Calibration of Copal Shutters

[Spencer Ladd]

What is the best way to calibrate my copal shutters? I have small differences between each one... bellow extension has been calculated.

Can I do it myself, affordably, or do I need to take the lenses to a shop?

[domaz]

I think you will find it extremely difficut to CLA a shutter yourself and make it actually fire at the speed it's supposed to. Most DIY shutter jobs are just to get them running again if they are sticking or not running at all. How off calibration are we talking? 1/2 stop? 1+ stops?

[Kevin Crisp]

If you mean they are not running at perfect times, then you will have a really hard time getting there. Small changes are hard to make if the shutter does not otherwise need a CLA. With a CLA they will generally run within a 1/4 to a 1/6th stop of the marked speeds. They will not be accurate at 1/125th and above in my experience, even when brand new out of the box.

[Spencer Ladd]

I think you will find it extremely difficut to CLA a shutter yourself and make it actually fire at the speed it's supposed to. Most DIY shutter jobs are just to get them running again if they are sticking or not running at all. How off calibration are we talking? 1/2 stop? 1+ stops?
I have one shutter which is about 2/3 over. All of my shutters are within a 1/4 of each other. I expose chromes and negs, then scan, so I can correct the negs... not the chromes.

I am looking up CLA now... the term has slipped through my net... help me out.

Thanks.

[Spencer Ladd]

If you mean they are not running at perfect times, then you will have a really hard time getting there. Small changes are hard to make if the shutter does not otherwise need a CLA. With a CLA they will generally run within a 1/4 to a 1/6th stop of the marked speeds. They will not be accurate at 1/125th and above in my experience, even when brand new out of the box.
If I could get all my shutters running within a 1/6 of each other I would be very happy. Who can calibrate shutters that well?

[Jack Dahlgren]

I have one shutter which is about 2/3 over. All of my shutters are within a 1/4 of each other. I expose chromes and negs, then scan, so I can correct the negs... not the chromes.

I am looking up CLA now... the term has slipped through my net... help me out.

Thanks.

Clean Lube Adjust

[Spencer Ladd]

thanks.

[Doremus Scudder]

Trying to get all your mechanical shutters calibrated so they run within 1/6 stop of each other is at best Quixotic. It would certainly be time-consuming and expensive to get them within 1/3 stop of each other IMO.

Most shutters are quite consistent, however. so the easier solution is to speed test them all and put a sticker on their individual lensboards with the actual speeds. Use these along with aperture adjustments and you should to about 1/6-stop accuracy (which should be more than accurate enough!). It is then just a matter of setting the right speed on the shutter dial to match the actual speed you desire. This also allows you to use the higher "speeds" with confidence (even though they will likely be much slower than marked).

Have your tech test the shutter several times at an aperture you most often use (f/22 for example) and average the values. Usually shutter testers read in milliseconds, so you can easily convert to fractions of a second from that.

My stickers indicate the closest 1/3-stop, e.g., "1/15+, or 1/60-" where the "+" and "-" signs indicate a higher or lower denominator (faster or slower shutter speed) respectively. This works well with meters calibrated in 1/3 stops and is a lot easier to deal with in the field than "1/42" or the like.



Hope this helps,

Doremus Scudder

[Frank Petronio]

It is funny to hear and see some photographers fine tune their workflow, especially those using the Zone System, to theoretically be accurate to the tenth of a stop.... depending how you count it, there is at least a 1/3 to 1/2 a stop of variance even with careful workflow -- shutters vary, temperature, color of light, various minute factors all compound the margin of error.

Luckily with modern negative films, we can handle that much variation in most circumstances. In the bad old days of shooting transparencies, you simply had to bracket.

[Spencer Ladd]

Trying to get all your mechanical shutters calibrated so they run within 1/6 stop of each other is at best Quixotic. It would certainly be time-consuming and expensive to get them within 1/3 stop of each other IMO.

Most shutters are quite consistent, however. so the easier solution is to speed test them all and put a sticker on their individual lensboards with the actual speeds. Use these along with aperture adjustments and you should to about 1/6-stop accuracy (which should be more than accurate enough!). It is then just a matter of setting the right speed on the shutter dial to match the actual speed you desire. This also allows you to use the higher "speeds" with confidence (even though they will likely be much slower than marked).

Have your tech test the shutter several times at an aperture you most often use (f/22 for example) and average the values. Usually shutter testers read in milliseconds, so you can easily convert to fractions of a second from that.

My stickers indicate the closest 1/3-stop, e.g., "1/15+, or 1/60-" where the "+" and "-" signs indicate a higher or lower denominator (faster or slower shutter speed) respectively. This works well with meters calibrated in 1/3 stops and is a lot easier to deal with in the field than "1/42" or the like.



Hope this helps,

Doremus Scudder
I don't have a tech. I have bracketed in the past. But, film + processing is getting very expensive. So, I would prefer to shoot 1 or at max 2 of each image. Scanning does help. But, not if anything is over exposed.

I do usually shoot around f22 as you indicated and I am willing to label each lens once the variations have been determined.

Where would I find a tech?

[BrianShaw]

I don't have a tech. (snip) Where would I find a tech?

It depends on where you are located.

If you are in the US, I find Steve's Camera Repair in Culver City CA to be a good tech. There are many others, too, but this is who I prefer.

Google "camera repair" + "(your location)" is a good way to start finding a tech.