One shutter two lenses? (Aperture scale question)

[nathan.dana]

So I have a 90mm super angulon f8 that has a mediocre shutter (bulb doesn’t work), and a Rodenstock 135mm f5.6 with a good Copal 0 shutter. Any reason I can’t just mount the 90 in that shutter? How do I calculate the right aperture since the scale (I assume) will be off?


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[Bob Salomon]

One lens may or may not require shims. Aperture scales are available from lens manufactures. Since your shutter has a top and bottom scale you could get a set for the other lens and just replace the bottom scale.

Shutters are not designed for interchangeable cells and changing them can create problems:

1 you could loose the needed shims, if that lens needed them.
2 you could damage the threads on the cells or the shutter.

[nathan.dana]

Good idea on the second scale. What if neither has shims, and both screw in cleanly? Am I good to go then?


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[Leigh]

Hi Nathan,

The fact that a cell set does not require shims in one shutter tells you nothing about how it fits another shutter, unless the front-to-back thickness of the two shutters is identical.

- Leigh

[Luis-F-S]

If you ask me the idea is just dumb. I'd listen to what Bob S has to say above. Get a second shutter and have it properly mounted. Copal 0's are pretty cheap.

[rdenney]

I suspect the shims were there to accommodate variations in optical performance more than mechanical inconsistency. Manufacturing has tighter tolerances than the thickness of those shims.

The issue for me is dust getting into the shutter with frequent opening. But then convertible lenses often leave the shutter open, and have the same requirements for careful threading. But many lens cells leave the elements facing the shutter dangerously exposed, which will require hypercare.

Optical performance is easy to test, given that you have both lenses.

Rick “who has made his own aperture scales using very careful measurements with calipers” Denney

[Oslolens]

How do I calculate the right aperture since the scale (I assume) will be off?

Shutters have usually aperture scales on bottom and top. Use tape to fix a new scale at bottom. You can use a camera inside (dslr or analogue) to compare aperture between wide and normal, avoid calipers!

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[Bob Salomon]

Shutters have usually aperture scales on bottom and top. Use tape to fix a new scale at bottom. You can use a camera inside (dslr or analogue) to compare aperture between wide and normal, avoid calipers!

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See post 2!

[neil poulsen]

I toyed with this idea to switch between 90mm f5.6 and 90mm f8 sets of elements.

But since most of my architecture photos are exterior, I decided against the idea. (Don't really need the f5.6 elements.) And that's not to say that even these two sets of elements might not have differing shims.

But to do this for for different focal lengths just isn't worth the hassle. For example, the elements not mounted on the shutter would be exposed to scratches or damage.

[LabRat]

Adding to what Leigh said, at least use precision calipers to measure the distance between the front and rear outer rims when on the old shutter, and when on new to see if this measurement is exactly the same...

For me, I prefer the extra shutter (as mentioned) so at least one shutter works in the field if one fails, but the good thing about a new scale would be if one shutter conked out, you could swap the elements and keep shooting, so all lenses might have a cross scale is an idea...

Steve K