Fitting G-claron cells on a Copal shutter

[Luca Merlo]

I am very confused about mounting barrel lenses on shutters and the type of adjustments needed to the aperture scales. I own a Nikkor 150 W 5,6 and I am thinking about using the shutter of this lens with a G-Claron 150 barrel lens that I would like to buy. Shall in this case draw a new aperture scale or I just need to assemble the cells on the shutter ?

[Ernest Purdum]

Luca, you'e going without an answer for a long time so I'll toss in what I can. I was hoping somebody who had the Nikon would chime in so as to be sure which size shutter it has. At any rate, you can find out if it doessn't say right on the front. If it has the same size threads for the lens cells front and rear, it's a size 0, which is what is needed for the G-Claon 150.

You will need a new aperture scale. Take a look at the www.skgrimes.com website.

[Sal Santamaura]

I simply put 150mm Germinar W cells purchased from Kerry last year into the Copal No. 0 shutter of my 150mm Nikkor and placed a bit of black tape over scale markings from 5.6 to 8. Exposure accuracy is spot on. If the G-Claron threads are the same as those of my Germinar W, which they supposedly are, you're all set; no new scale needed. Screw them in and shoot! Just don't make any pictures thinking you've got an f/5.6 lens.

[ronald moravec]

You should measure the total length of the lens after installation to check that the cell spacing is correct. Some lenses use thin spacers to get it correct.

Of course you can could just try it. But if you start to get aberations at the edges, that is the problem.

[Luca Merlo]

Ernest, Ernest, Mr. Moravec, many thanks for your responses. I will let you know about the fitting.

[Frank Filippone]

When you get the new cel;ls into the shutter, you need to otremember only 1 item....there is no F5.6 on a G-Claron lens. The lens start at F9. All markings below F9 are "not supported". You do not need a new scale, all you need to do is to remember there is no F5.6, etc. Your widest lens opening is set by the lens itself and that is F9. Use a bit of tape to obscure the wider lens markings to be sure you do not forget. Note.. the lens markings are the same for all lenses with the same focal length.... all 150 lenses have the same aperture size requirements, thuis the markings oin the shutter are the same.

Frank

[Ernest Purdum]

I have to respectfully disagree with Sal Santamaura and Frank Filippone. All 150mm lenses will have the same aperure sizes only if the front cell has the same magnification of the diaphragm. It is not the actual aperture size which determines the f stop when divided into the focal length, it is the apparent aperture size. You can see the difference just by observing the diaphragm with and without the front cell in place. Mr. Santamaura has apparently lucked out in that the error in his instance is small, but that is not to be expected. You could try your present scale, but the chances are that you will encounter a troublesome error. Having a new scale made up is not all that expensive and could save you from improper exposures.

[Ernest Purdum]

I have to respectfully disagree with Sal Santamaura and Frank Filippone. All 150mm lenses will have the same aperure sizes only if the front cells have the same magnification of the diaphragm. It is not the actual aperture size which determines the f stop when divided into the focal length, it is the apparent aperture size. You can see the difference just by observing the diaphragm with and without the front cell in place. Mr. Santamaura has apparently lucked out in that the error in his instance is small, but that is not to be expected. You could try your present scale, but the chances are that you will encounter a troublesome error. Having a new scale made up is not all that expensive and could save you from improper exposures.

[Ole Tjugen]

I don't know the construction type of the 150W, except that it's very unlikely to be a Tessar. Since the Tessar is one of very few lens constructions in common use that diverges significantly from symmetrical, I would believe that the chances of getting a large error with simply using the same scale is insignificant.

Use your G-Claron in the shutter from the Nikkor, and be confident that the error in aperture opening will be less than the variation in shutter time between to subsequent exposures - and significantly smaller than the difference in effective shutter time with the same speed at different apertures.

I thought I wuold have to make a new scale for my G-Claron 355 which I was going to mount in the shutter from a 360mm Tele-Xenar, but then I sold the lens instead. Now I have to make a new scale for a shutter from a 210mm Xenar - which IS unsymmetrical.

[lee\c]

I would send the shutter to SK Grimes and have them engrave the shutter for the G Claron 150. I have a 150 and a 305 G Claron and that was an easy fix. I think I paid $45 for each shutter. took about a week. Second best $100 I ever spent.

lee\c