# Thread: help! How do I calculate f-stop scale on a copal 0 shutter

1. ## help! How do I calculate f-stop scale on a copal 0 shutter

Can anyone explain the formula for calculating and calibrating a shutter. The copal 0 shutter on my schneider 72mm xl is dead and beyond repair, i have copal 0 on my 90mm nikon SW, and so will try and use it between the two lenses on my shoot tomorrow/this weekend. I'd like to calculate a temporary scale for when i use this shutter on the 72mmxl temporarally....

Also does anyone have a copal zero with reliable shutter speeds for sale!

thanks

Dan

2. ## Re: help! How do I calculate f-stop scale on a copal 0 shutter

You can make a temporary aperture scale for your shutter by copying the markings on the failed shutter's scale to a piece of tape and placing it on the good shutter.

3. ## Re: help! How do I calculate f-stop scale on a copal 0 shutter

Hello Dan,

I have an almost new Copal No. 0 shutter (the small one). This shutter came with a lens that was set as a DB lens on my Sinar. I've never used it. Contact me off list and we can discuss it.

4. ## Re: help! How do I calculate f-stop scale on a copal 0 shutter

Let me know when you replace your shutter. I hav need of some Copal 0 parts.

5. ## Re: help! How do I calculate f-stop scale on a copal 0 shutter

Why not transfer the scale from the broken one to its replacement?

They're just held on by two screws.

- Leigh

6. ## Re: help! How do I calculate f-stop scale on a copal 0 shutter

Originally Posted by Mark Stahlke
You can make a temporary aperture scale for your shutter by copying the markings on the failed shutter's scale to a piece of tape and placing it on the good shutter.

f11 on a 72mm lens is not the same diameter opening as f11 on a 90mm lens.

Right??

fX = focal length/hole diameter

7. ## Re: help! How do I calculate f-stop scale on a copal 0 shutter

Originally Posted by C_Remington
f11 on a 72mm lens is not the same diameter opening as f11 on a 90mm lens.
That's correct, but not relevant to the discussion in this thread.

The OP has a lens with a broken shutter, and wants to replace that with a good shutter of the same model.

He needs to transfer the lens cells and the aperture scale from the old shutter to the new shutter.

No change in the optics is suggested.

- Leigh

8. ## Re: help! How do I calculate f-stop scale on a copal 0 shutter

Just figure out your actual f/stop. Measure the bellows extension and aperture (through the front element), and divide the first by the second.

9. ## Re: help! How do I calculate f-stop scale on a copal 0 shutter

Originally Posted by Leigh
Why not transfer the scale from the broken one to its replacement?

They're just held on by two screws.

- Leigh
and Copal shutters have TWO scales so, if you transfer one scale you should get one correct scale for each set of lens cells ?
so long as the Nikon unit doesn't have some weird Nikon specific modification...

10. ## Re: help! How do I calculate f-stop scale on a copal 0 shutter

Originally Posted by Andrew
so long as the Nikon unit doesn't have some weird Nikon specific modification...
The only Nikon-specific mod that I know of is going to seven shutter blades vs five in the #0 shutter.
This is indicated by a capital N in a circle on the aperture plate.

- Leigh