Have you tested your shutters lately?

[Daniel Grenier]

Greetings;

FYI, I just had my 4 Copal 3 shutters tested by a repair Lab to see what exactly the difference in speeds are from the indicated speeds and from each other. The point of this was to determine the "real" speeds for all my shutters as erratic results in film exposures made me question some speeds' accuracy for some of my lenses (165mm to 480mm for 8x10).

In the Lab, all shutters were tripped at least ten times per speed for more accurate results. The results were quite surprising.

1- ALL speeds from 1s to 1/8s were slow by 5% to 20%.

2- 1/15 and 1/30 speeds were all slow from 5% to 25%.

3- 1/60 and 1/125 were way off (slow too) from 40% to 60%

My shutters are all over 15 years old and they are all in a good state of repair and cleanliness. They just got very "lazy" and slow with time - to varying degrees. It does not really matter that they're off as long as yow know by how much so that you can compensate properly.

Why am I telling you this? Many are testing new films, developers, processing methods etc. without realizing that some shutter speeds are way off which, in turn, troughs one more curve in your testing. Not to mention "real" photography headaches caused by this.

Anyhow, thought some of you might be interested and some of you will definitely want to confirm those shutter speeds.

Cheers.

[Arne Croell]

Actually, In don't find these values "way off". You have to take into account that a timing error of 25 percent is actually a little less than 1/3rd of stop in exposure - 1/3rd of a stop is a factor of 1.2599 (3rd root of 2) , or 26% in timing. 40% is close to half a stop (factor 1.41, square root of 2).

For the short speeds, one has to take into account what is called "shutter efficiency" - that is, the measuring sensor will respond already to a partially opened shutter and thus indicates more exposure than really present, since the shutter acts as a stop and lets through only part of the light. This is more pronounced with larger shutters like your number 3. With standard shutter testers, like the Calumet one, the measured highest speed is usually 30-50% longer than the indicated one even for new shutters-exact values depend on lighting conditions etc.

I do agree that regular checking and consistent habits is a good idea, but don't think your values indicate anything to worry about.

[Richard Boulware]

I agree with Daniel. I use a Delta SH-T2 (Canada) after trying a non-operating model from Calumet which I returned. The Delta is an excellent unit. My lenses for my Linhof Technika, are all tested for true speeds vs. indicated, and it DOES make a difference.

Most of my new lenses (Grandigon) are within 10% but some of the older lenses, even after service, are off quite a bit. I carry a card indicating true speeds of each of my lenses. Oddly enough, the most accurace shutter I have is the Linhof shutter in my 75mm Zeiss Biogon, which is within 3% of being dead on. Perhaps it is the old addage, you get what you pay for.

I believe I purchased my Delta from MicroTools.

For all those on this board who are technically 'obsessed', it is very funny to me that most of them...most often, have no idea of the true shutter speed they are using, which often can be a critical factor for shooting things like moving water, trees moving in the wind, etc.

Be well, Richard Boulware - Denver.

[Richard Fenner]

I took mine to the local repairer late last year, and on his testing equipment all were within 10%; however, some were at different ends of that range, so he adjusted them all to within a few percent, and in the same direction. It was fairly cheap too.

Given the variability in metering with a polariser (and not bracketing 8x10 e6!), I'm often amazed at my almost univerally good exposures. You don't want the meter off a bit, the shutter off a bit, and the gueswork for the polariser off a bit!

[Arne Croell]

Richard B., I just checked on the Delta description and it allows for some shutter efficiency effect through its sensor bias adjustment and the advice to place the photo cell half way between center and rim of the shutter. Simpler ones like the Calumet do not allow that (the bias adjustment) so easily. That might explain the difference to your results (for the fast speed) The best would be a photo cell connected to an oscilloscope to test it, but thats a rather expensive solution. It somewhat depends on with what and how Daniels repair shop tested, but the values for the fast times let me suspect it is due to the testing method not accounting for efficiency. In my experience shutters that do have problems usually have them in the slow speeds, not the fastest ones.

[Andrew O'Neill]

".....I believe I purchased my Delta from MicroTools."

Richard B., where abouts is Micro Tools? Do they have a website?

[Arne Croell]

<a href="http://www.micro-tools.com/">
http://www.micro-tools.com<a>

[Neal Shields]

I have had old shutters apart so this shouldn't have suprised me but it did.

I have shutters where, for example, the slow speeds are slow, the medium speeds are fast and the fast speeds are slow.

I just keep cheat sheets in my camera case for each lens and test about once a year.

[Andrew O'Neill]

Thanks Arne!

[Richard Boulware]

Micro-tools is at.....www.micro-tools.com, or type in Micro-tools on Google.