Shutter aperture mechanisms

[swmcl]

Hi,

I recently had a Nikkor 480 APO lens grafted onto a Copal #3 shutter by the Grimes factory. The bits were returned to me after the removal of the needed parts. I notice the mechanism for the aperture is a double-action aperture of some type. I think it is designed to extend the range of the aperture - meaning it goes from a large hole to a tiny hole. Does anyone know what that is called or where they might be found?

I will say it is a sexy piece of kit. I could sit in my lounge chair and just twiddle the aperture for hours!!

(probably a Dan Fromm question ...)

Cheers,
Steve

[Dan Fromm]

Steve, it is a mystery to me too.

When I was very young I wanted to know everything. At the age of twelve I measured everything and realized that I wouldn't live long enough to learn even a small fraction of everything. I then looked into learning only what was important, and discovered that I couldn't possibly learn enough to know what was important. Sigh.

Sorry,

Dan <born naked and ignorant, probably going to die naked and ignorant> Fromm

[swmcl]

:-)

[Bernice Loui]

Brass barrel APO Ronars have a aperture mechanism very similar to this which goes to f128 on some versions. They are a compound aperture leaf mechanism. Angeniuex zoom lenses have a mechanism like this too, but does not stop down nearly as far. The shape of the small stops on these apertures appear to have something to do with diffraction and how that reality of Nature_Physics interacts with those small apertures.

BTW, this is one of the perks that is given up once these lenses are installed into a shutter.


Bernice

Hi,

I recently had a Nikkor 480 APO lens grafted onto a Copal #3 shutter by the Grimes factory. The bits were returned to me after the removal of the needed parts. I notice the mechanism for the aperture is a double-action aperture of some type. I think it is designed to extend the range of the aperture - meaning it goes from a large hole to a tiny hole. Does anyone know what that is called or where they might be found?

I will say it is a sexy piece of kit. I could sit in my lounge chair and just twiddle the aperture for hours!!

(probably a Dan Fromm question ...)

Cheers,
Steve

[LabRat]

My boss (who is a big vintage audio collector) couldn't put down a barrel from a very large Tessar iris assy I was rebuilding, when he played with the iris for 10 or 15 minutes, like a cat studying a laser spot... He was amazed how round it stayed at all settings...

He in the past asked me why I bother with film, when there's digital, but after seeing the beauty of old camera tech, he doesn't bother me anymore about it... :-)

Steve K

[ic-racer]

Pictures???

[swmcl]

Labrat I like that story. It makes sense. Some things are attractive because of the design and workmanship and it is self-explanatory.

Picture is from an old digital camera - please excuse !

[Dan Fromm]

Oh, and by the way, at least come Kodak Cine Ektars also have, um, double irises.

[Bernice Loui]

19" Rodenstock APO Ronar in brass barrel has a nice round compound iris.

At f11


At f22


At f64


At f280


Opposite to the white aperture number engraving is the diameter of the iris in mm using red engraved numbers.
Notice the aperture spacing between f9 to f45 is wider to ease setting to fractional increments of f-stops.

On Goerz APO Artar, they achieve a nice round iris without a compound iris. Can illustrate this later with pictures.

Often not appreciated how remarkable the design of these iris are.
There are benefits to having a nice round iris like this which is given up once these barrel lenses are "re-mounted" into a Copal or similar modern shutter.

IMO, the better solution is to use these barrel lenses as is with an external shutter as they were originally intended. Having been down the "re-mount" barrel lenses into shutter decades ago, IMO it is simply not worth the cost and trade-offs.


Bernice

[Dan Fromm]

Bernice, some, not all, Apo-Ronars have cells that are direct fits in standard shutters. The same is true of most if not all G-Clarons. When no adapters are needed the cost of remounting the cells in shutter is just the cost of the shutter.

I have a small pile of process lenses and others (three f/14 Perigraphes, in particular) that I hang in front of shutters. The economics of doing this are horrendous unless, as miraculously is the case for me, a single lens-to-shutter adapter will serve several lenses. Very often shutter plus adapter(s) (for front mounting or to hold cells in the shutter and the right distance apart) cost more than a functionally equivalent lens already in shutter.