PDA

View Full Version : help! How do I calculate f-stop scale on a copal 0 shutter



Dan Dubowitz
9-Jan-2014, 17:52
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

Mark Stahlke
9-Jan-2014, 18:15
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.

Mark Woods
9-Jan-2014, 18:22
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.

Mark Stahlke
9-Jan-2014, 18:51
Let me know when you replace your shutter. I hav need of some Copal 0 parts.

Leigh
9-Jan-2014, 19:34
Why not transfer the scale from the broken one to its replacement?

They're just held on by two screws.

- Leigh

C_Remington
9-Jan-2014, 20:06
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.

I'm not certain but, something doesn't smell right about this.

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

Right??

fX = focal length/hole diameter

Leigh
9-Jan-2014, 20:10
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

Mark Sawyer
9-Jan-2014, 23:16
Just figure out your actual f/stop. Measure the bellows extension and aperture (through the front element), and divide the first by the second.

Andrew
10-Jan-2014, 14:29
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...

Leigh
10-Jan-2014, 19:14
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

Arne Croell
11-Jan-2014, 13:38
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...
There is one problem with the Nikon versions, their aperture scales are printed directly on the main aluminum strip that surrounds the whole shutter, and not on the two smaller strips held with two screws each as in other lenses. There are also no screw holes in those places - the threads may be below that main aluminum strip, but are not directly accessible. Not an insurmountable problem - for a temporary solution one could use double-sided sticky tape to hold the old shorter aperture scale in place.