The inaccuracy of fast speeds on mechanical cameras.

Radost · Apr 15, 2025

I finally purchased a 3 sensor shutter meter. My leica/Minolta CL were pretty much the same at fast shutters.
This is what i found on all 3:
1000 is 600
500 is 400
250 is 250
125 is 110

+- 5%
I have maybe 25 more mechanical cameras to check

Are mechanical cameras all slow over 250?

My 3 Minolta CLE were +-5%

BrianShaw · Apr 15, 2025

Often that’s the case with the highest speed, for a wide variety of reasons. There’s plenty of speculation about causality, much of which seems plausible but unproven. But what are your expectations? Shutter speed accuracy is generally accepted to be plus/minus 1/3 stop.

With that knowledge you can now compensate with aperture so there’s little concern unless the speeds are not consistent. Or there’s the additional reality that there’s so much variability at each stage of the photographic process that as long as the negs are decent then all is well.

Paul Howell · Apr 15, 2025

Given the years, state of lubricants, tension of springs it is not all that uncommon. My mechanical shutter cameras are all over the map, as much as 3 stops off. When I had a Nikon F and F2 I had them serviced once a year by Nikon and my Pentax Spotmatic maybe every other year to keep within tolerance of 1/2 stop.

loccdor · Apr 15, 2025

Do the leaf shutters keep their high speeds better than focal plane?

Alan Edward Klein · Apr 15, 2025

Radost said:
I finally purchased a 3 sensor shutter meter. My leica/Minolta CL were pretty much the same at fast shutters.
This is what i found on all 3:
1000 is 600
500 is 400
250 is 250
125 is 110

+- 5%
I have maybe 25 more mechanical cameras to check

Are mechanical cameras all slow over 250?

My 3 Minolta CLE were +-5%

How did you test? What is the accuracy of the test measurements? Shutters are easier to verify at a quarter of a second then they are at 1000th of a second.

Paul Howell · Apr 15, 2025

loccdor said:
Do the leaf shutters keep their high speeds better than focal plane?

A good question, one that I've read both yes and no, but when testing film and developer combos over the years my Kowa and Mamiya press lens seem to be very close to top speed of 1/500, within a stop.

Chan Tran · Apr 15, 2025

Even electronically timed shutters are not very accurate at high speed. Low speeds they are significantly more accurate than pure mechanical shutter. You finding is typical not a surprise.

Chan Tran · Apr 15, 2025

Paul Howell said:
A good question, one that I've read both yes and no, but when testing film and developer combos over the years my Kowa and Mamiya press lens seem to be very close to top speed of 1/500, within a stop.

Within a stop which means 1/500 can be 1/1000 or 1/250?

loccdor · Apr 15, 2025

I don't know if I've ever seen a speed go faster than it should, it's always slower.

F4U · Apr 15, 2025

loccdor said:
Do the leaf shutters keep their high speeds better than focal plane?

No. Iris shutter accuracy is TERRIBLE. No exceptions, unless it's brand spanking new. the deal with iris shutters is to get a shutter tester, find out the most accurate speeds, which will be 1 or 2, and use them.

250swb · Apr 15, 2025

Knowing your camera is the solution. If it consistently gives the same + or - shutter speeds that's all you need to know. You could send it off for a CLA, but to my mind that is when something beyond compensating for less than half a stop here or there is required.

BrianShaw · Apr 15, 2025

F4U said:
No. Iris shutter accuracy is TERRIBLE. No exceptions, unless it's brand spanking new. the deal with iris shutters is to get a shutter tester, find out the most accurate speeds, which will be 1 or 2, and use them.

Assuming that the leaf shutter is in good mechanical condition and properly serviced, they actually can be quite accurate… well within the acceptable specification deviations. What makes some folks think they are not accurate seems to often be a lack of understanding about shutter efficiency. That variability is simply a fact of life and should be understood, especially when testing shutter speed and using flash bulbs as it does impose a significant effect. The other reason is unrealistic expectations of shutter speed accuracy.

Paul Howell · Apr 15, 2025

Chan Tran said:
Within a stop which means 1/500 can be 1/1000 or 1/250?

Maybe 20 years ago I had my Mamiya press 100 3.5 serviced by Phoenix Camera Repair (no longer in business) it was a full stop fast, so 1/1000 of second which seemed to be unlikely to me, I only know of few fast leaf shutters, the Kodak 1/800 in the Tourist and the Graphic lens for the super at 1/1000. The Mamiya underexposed by a stop. Once it was serviced it was spot on. My Yahsica D seems to be a stop slow, the Kowas might be a bit slow as they tend to overexpose a bit and I shoot at higher ISO than I do with electonic shutters.

xkaes · Apr 15, 2025

Those higher speeds are harder to achieve on mechanical focal plane shutter cameras. That's why just about every camera company -- back in the mechanical SLR heydays -- offered a top-end camera with 1/1,000 top speed, as well as a less expensive brother with a top speed of only 1/500. For example, that was the case with Minolta's first SLRs in the 1950s -- the SR-2 (1/1,000) and the SR-1 (1/500), and well as their 1970's SLRs -- the SRT102 (1/1,000) and the SRT100 (1/500). It was the same with the Pentax Spotmatic SP1000 vs SP500, the Mamiya MSX 1000 vs MSX 500. The list goes on.

MattKing · Apr 15, 2025

F4U said:
No. Iris shutter accuracy is TERRIBLE. No exceptions, unless it's brand spanking new. the deal with iris shutters is to get a shutter tester, find out the most accurate speeds, which will be 1 or 2, and use them.

This doesn't match the experience of my camera repair friend - who has decades of professional level experience.
He tested a bunch of such shutters on a bunch of different cameras for us at my Darkroom Group, and many of them were leaf shutters.
The fastest speeds were usually a bit slow - 1/2 a stop at the outside, but many of them were within a 1/3 of a stop for most speeds.
And those cameras and shutters were of all sorts, as well as a lot of different vintages, and a lot of different exposure to regular maintenance.
This includes the shutter in my Zeiss Ikon whose lens was manufactured in 1939.
One thing to be aware of though - some shutter testers are better set up for testing focal plane shutters.

loccdor · Apr 15, 2025

From exposing slide or thin-latitude negative film:

My Kiev-4 mechanical focal plane shutter seems uniformly about 1/2 stop slow on all high speeds
Autocord and Olympus Pen D leaf shutters (newly serviced) are good, maybe 1/3 stop slow at the most
My Olympus XA2 is 2/3 stop fast but that's an internal light meter thing (electronic leaf?)
The Canon T90 (serviced professionally) and Canon EOS Elan 7E (cleaned shutter blades with alcohol) are very accurate even to 1/4000 (electronic focal plane)

Paul Howell · Apr 15, 2025

The Canon T90 and EOS 7E are electronic shutters, all of my electronic shutters, Nikon, Pentax, Chinon and Minolta are all spot on.

Les Sarile · Apr 16, 2025

Radost said:
I finally purchased a 3 sensor shutter meter. My leica/Minolta CL were pretty much the same at fast shutters.
This is what i found on all 3:
1000 is 600
500 is 400
250 is 250
125 is 110

+- 5%
I have maybe 25 more mechanical cameras to check

Are mechanical cameras all slow over 250?

My 3 Minolta CLE were +-5%

Your CL has a horizontal shutter doesn't it?

A new Nikon FM2 reviewed by Pop Photo 12-1982 shows the Nikon FM2 they tested looks better above 1/125 all the way to 1/4000 then in the low speeds. I wonder how consistent these performance tests are across more than 1 sample?

PP1982-12 by Les DMess, on Flickr

abruzzi · Apr 16, 2025

F4U said:
No. Iris shutter accuracy is TERRIBLE. No exceptions, unless it's brand spanking new. the deal with iris shutters is to get a shutter tester, find out the most accurate speeds, which will be 1 or 2, and use them.

even new they can be less than ideal. A while back I stumbled across a camera magazine review of the new Bronica SQ. They tested the shutter speed which was fairly accurate across all speeds except 1/500 which was about a half a stop slow. Since most of my cameras are leaf shutter based, I almost always avoid the top speed (usually 1/500) but if I do use it I close the aperture a half stop from the metered speed to counter the slower shutter speed.

Alan Edward Klein · Apr 16, 2025

Paul Howell said:
The Canon T90 and EOS 7E are electronic shutters, all of my electronic shutters, Nikon, Pentax, Chinon and Minolta are all spot on.

My Nikon N6006 electronic shutter seems to be right on as well. Amazing for a 35 year old camera.

ic-racer · Apr 16, 2025

Radost said:
Are mechanical cameras all slow over 250?

Your cameras are. Not mine

Time to have them cleaned, or just note the shutter speed and adjust exposure as needed.

What bothers me most is inconsistet timing of the second curtain. This camera got relinquished to the parts bin.

2ndGenNikonian · Apr 16, 2025

Timing mechanical shutters at high speed is always difficult, so electronic shutters will always be more accurate at high speeds. Most mechanical shutters fresh from the factory were generally within 1/3-1/2 stop in accuracy, which is good enough for most work.

Seconding the people saying to get it CLA'd. Even the best mechanical SLRs are decades old, and that can cause all sorts of problems with lubricants, spring tension, and the like. On the plus side, as long as there isn't anything catastrophically wrong, you can usually get them CLA'd back to the aforementioned manufacturers' tolerances.

BMbikerider · Apr 16, 2025

Is there any reason why a focal plane shutter should not give an accurate speed? The curtains at whatever speed should travel at the same speed with only the slit or gap between them which governs the speed differing. So long as it is accurately set up and serviced regularly (like anything else man made) it will perform as it should.

I have a very late Nikon F2a (Probably 1980/81 which I think judging by its general condition has seen very little use, (no paint missing or dents) and the shutter seems perfectly in sync with the sound as it is operated and the speed marked on the shutter dial. I have yet to have a bad exposure which was the cameras fault - it is always mine! Even the meter is accurate when compared with my F6 and a seperate hand held meter (Minolta Autometer 3)

SalveSlog · Apr 16, 2025

I believe that leaf shutters at high speeds are slower for small apertures than fully open.

Because if you need the lens to be fully open the film will only get enough light after the leafs has traveled fully out of the way. And as soon as they start traveling back, the light will be reduced.

With the smallest aperture set the film will get the needed light as soon as the leafs start to open and receive light all the time until they're almost closed again. That takes longer time.

This difference will be irrelevant at slow speeds, but at 1/500 or 1/1000 probably significant (?)

Radost · Apr 17, 2025

ic-racer said:
Your cameras are. Not mine

Time to have them cleaned, or just note the shutter speed and adjust exposure as needed.

What bothers me most is inconsistet timing of the second curtain. This camera got relinquished to the parts bin.

What sensors did you use

The inaccuracy of fast speeds on mechanical cameras.

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