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View Full Version : Velostigmat series II 162mm - how to use it?



Patrik Roseen
8-Mar-2008, 10:35
Hello, I recently picked up a Wollensak Velostigmat series II f4.5/162mm in a shutter on ebay. This lens does not have the diffusion mechanism that can be found on the larger lenses, but the rear cell of the front element unscrews easily. I intend to use it on 4x5".

There are lots of threads about the common practice (or rather agreed confusion) how to use the larger lenses, but how should the smaller ones be used.

What I have found so far playing around with it is that if I increase the distance between the rear cell and front cell of the front element and then attach the front into the shutter w aperture wide open,
- the focal length will become shorter,
- the lens will not be as sharp when refocused,
- and the difference between focus and out of focus areas will become smaller when refocused.

Another thing I noticed is that it does not seem to matter (much) if I put the front element back completely or not, i.e. the position is negligable compared to the distance between the two cells in the front element itself.

When refocusing after diffusing, I seem to need some 2-3 turns to get a noticable effect, but overdoing it will cause ring and center effects in highlight areas. Since the procedure I am using is quite tedious I turn to the gurus on this forum for assistance in breaking in this lens...

Is there any common practice for using the Velostigmat without diffusion mechanism,in terms of:
- Do you diffuse first and then focus, or focus first and then diffuse?
- Depending on the first guestion, the necessary diffusion applied might have to be different. How much diffusion in terms of revelations of the rear cell is required to gain an effect or not?

I would be most grateful for any personal experience of this lens, especially if used for portraits.

Jon Wilson
8-Mar-2008, 13:16
In my experience, most of these Wolly lens did not have the diffuser ring. As with any lens, you can adjust the distance between cells by unscrewing them, which in turn will alter the image. You will just need to experiment with your new lens to see what you can get it to produce. BTW, I doubt this lens was actually intended for portrait work. It probably was designed as a "normal" length lens to use on a 4x5 camera. You will find that the wider aperature will decrease the depth of field as compared to the smaller aperature setting and thus this may create the "portrait" image you are looking to acheive. Best wishes, Jon

Dan Fromm
8-Mar-2008, 14:00
Patrick, the Velostigmat Ser. II is just another tessar. If you look at this http://www.cameraeccentric.com/html/info/wollensakcatg/p4.html catalog page you'll see that the little 'uns don't have the diffusing device.

By the way, the catalogs on that site aren't the last word. None lists a 3"/4.5 Velostigmat Ser. II but I have one.

Cheers,

Dan

Patrik Roseen
8-Mar-2008, 15:24
Dan and Jon, I already know this smaller lens does not have the diffusion device, i.e. the thing you turn from 0 to 5. But I was of the understanding that they were the same lens design and that the only difference with the ´device´is that one can expand the distance between the two cells within the front element without having to remove the front element etc.

I am just trying to accomplish the same thing ´manually´ and I think I understand how to do it.

Searching through the web I have seen the following practices for the diffusion but there are probably more.

1) Focus with 0 diffusion -> Apply diffusion --> choose f-stop.. expose

2) Focus with 0 diff -> apply f-stop till required DOF --> apply diffusion.. expose

3) Choose diffusion -> focus -> choose f-stop ..expose

The problem is of course that in my case I need to remove the front cell etc so procedure 3 would be the easiest as long as I could workout how many turns corresponds to minor, moderate and major diffusion.

Dan, are the larger Velostigmat of different lens design optically compared to the 162mm?

Dan Fromm
8-Mar-2008, 16:12
Patrik, I can't be absolutely sure but as far as I know all Velostigmat Ser. IIs are plain ordinary tessar types designed in Rochester.

cowanw
8-Mar-2008, 17:10
When I started with the diffused velo I focussed along a yardstick and it became apparent that the biggest effect was a simply a shift in the focus point. If you want to mimic this just misfocus.
I have come to the conclusion that your no.3 choice is the best.
Regards
Bill

Patrik Roseen
9-Mar-2008, 06:51
Thank you Bill, you might have found the answer... and Dan for pointing me in the direction of the Tessar design.

After playing around some more with this lens...
(until the rear cell element detached from the ring and I had to glue it back together again)
...I am more than eager to learn what the diffussion device is actually trying to accomplish on the larger lenses.

I have received some PMs explaning that it is
- increasing the distance between the front cell and the rear cell of the front element.
- and that the rear cell stays in position and the front cell moves forward.

I have also learned from reading the web that in a Tessar, that the rear cell of the front element is actually the center of the total lens, with a rather huge lens in front and a cemented doublet in the back.
The Tessar design is such that the major influence of the lens is in the front and that this is the reason why the distance between the center and the larger front cells can be increased without influencing the overall performance of the total lens and hence be used as a focusing device.

In my own experiments I have found that
- the Focal Length of the total lens decrease as the distance between the two elements in the front cell increase
...thereby making the lens focus on something more closeup than before given the same bellows draw.

Is this all that is to this 'device' and that is why it works for portraits where seldom something else will come in focus because there is nothing in front of the person being photographed.

Or is there something else introduced as the distance increase, e.g. abberation, coma, curvature,...

Any thoughts on what actually happens to the Tessar design while applying the 'diffusion device' would be much appreciated?

Peter K
9-Mar-2008, 07:37
When the negative meniscus in a Tessar-type lens is shifted, the focal length of the lens will change. This is the principle of a zoom lens.

But long time before the first real zoom lens this was used to change the spherical correction of a lens, e.g. the Universal-Heliar used this to get soft-focus images. Or the Velostigmat.

With a different focal-lenght also the aperture changes. So one has to correct this also. Of course this needs an effort in the mounting of a lens, so this was only done with more expensive long focal-lengt lenses.

Paul Fitzgerald
9-Mar-2008, 08:02
Patrik,

"In my own experiments I have found that
- the Focal Length of the total lens decrease as the distance between the two elements in the front cell increase
...thereby making the lens focus on something more closeup than before given the same bellows draw."

Exactly correct, that is how and why roll film folders with front element focusing work but they were never thought of as soft-focus.

Have fun with it.

cowanw
9-Mar-2008, 13:34
It would have been an excellent con job by the lens manufacturer if the only effect of the diffusion device was to cause a misfocus.
Once I get all my mounts done etc I plan a shoot off to compare images.
As Patrick says, Appreciate others experience and opinions please.
Regards
Bill

Peter K
9-Mar-2008, 14:12
Soft focus has nothing to do with misfocus.

Most softfocus lenses superimposes a sharp image with an image with spherical abberation. With the Velostigmat and the Universal Heliar the center lens can be shifted, the Imagon uses more or less parts of the outer part of the lens. Both system have their advantage, but the shortcoming of the shift system is focal-lengt shift and one has to refocus after alignment of the soft-focus device.

Peter K

Armin Seeholzer
10-Mar-2008, 07:16
Hi Peter
"Both system have their advantage, but the shortcoming of the shift system is focal-lengt shift and one has to refocus after alignment of the soft-focus device."

Its interessting what you say here I know I heard at least more often the oposite of this!
So what is really the trues about it!
Cheers Armin

Peter K
10-Mar-2008, 09:47
Armin,
you have both systems in your "dream lens" kit, the Imagon and the Universel-Heliar. So what is wrong about refocussing the Universal-Heliar? With the Imagon one can focus with closed sieves and adjust the softness without refocussing.

See also instructions fo a shift system http://www.cameraeccentric.com/html/info/graf/graf3.html
and for the Imagon
http://www.cameraeccentric.com/html/info/imagoncat/imagond.html

Peter K

Patrik Roseen
10-Mar-2008, 12:37
Soft focus has nothing to do with misfocus.

Most softfocus lenses superimposes a sharp image with an image with spherical abberation. With the Velostigmat and the Universal Heliar the center lens can be shifted, the Imagon uses more or less parts of the outer part of the lens. Both system have their advantage, but the shortcoming of the shift system is focal-lengt shift and one has to refocus after alignment of the soft-focus device.

Peter K

Thank you Peter for explaining how to use the diffusion device, i.e. to refocus after applying it.

Maybe the effect of the different diffusion mechanisms in terms of optical changes (sperical abberation, change in focal length etc) could be explained more thoroughly for different lens designs so that a lot of confusion about usage could be straightened out.

Peter K
10-Mar-2008, 12:59
Sometimes one can find correction curves in the patent literature. Or in the literature relevant to the subject. E.g. Rudolf Kingslake; A history of the photographic lens; Boston a.o. 1989 or W. Merté, R. Richter, M. v. Rohr; Das photographische Objektiv; Wien 1932.

But all this curves and numbers cannot describe the bokeh a certain lens together with a certain diffusion will make. So ask your lens and take photographs!

Peter K