Graf Variable Anastigmat - Aperture Setting

**Flauvius** · 2-Jun-2007, 20:37

Hello Lens Experts:

I would appreciate your help in evaluating this strange lens.

Given that the Graf Variable Anastigmat 12.5-14 inch f/4.5 lens "apparently" does not have an iris, how does one set the aperture on this lens? Also, what is the purpose of the "long" set-screw that is positioned perpendicular to the knurled aperture ring with its dual "soft" and "sharp" f/stops?

The front element of this lens unscrews - like a helical mount. However, with only one aperture scale, but with "sharp" and "soft" f-stops on the outside of its aperture scale, how does does one engage the respective "sharp" and "soft" characteristics of this lens?

Lastly, for what applications was this lens originally intended.

Regards,

Flauvius

**Ernest Purdum** · 3-Jun-2007, 06:21

You've got me considerably confused. I'm not sure what you mean by the lens "apparently" not having a diaphragm. The Variables that I have had or have seen do have normal iris diaphragms which are used in the normal manner.

The movement of the front cell introduces spherical aberration when turned in the "soft" direction, giving an overall soft definition. This effect is strongest at wide aperture. At small stops the image will be pretty sharp regardless of the front cell setting.

The intent of the Variable was that it should be a versatile lens, capable of sharp definition or the amount of softness the photographer desired. At the time, it was used for a wide variety of work. Today, most people would use it only for subjects where some diffusion is desired.

If I haven't understood the question, please clarify.

**Flauvius** · 3-Jun-2007, 08:55

Ernest, perhaps I can best answer your question by means of a follow-up question of my own.

Initially, do you know the purpose of the 15mm set screw which is located in the knurled aperture ring? If so, what is the relationship of the "arrows" on the barrel to the aperture ring and the "slot" that the threaded aperture ring covers?

I suspect that the set screw engages the aperture ring with the shutter, but the lens does not seem to have an iris. However, given the lens is in its f/4.5 position, this apparent lack of an iris may be a function of the iris needing to be engaged by means of the set screw connecting the aperture right with the shutter.

Regards,

Flauvius

**Flauvius** · 3-Jun-2007, 09:19

Updated Post:

I just determined that the set screw connects the aperture ring to the iris, and that someone had incorrectly inserted the set screw. However, I still am at a loss as to the purpose of the arrows on the barrel and the set of two aperture settings, but with one complete and one parcel f/stop scale on a portion of the aperture ring.

Flauvius

**Ernest Purdum** · 3-Jun-2007, 10:01

The complete f stop scale is used in the normal manner. The markings on the soft/sharp adjustment are just to let you know how the focal length and the maximum aperture change as the amount of diffusion is selected.

If you do a search under "Graf", you will find more information about these lenses, including a reproduction instruction pamphlet kindly provided by Hans Visser.

**JasonC** · 4-Jun-2007, 06:43

Perhaps this manual will help.

http://www.cameraeccentric.com/html/info/graf/graf.html

As I understand it, the arrows on the barrel are completely arbitrary. They are there to help you remember how many turns till your favourite length setting.

Jason.