shutter compatibility question

[h2oman]

I just came to the realization that a given shutter, say a Copal 0, comes with a variety of aperture ranges. For example, one might have f6.8-f45, whereas another might have f9-f90. My questions are

a) can these be used interchangeably - in other words, can a f6.8-f45 shutter be used with lens cells that normally take an f9-f90 shutter

b) if the anser to (a) is yes, does, for example f16 with one shutter correspond to f16 with another on the same lens, or will the scale be off due to one f-stop on a particular lens having a particular physical aperture size from the same f-stop on a different lens.

I'm asking these questions because I want to replace a non-working shutter from one lens with a different (in the sense described above, but both Copal 1) shutter "robbed" from another lens. I'm also looking at possibly replacing a Copal 0 that is f9-f90 with another that is f9-f64.

Thanks for any help you can give me in this regard.

[IanG]

The shutters are identical the scales can usually be swapped but you need to know what you are doing. You need the right scale for the focal length.

Ian

[AJ Edmondson]

What IanG said... the aperture scale will depend on the focal length. As an example - a 360mm f9 lens mounted in a shutter set-up for a 180mm f4.5 would indicate f4.5 though it is actually f9. (180 / 4.5 =40 ; 360 / 9 =40) Focal length divided by aperture yields the opening.

Joel

[IanG]

I do use lenses in shutters with the wrong scale usually temporarily, and like Joel it's tended to be a simple re-calculation. I'd make a new scale if it was to be a permanent thing.

Ian

[h2oman]

Thanks guys, that helps. I might PM either of you if I have more questions.

Gregg

[AtlantaTerry]

Creating a new custom scale for a lens + shutter combo is what firms like SK Grimes do for a living, along with other work.

[Paul Ewins]

If you still have the broken shutter it is simple enough to make a temporary scale. Stick a piece of paper over the scale on the replacement shutter (a self adhesive address label is ideal) and trim to fit. Remove the cells from the faulty shutter and put them aside for the moment. Open the aperture on the faulty shutter to the widest stop on the scale (which is not necessarily as wide as it will go) and then measure the physical aperture. Now open up the aperture on the replacement shutter until it matches the measurement and then mark it accordingly on the paper scale. Repeat for as many of the other marked apertures that you can measure. Now screw the cells from the faulty shutter into the replacement. Job done.

Obviously a custom replacement scale from SKG will be nicer and the accuracy of the paper scale will be decided by your choice of measuring device but it beats trying to remember a conversion for any existing scale.

[AJ Edmondson]

Don't hesitate to do so Gregg. While SK Grimes does indeed make scales, they are not the only solution and there are other alternatives which are less expensive, don't require you to send your lens/shutter off and are equally efficient! Don't get me wrong - I have had work done by SKG (before his demise) and it is/was top-notch... just not the only viable option. (This is not a reflection on Adam's competence.)

Joel

[Cor]

This is how I approached it:
Mount a reference lens/shutter combination (obviously with the correct aperture scale) on your camera.
Focus at infinity (some distant feature >30* focal length).
Point the camera towards an EVENLY lit surface
Mount a spotmeter in such a way that the measuring part touches the same spot on the ground glass
Shield the spotmeter and ground glass from in-falling light (a dark cloth is perfect)
Measure light (I like EV values for that) at all the appropriate stops of your reference lens/shutter
Now mount your lens and the shutter without a correct aperture scale, focus on infinity, and move to exactly same evenly lit area.
Move the aperture level to obtain the EV values you found previously.
Mark these positions on your new scale (a piece of paper or something like that)
Done

best,

Cor

[h2oman]

Thanks, Cor - that makes sense.