed to be focused off the sharp focal plane due to spherical aberration. That's what makes a soft focus lens work.

Shen45
6-Apr-2012, 21:16
Has anyone used an Imagon with just a shutter iris control for aperture? What type of soft focus lens is it compared to the Imagon using the discs. Eg H5.8 compared to f5.8 . Would the Imagon behave something like a Portland or the Kodak portrait lens that has the iris in front of the lens? I understand it was designed for the use with a disc in place ---- but??

Mark Sawyer
6-Apr-2012, 21:36
I've used it both ways, and it's nice both ways. The softness from the little holes is subtle, even with the 5.8/7.7 disc with the little holes open. I like it best with just a touch of the conventional iris closed. It's also nice wide open, but very soft.

Armin Seeholzer
7-Apr-2012, 07:21
I've used it both ways, and it's nice both ways. The softness from the little holes is subtle, even with the 5.8/7.7 disc with the little holes open. I like it best with just a touch of the conventional iris closed. It's also nice wide open, but very soft.

Same here in Switzerland to!
Bob want they do it the hard way, which is really not needed, I just revered to what standing in my german booklet to the lens! And I read better german then writing in english;--))) Bob is revering to older written user guides which I also know, but which are deadly unpractically! But if someone like it the hard way, just do it!

Cheers Armin

Old-N-Feeble
7-Apr-2012, 07:53
I've never like the effect of the "little holes" on the disks. I DO like the overall effect, in the right context, as controlled by the center holes of the discs. I truly HATE what the little holes do to bright highlights.

7-Apr-2012, 08:43
71513 200mm imagon no strainers f/8

David Brunell
7-Apr-2012, 09:25
71513 200mm imagon no strainers f/8

Nice Lee, do you have any more examples with this lens?

By "no strainers f/8" do you mean you closed the iris down to that f stop? or Did you use the disk with the strainers closed?

7-Apr-2012, 12:44
f/8 with iris no disks

David Brunell
7-Apr-2012, 12:46
Intersting, how did you determine it was f/8? I have a copal #3 and it is unmarked.

7-Apr-2012, 12:56
71535 i measured the diameter of lens divided into focal length. around f/8 with diffuser disk

Mark Sawyer
7-Apr-2012, 13:49
Okay, I was curious, so went to Seth's site and read Heinrich Kuhn's booklet on the Imagon. (Kuhn designed the Imagon, so I figured he'd know...)

http://cameraeccentric.com/html/info/imagon_2.html

Middle of page 4: "The following may be helpful to simplify correct focussing on the ground glass: with the small holes of the rotary diagram totally closed, thereby using only the central rays, not the slightest difficulty in focussing should be experienced..." He goes on from there for a while in more detail.

eddie
8-Apr-2012, 06:52
Intersting, how did you determine it was f/8? I have a copal #3 and it is unmarked.

measure the iris opening and divide......

easiest to use a metric measuring device to measure the opening. 250mm lens. 31.25mm opening. = f8.

Mark Sawyer
8-Apr-2012, 11:55
measure the iris opening and divide......

easiest to use a metric measuring device to measure the opening. 250mm lens. 31.25mm opening. = f8.

I've wondered if this is why American and British lenses were often marked in metric rather than or along with inches, even before metric started taking over: to get rid of those pesky fractions-of-an-inch when dividing...

cowanw
8-Apr-2012, 12:12
I'm going to have to disagree with Bob here. You have focused the main sharp image under the same condition it will be used at with the holes closed. Adding focus shift afterwards from the little holes being opened is what you want, because they're supposed to be focused off the sharp focal plane due to spherical aberration. That's what makes a soft focus lens work.

There is a range of choices with regards to best focus and we are looking at the opposite of the usual problem with smaller formats of focussing wide open and then stopping down. Mark suggests we focus stopped down and then open up the aperture (by opening the disc holes) to a larger f stop. Sort of the equivalent of focusing a Verito at f8 and then opening to f5.6 to shoot.
It is helpful to me to try to understand the ray diagram on this site.71597
http://toothwalker.org/optics/spherical.html
If I have it right, Mark is suggesting we focus at point C and Bob is suggesting point B.
It is also important to realize that focus shift moves closer with a larger f stop. As applied to a portrait when we open the peripheral circles and keep the focus of the centre disc, the nose may become sharper but the eyes will still be in the attractive (behind the focus point) part of the DOF. ( the Graf Variable and the Cooke RVP are the opposite of this.)

Armin Seeholzer
8-Apr-2012, 15:20
The Imagon was in the early days also called "Tiefenbildner" in german because of the enormous DOF which it creates even at H 5,8 it gives a very long DOF which is usefully sharp!

Cheers Armin

Mark Sawyer
8-Apr-2012, 16:50
...Mark suggests we focus stopped down and then open up the aperture (by opening the disc holes) to a larger f stop. Sort of the equivalent of focusing a Verito at f8 and then opening to f5.6 to shoot.

Not the equivalent, because in the Verito, changing the aperture changes the depth of field significantly, which may cause you to miss the point of critical focus. Also, with more of the periphery of the lens making the Verito's image, it is a significant part of the overall focusing. I always focus the Verito at the taking aperture.

The little holes in the Imagon aperture are a small part of the overall exposure, meant as a soft overlay over the sharp image from the main aperture hole. Focus using that sharp image, which is the taking aperture as far as the sharp focus is concerned, then open the outer holes to overlay the soft image, (actually a sharp image, but on other focal planes).

But in practice, it doesn't make much difference...

Bob Salomon
9-Apr-2012, 09:03

"OPTICAL FEATURES OF THE IMAGON
The Imagon is a single-component cemented doublet with adequate corrections of all aberrations other then spherical. A special feature of this aberration is that it does not adequately define the focal length of the lens, for marginal rays meet in a different plane from central rays. The degree of this spherical aberration depends on the aperture. At large apertures it almost completely blurs the image but progressively disappears on stopping down. At the same time the plane of sharpest focus shifts. The object on which a lens with spherical aberration is focused at full aperture is no longer in the plane of sharpest focus of the stopped-down lens. HENCE THE RODENSTOCK IMAGON MUST ALWAYS BE FOCUSED AT THE APERTURE AT WHICH IT IS TO BE USED.

TAKING TECHNIQUES
....Due to its special characteristics THE IMAGON HAS TO BE FOCUSED AT THE APERTURE AT WHICH YOU INTEND TO EXPOSE THE PICTURE.

Always determine the zone of relative sharpness with the marginal diaphragm apertures fully closed. With the perforated daiphragm open, the ground glass screen image is too vague and gives you little idea of the detail rendering. Although opening the marginal apertures slightly alters the focal length, this is negligible. Forget about the complicated instructions for soft focus lenses found in older textbooks."

Mark Sawyer
9-Apr-2012, 18:52
And this is what the designer of the Imagon originally said:

"The following may be helpful to simplify correct focussing on the ground glass: with the small holes of the rotary diagram totally closed, thereby using only the central rays, not the slightest difficulty in focussing should be experienced..."

Closed makes more sense for precise focusing, open for seeing the soft effect. Doesn't matter too much either way, though...

Armin Seeholzer
10-Apr-2012, 06:08
Bob even if you put it in ultra large and red letters it get not more true! Mark and I also using it at the main aperture but we do then sometimes open up the small holes and this gives no shift in the center at all.
But anyway I use it most of the times without the discs anyway, which may kill the Imagon look but gives a normal SF look. And I know I do not have the permission from Rodenstock, but it does'nt matter anyway;--))))
And yes for all which like it complicated do it like Bob is pushing!

Cheers Armin

cowanw
10-Apr-2012, 07:36
Always determine the zone of relative sharpness with the marginal diaphragm apertures fully closed. With the perforated daiphragm open, the ground glass screen image is too vague and gives you little idea of the detail rendering. Although opening the marginal apertures slightly alters the focal length, this is negligible. Forget about the complicated instructions for soft focus lenses found in older textbooks."

"The following may be helpful to simplify correct focussing on the ground glass: with the small holes of the rotary diagram totally closed, thereby using only the central rays, not the slightest difficulty in focussing should be experienced..."

I think we are all saying the same thing.

"Bob even if you put it in ultra large and red letters it get not more true! Mark and I also using it at the main aperture but we do then sometimes open up the small holes and this gives no shift in the center at all.
But anyway I use it most of the times without the discs anyway, which may kill the Imagon look but gives a normal SF look. And I know I do not have the permission from Rodenstock, but it does'nt matter anyway;--))))
And yes for all which like it complicated do it like Bob is pushing!"

You make it sound combative. I for one am delighted when an industry rep participates in the forum.
All in all, someone needs to shoot a ruler open and shut and settle the issue.
A lens align
http://michaeltapesdesign.com/
would be perfect for this.

Bob Salomon
10-Apr-2012, 08:35
"The following may be helpful to simplify correct focussing on the ground glass: with the small holes of the rotary diagram totally closed, thereby using only the central rays, not the slightest difficulty in focussing should be experienced..."

I think we are all saying the same thing.

No, we are not. What I stated from the passages in the instruction book was that there IS a focus shift when you change the setting of the small openings. So if you focus with them closed and shoot with them open you have created a focus shift.

Mark Sawyer
10-Apr-2012, 10:05
I for one respect Bob's position, and am very glad he's here! He knows what he's talking about and has corrected me in the past, for which I'm grateful. I learned something!

Either way of focusing is fine, and both have been recommended by higher authorities than either of us, (Rodenstock, the manufacturer, and Kuhn, the designer).

To Bob's latest point, I agree, when you open the little holes, you allow a focus shift effect to be added over the sharper image. That focus shift from the outer portions of the lens is the "Imagon Effect", and if you don't want that to throw off your focusing on the main, sharp image from the central opening, you should close the holes. And if you could correct for all focus shift in focusing, you'd lose the "Imagon Effect". Soft focus depends on there being a zonal focus shift (spherical aberration) across the lens area.

An advantage to Bob's "open hole" method is that you can see the softness as you focus.

But we're just arguing theory, and Yogi Berra was right: "In theory, practice and theory are the same thing. In practice, they're not." In practice, I've focused the lens both ways, and it's fine either way. And the Imagon is a lovely lens. Cheers, Bob!

Antonio Scorletti
18-Jan-2014, 10:38
I've done a test shooting at different Helligkeit (H) with holes opened and closed. After printing (34x30 cm) the various (7) negatives (4x5) these are the things I've learned.
1.The extended DOF ( for which the name Tiefenbilder given) is true and I've understand this is due to the various plane of focus caused by spherical aberration. I focused the small brick on the fountain and the black wheel of the barrow has crisp contour! (See the only photo attached).
2. There is a difference between the flou effect depending on the H used, but the true determining factor to use this lens is the appropriate choice of the light: a scene with high light zones is the ideal.
Best
Antonio108706

Bill_1856
18-Jan-2014, 11:14
I'd just like to point out that the image from an Imagon doesn't look the same as an image from a "true" soft-focus lens such as the Veritar. It is unique (and personally, I don't care for it).

lenser
18-Jan-2014, 16:41
You should be able to find the complete user's manual at either www.cameraeccentric.com or at Butkus.org.

Antonio Scorletti
19-Jan-2014, 03:00
Hi Bill_1856,
Why Imagon is not a true soft focus lens?
Antonio

jp
19-Jan-2014, 05:54
Imagon is a true soft focus lens, plus a totally optional strainer.

Mark Sawyer
19-Jan-2014, 12:44
Imagon is a true soft focus lens, plus a totally optional strainer.

Agreed, and one of my favorites.

russyoung
7-Mar-2014, 19:18
As I read Kuhn's own words, the perforated diaphragm MUST be used: http://cameraeccentric.com/html/info/imagon_2.html

Russ

Tin Can
7-Mar-2014, 20:35
Ok that does it. My next lens will be a 480 Imagon, if I can ever find one again.

But for now it's my Mamiya RB 150mm SF Imaton (imitation).

Amedeus
8-Mar-2014, 10:33
I've heard the argument before the Imagon and the Fuji SF, another "strainer" soft focus lens not to be "real" soft focus lenses because of the need of a strainer to achieve a soft focus effect. From my perspective, it is just one of the multiple optical ways you can achieve a soft focus effect with, so it qualifies as a soft focus lens.

One may not like the bokeh of when shooting bright highlights as these takes the shape of the strainer but that's just a side effect ... not a reason to disqualify.

YMMV

Bernice Loui
8-Mar-2014, 10:46
Aka, Imagon "bugs"

Bernice

One may not like the bokeh of when shooting bright highlights as these takes the shape of the strainer but that's just a side effect ... not a reason to disqualify.

YMMV

Bob Salomon
8-Mar-2014, 14:45
I've heard the argument before the Imagon and the Fuji SF, another "strainer" soft focus lens not to be "real" soft focus lenses because of the need of a strainer to achieve a soft focus effect. From my perspective, it is just one of the multiple optical ways you can achieve a soft focus effect with, so it qualifies as a soft focus lens.

One may not like the bokeh of when shooting bright highlights as these takes the shape of the strainer but that's just a side effect ... not a reason to disqualify.

YMMV

That argument is false. The Imagon's softest setting is to use it with no disk. Then it is a 5.8 soft focus lens. Using the disks lets the user control the amount of softness and the degree of halation desired. And without the disk, wide open, there are no strainer effects.

Bernice Loui
8-Mar-2014, 16:28
+1

Softest setting on the Imagon is no disc, next softest would be H5.8 disc holes open and the holes can be partly closed to vary the degree of softness. This is the bits of info that makes using the Imagon less than simple.

Bernice

That argument is false. The Imagon's softest setting is to use it with no disk. Then it is a 5.8 soft focus lens. Using the disks lets the user control the amount of softness and the degree of halation desired. And without the disk, wide open, there are no strainer effects.

Mark Sawyer
8-Mar-2014, 18:14
111767
+1

Softest setting on the Imagon is no disc, next softest would be H5.8 disc holes open and the holes can be partly closed to vary the degree of softness...

+2

The Imagon discs are a second option in using the lens. It also works as a fine soft focus with a conventional aperture, which is why the designers went to quite a bit of trouble making discs where you can close the little holes and have a conventional aperture. I prefer to use mine with a conventional aperture, but the discs are nice too. Perhaps the Imagon offers too many options for the casual user to understand and get the most out of, but options are options, and one has the option of simply putting those discs away.

BTW, the discs are similar in design and use to the Verito Diffusion Stops:

http://i55.photobucket.com/albums/g139/Owen21k/veritoa.jpg (http://s55.photobucket.com/user/Owen21k/media/veritoa.jpg.html)

Tin Can
8-Mar-2014, 18:37
Finally reread my 1959 'Linhof Practice' book. Here is the book cover, two paragraphs on the Imagon and two full page example photos printed in the book of good uses of an Imagon. Originals about 8x10".

Sorry about the snapshots, but this P&S Nikon makes this stuff fast and easy handheld in low light.

111768111769111770111771

pierre506
8-Mar-2014, 19:59
Interesting~
I tried Imagon 300mm wide open yesterday.
Fuji 100C
Sorry for the bad image quality of cellphone.
111773

Steven Tribe
9-Mar-2014, 04:46
Control/limitation of the soft effect of the Imagon discs was adopted by "DIY"ers long ago. About 5 years ago, a Plasticca was sold in Stockholm with a complete set of period home-made imagon-type discs.

Bob Salomon
9-Mar-2014, 04:49
111767

+2

The Imagon discs are a second option in using the lens. It also works as a fine soft focus with a conventional aperture, which is why the designers went to quite a bit of trouble making discs where you can close the little holes and have a conventional aperture. I prefer to use mine with a conventional aperture, but the discs are nice too. Perhaps the Imagon offers too many options for the casual user to understand and get the most out of, but options are options, and one has the option of simply putting those discs away.

BTW, the discs are similar in design and use to the Verito Diffusion Stops:

http://i55.photobucket.com/albums/g139/Owen21k/veritoa.jpg (http://s55.photobucket.com/user/Owen21k/media/veritoa.jpg.html)

Raodenstock instructions specifically state that the aperture is not to be used as it changes how the peripheral rays are used and this destroys the Imagon to control disks let the user use a seleted amount of the peripheral rays to accurately control the halation effect the lens is famous for.

Mark Sawyer
9-Mar-2014, 15:10
Raodenstock instructions specifically state that the aperture is not to be used...

And General Motors specifically states the Corvette is not to be driven over the posted speed limit. :rolleyes:

We've had this argument before, Bob. All I can say from personal experience is that the Imagon is a fine lens whether you use the discs or a conventional aperture. I tend to prefer the conventional aperture. (But why did they make the discs with holes you can close if you're not supposed to close them?)