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
190879

At f22
190880

At f64
190881

At f280
190882

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.

[Bernice Loui]

Which is the reason re-mounting some of these lenses into a shutter is cost questionable. IMO, unless there is a dire reason to "re-mount" a given lens into a shutter, it is better to simply purchase a proven good lens in shutter. For those lenses in barrel that are a direct fit into shutter, the difficulty of applying the correct aperture scale to the shutter remains. All of this difficult and cost does not happen when the lens in shutter is purchased.


Bernice



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.

[swmcl]

Bernice,

I appreciate every comment.

1. At least one of us didn't know of such a thing until after the lens had been re-modelled into the shutter!
2. Grimes has marked the shutter as being from f10 to f128. I miss out on f9. The original went from f9 to f128.
3. I wish all shutters had these aperture mechanisms, just because they are so lovely...! It should also be said that the aperture numbers would need to reach 135 degrees around the barrel. 'Normal' apertures (the Copal #3) have a swing of around 75 degrees. This one has a swing of around 135 degrees. This would offer a greater precision in aperture setting for a purist - especially at the higher numbers. Then again, it really is completely unnecessary...
4. The cost was 575 US dollars to re-mount the lens and this particular one was won at auction for 100 US dollars because it had 'issues' that were resolved at Grimes. The total in this case, was less than or comparable to the Nikkor 450mm f9 lens which is the near-equivalent. It wasn't a completely 'to-the-hell-with-it' exercise. The normal cost would be 300 to 400 for the lens alone I think. Now the lens can come with me on a walk and it can see some pretty things and not be left all alone in a dark place...

Steve

[Bernice Loui]

Experience with lenses in barrel & shutter comes with tinkering with a LOT of them over a long period of time. There was a time in the not too distant past when Melles Griot sold new Ilex shutters and offered a lens to shutter service. This was before SK Grimes was doing the lens to shutter service. Melles Griot would install your lens cells into a new Ilex shutter, make a set of adapters, black anodize them and engrave the f-stops on the Ilex front plate. This service was not low cost (nearly $1K in early 1990's U$D) but acceptable for BIG lenses like a 35" Goerz Artar and such. Advantage to an Ilex over a Copal was a round Iris and they are reliable-accurate when new with the last versions being quite good.

https://www.melleroptics.com/?gclid=EAIaIQobChMIrPzMsYOC4gIVmbbACh3cZwLzEAAYASAAEgJdDfD_BwE


One risk of "re-modeling" barrel lenses into shutter is performance of the to be remodeled barrel lens. It is always prudent to test the lens to be remodeled as much as possible to assure it's performance is worthy to be remodeled as lens performance varies lens by individual lens with the brand and type not assurance of it's actual film burning performance. There is today LOTs of on-line rant-raves of a particular lens type and brand being fabulous and must own yet that might be a totally isolated example of that given lens. Many of the lenses today are decades old and used-cared for in often totally unknown ways which results in unpredictable optical performance until that specific lens is tested to prove it's actual optical performance.

Difference between f9 to f10 is a fraction of a f-stop which is just not that much in real world film burning. The iris shape might not be all that significant if the lens is stopped down past f22 for film burning. Iris shape matters more with larger apertures like f4.5 to say f11, maybe f16 on film sized of 4x5 and larger.


Most important, is to used your newly minted lens to burn film and make prints :)


Bernice

[mdarnton]

OP, if I am thinking correctly of your question, the "answer" is not that it is some sort of double-action mechanism, but that the contour of each aperture leaf changes along it's length so that the section that is in use at any moment is tangent to the aperture circle. On more simple lenses a regular curve accomplishes that, mostly, but when you are heading for very small stops, more complex leaf shapes are necessary. You can see these odd shapes if you look more closely at the individual leaves in the Apo-Ronar pix Bernice just posted.

[Alan Gales]

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


Go out like a rock star, huh?


https://www.theguardian.com/uk/2002/dec/12/arts.artsnews

[Dan Fromm]

Go out like a rock star, huh?


https://www.theguardian.com/uk/2002/dec/12/arts.artsnews

Not really. Between birth and death, which hasn't come yet, I've been ignorant and usually clothed.

[Alan Gales]

Not really. Between birth and death, which hasn't come yet, I've been ignorant and usually clothed.


Yeah, you are just like most of us. ;)