Shutter speeds on new Copals versus old Compurs

[Cor]

I have literally this mixed bag of lenses when I go out with my 4x5. Some are mounted in Copal (Press) shutters, other in older Compur shutters.

The Copals have the modern range of shutter speeds: 1, 1/2, 1/4, 1/8 etc.

The Compurs run the older set: 1, 1/2, 1/5, 1/10, 1/25, 1/50.

I sometimes have problems to translate the readings of my spot meter to the Compurs.

Ok 1 and 1/2 no sweat, and faster than 1/60 I almost never use. But a reading of 1/4 sec: using 1/5 sec is a bit too short than, and than what about a reading of 1/8; put the Compur on 1/5 or 1/10 ?.. and so on..

I am a bit ambivalent on this though, realizing that the shutter speeds are not exact anyway, and I shoot only B&W only, so there is leeway. Usually I choose the longest speed, a bit over exposure won't hurt, underexposure can.

How do you folks handle above issue?

Thanks,

Best,

Cor

[Vick Vickery]

Guess I'm too old to worry about it...for years I've been just adjusting my aperature a little to compensate for the difference; in practice it works fine: if your meter tells you 1/60 at f16, just use 1/50 and stop down a hair past f16 toward f22. You're talking about way less than 1 stop anyway...my metering isn't that accurate to start with!

[Cor]

Good point, Vick,

Forgot to mention that, I also use that method, but with my beloved 120 Angulon in a Compur the f-stop scale spacing gets progressivly narrower (logarithmic?) so moving up or down 1/3 of a stop is a bit difficult and isn't very precise I guess.

Cor

Guess I'm too old to worry about it...for years I've been just adjusting my aperature a little to compensate for the difference; in practice it works fine: if your meter tells you 1/60 at f16, just use 1/50 and stop down a hair past f16 toward f22.

[BrianShaw]

For B+W and C41 use the nearest and don't worry. For E6 correct for the difference with a little more or less aperture.

[Leigh]

The actual shutter speeds should be the same; only the labels differ.

The real speeds are:
1
1/2
1/4
1/8
1/16
1/32
1/64
1/128
1/256
1/512
1/1024

Each of these differs from its neighbors by exactly a factor of two, as required by the law of reciprocity.

You should be able to map either set of labels into that sequence to see which corresponds to which.

- Leigh

[Cor]

I am not sure I am following you on this one, I understand that some rounding off takes place, so the "new" set is more consistent than the old one (ie from 1/10 to 1/25), my question was more a practical one, when your meter gives a reading of 1/8 seconds, go for 1/10 or 1/5..

The actual shutter speeds should be the same; only the labels differ.

The real speeds are:
1
1/2
1/4
1/8
1/16
1/32
1/64
1/128
1/256
1/512
1/1024

Each of these differs from its neighbors by exactly a factor of two, as required by the law of reciprocity.

You should be able to map either set of labels into that sequence to see which corresponds to which.

- Leigh

[Frank Petronio]

Just knock the aperture a hair one side or the other if needed.

[Frank_E]

I was concerned about my shutter speeds so I purchase a tester of ebay and was suprised in the variation of the real speeds from the actual
I would think that is the best solution find out what the shutters are actually experiencing and use those numbers

[Leigh]

when your meter gives a reading of 1/8 seconds, go for 1/10 or 1/25..

You definitely go for the closest one, so in this case 1/10.

To use the list that I gave previously, print it out and write the "modern" shutter speeds next to the real speeds. For example:
1/8 is shown as 1/8
1/16 is shown as 1/15
1/32 is shown as 1/30
1/64 is shown as 1/60
1/128 is shown as 1/125

Then do the same for your Compur shutter, writing one speed per line starting at 1 second. This will show you which Compur labels correspond to which real speeds.

- Leigh

[Cor]

You definitely go for the closest one, so in this case 1/10.

To use the list that I gave previously, print it out and write the "modern" shutter speeds next to the real speeds. For example:
1/8 is shown as 1/8
1/16 is shown as 1/15
1/32 is shown as 1/30
1/64 is shown as 1/60
1/128 is shown as 1/125

Then do the same for your Compur shutter, writing one speed per line starting at 1 second. This will show you which Compur labels correspond to which real speeds.

- Leigh

Ok

Btw I made a typo, 1/25 should read 1/5, sorry about that

Cor