Non-standard shutter speed and meters

Shootar401 · Mar 2, 2017

I have two cameras one from the 1950's that shoots a rock solid 1/52nd shutter speed and the other a very accurate 1/42nd.

My meter (seekonic L-508) doesn't do custom shutter speeds or any non-standard ones so my question is if I shoot lets say 50asa film and I want to use my meter at 1/60 do I compensate up or down to make change to 1/52 and 1/42?

Do I rate my 50ASA film at 64 or 40? or something else?

Thanks

Dali · Mar 2, 2017

Honestly, the difference is so little that you would be hard pressed to see the difference between 1/60, 1/52 and 1/42.

R.Gould · Mar 2, 2017

Very few of my cameras have standard IE modern shutter speeds, for instance 100 rather than 125 and 300 instead of 250, etc, I just use the nearest speed, 100 when 125 is given, I only use these cameras,folders and such, all from the 30's to late 50's, I never compensate, I only use b/w film and never had a problem, it does not seem to make any difference, maybe with color it would be different, but I find with black and white the difference is so slight as to make no difference, just use the nearest speed, 50 instead of 60 Etc and you will be fine, and just rate your film at box speed, I do and have done so for many years, I have this type camera for at least 15 years, box speed and nearest shutter speed, The alternative is to get a Weston Master 5 or Euromaster which will give you the 50/25/100 Ect
Richard

wiltw · Mar 2, 2017

Difference between 1/60 and 1/52 is only 15%...about 1/6 EV
Difference between 1/60 and 1/42 is about 30%...about 1/3 EV

Taking a reading at 1/60, and then setting 1/42 shutter would result in 1/3 EV more light than read by the meter, so you could set the meter to ISO 320 rather than ISO 400, which results in a reading of 1/3 EV more exposure when the shutter speed on the meter is 1/60 and camera is set to 1/42.

As others have stated, the difference is small enough that I would not worry about it...in the course of metering scenes YOUR error is probably greater in magnitude!

Jim Noel · Mar 2, 2017

wiltw said:
Difference between 1/60 and 1/52 is only 15%...about 1/6 EV
Difference between 1/60 and 1/42 is about 30%...about 1/3 EV

Taking a reading at 1/60, and then setting 1/42 shutter would result in 1/3 EV more light than read by the meter, so you could set the meter to ISO 320 rather than ISO 400, which results in a reading of 1/3 EV more exposure when the shutter speed on the meter is 1/60 and camera is set to 1/42.

As others have stated, the difference is small enough that I would not worry about it...in the course of metering scenes YOUR error is probably greater in magnitude!

AMen!

chrisaisenbrey · Mar 2, 2017

wiltw said:
Difference between 1/60 and 1/42 is about 30%...about 1/3 EV

I rather get half a stop for 1/42 (from 1/60):

60/42=1.43=sqroot (2.04)

But in practice this doesn’t matter.

BrianShaw · Mar 2, 2017

Yes, in practice...

wiltw · Mar 3, 2017

chrisaisenbrey said:
I rather get half a stop for 1/42 (from 1/60):

60/42=1.43=sqroot (2.04)

But in practice this doesn’t matter.

Uh, if we look at shutter speeds on a camera that has

1/3 EV increments...1/60, 1/50, 1/40, 1/30
and in 1/2 EV increments... 1/60, 1/45, 1/30

I dare say 1/42 sec. is closer to 1/40 sec. than it is to 1/45 sec....

1/40 sec. to 1/42 sec. to 1/45 sec.
0.025 sec. to 0.0238 sec. to 0.0222 sec
...or a difference of 0.0012 sec. vs. 0.0016 sec.

GRHazelton · Mar 3, 2017

Perhaps if you shoot slide film you might have a concern, but probably not a problem. When I shot Ektachrome with a Praktica LTL I underexposed from the stated ASA by a little - i.e. shot 64 speed at ASA 80 and all was lovely. I never checked the Praktica's shutter. BTW after about 40 years that commie box still sounds accurate! As others have said, with BW or C-41 not to worry!

Leigh B · Mar 3, 2017

wiltw said:
I dare say 1/42 sec. is closer to 1/40 sec. than it is to 1/45 sec....

1/40 sec. to 1/42 sec. to 1/45 sec.

0.025 sec. to 0.0238 sec. to 0.0222 sec

...or a difference of 0.0012 sec. vs. 0.0016 sec.

Sorry... It doesn't work that way.

1/2 sec to 1 sec is one full stop, with a delta of 0.5 seconds.

4 sec to 8 sec is one full stop, with a delta of 4 full seconds.

- Leigh

Doremus Scudder · Mar 3, 2017

Just for easy reference: Shutter Speeds in approx. 1/3-stop intervals (whole stops bold):

1 sec., .80 sec. (4/5 sec.), .64 sec. (2/3 sec), ½ sec., .4 sec. (2/5 sec.), 1/3 sec., ¼ sec., 1/5 sec., 1/6 sec.,

1/8 sec., 1/10 sec., 1/12 sec., 1/16 sec., 1/20 sec., 1/25 sec., 1/30 sec., 1/40 sec., 1/50 sec., 1/60 sec.,

(continue the above row, adding a zero to the denominator, e.g., 1/8 = 1/80, etc.).

If you see a resemblance to film-speed numbers in the above, it's no coincidence; they run in 1/3 stops as well:

ASA/ISO 8, 10, 12.5 16, 20, 25, 32, 40, 50, 64,
.............80, 100, 125 (continue the row above, just adding a decimal place)

If you know your film speed scale, you know your shutter speeds in 1/3 stops. Interesting to note is that the shutter speeds 1/30 sec., 1/60 sec., etc. are rounded off. There are other adjustments in the shutter-speed scale too that result in speeds being 10-15% different than "ideal." In practice, these small differences are insignificant. Third-stops are useful intervals to calculate with because they correspond to film-speed and most other logarithmically-derived exposure scales.

So, for the OP: 1/50 sec. is ~1/3-stop more exposure than 1/60; adjust your aperture accordingly.
1/40 sec. is ~1/3 stop less exposure than 1/30 sec.; adjust your aperture accordingly. If you don't have an aperture scale marked in 1/3-stop intervals, estimating visually is way close enough.

Best,

Doremus

chrisaisenbrey · Mar 3, 2017

wiltw said:
Uh, if we look at shutter speeds on a camera that has

1/3 EV increments...1/60, 1/50, 1/40, 1/30

and in 1/2 EV increments... 1/60, 1/45, 1/30

I dare say 1/42 sec. is closer to 1/40 sec. than it is to 1/45 sec....

1/40 sec. to 1/42 sec. to 1/45 sec.

0.025 sec. to 0.0238 sec. to 0.0222 sec

...or a difference of 0.0012 sec. vs. 0.0016 sec.

Ok, it looks a little pedantic, but it is based on a quite important principal problem:
EV or stop is a logarithmic scale on the base of 2. That means that we can’t simply divide it linearly.

I’ve never seen a 1/3 incremented shutter speed scale, but it would look like that:

1/60, 1/48, 1/38, 1/30

And a ½ incremented shutter speed scale would indeed look like that:

1/60, 1/42, 1/30

So for a precise calculation:

log_2(60/42)=0.51 ~ 1/2

log_2(60/52)=0.21 ~ 1/5

paul ron · Mar 3, 2017

10% is usually considered very good but that can vary up to almost 50% in old very heavily used shutters.

The main thing is how consistent your shutters are. You can compensate for each individual shutter as needed on your meter, as long as your shutter is constant.

RalphLambrecht · Mar 3, 2017

Shootar401 said:
I have two cameras one from the 1950's that shoots a rock solid 1/52nd shutter speed and the other a very accurate 1/42nd.

My meter (seekonic L-508) doesn't do custom shutter speeds or any non-standard ones so my question is if I shoot lets say 50asa film and I want to use my meter at 1/60 do I compensate up or down to make change to 1/52 and 1/42?

Do I rate my 50ASA film at 64 or 40? or something else?

Thanks

as someone said already;use the closest speed.

Dan Fromm · Mar 3, 2017

Shootar, you should be able to get a dead Weston Master V for no more than $10 delivered. Get one. Don't pay to have it resurrected, even if it can be, just use its calculator dial to read the appropriate f/stop at 1/40 or 1/50 given the f/stop your Sekonic recommends at 1/60th. Or any other shutter speed, for that matter. Alternatively, shell out for a good one and do what it says.

wiltw · Mar 4, 2017

Leigh B said:
Sorry... It doesn't work that way.

1/2 sec to 1 sec is one full stop, with a delta of 0.5 seconds.

4 sec to 8 sec is one full stop, with a delta of 4 full seconds.

- Leigh

I was showing that 1/42 is closer to a speed which is 1/3EV faster from standard speed (1/30) and farther from the 1/2EV faster speed (1/45). So in rounding to the nearest speed, one would round town from 1/42 to 1/40, not round up from 1/42 to 1/45! As Ralph has stated, "use the closest speed".

Some meters only have 1/2EV shutter speeds, but they do have 1/3EV ISO steps.

Non-standard shutter speed and meters

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