Shutter Testing - What do the numbers mean?

Renato Tonelli · May 25, 2007

I was just give a shutter tester. It is exactly the same as Calumet's but the writing on its body is completely faded from years of handling and there was no manual. I checked Calumet's web site but no PDF manual either - I called them to see if I can buy a manual from them but it will take time... Anyway, the thing seems to work and I proceeded to test a Schneider 210 BUT I have no idea what the numbers mean. The numbers also fluctuate on repeated test on the same shutter speed, although by very little. If these numbers make sense to you, would you be so kind as to let me know what they mean? Are the speeds correct or otherwise? Thanks.

Tested Shutter Number given by Shutter Tester
Speed
1/2 46753
1/4 24030
1/8 12967
1/15 6325
1/30 2630
1/60 1853
1/125 1044
1/250 662
1/400 558

ineffablething · May 25, 2007

The second number is fractions of a second. So, there should be a decimal point in front of the numbers. For example, 1/2 second is also .5 second. You shutter is running slightly faster than that, it's at .46 second. Your 1/4 second is also fast, running at .24 sec instead of .25 second and so on.

W.

Renato Tonelli said:
I was just give a shutter tester. It is exactly the same as Calumet's but the writing on its body is completely faded from years of handling and there was no manual. I checked Calumet's web site but no PDF manual either - I called them to see if I can buy a manual from them but it will take time... Anyway, the thing seems to work and I proceeded to test a Schneider 210 BUT I have no idea what the numbers mean. The numbers also fluctuate on repeated test on the same shutter speed, although by very little. If these numbers make sense to you, would you be so kind as to let me know what they mean? Are the speeds correct or otherwise? Thanks.

Tested Shutter Number given by Shutter Tester
Speed
1/2 46753
1/4 24030
1/8 12967
1/15 6325
1/30 2630
1/60 1853
1/125 1044
1/250 662
1/400 558

Frank R · May 25, 2007

I just scanned two things: a form I use when testing shutters, and the label on the front of the shutter tester.

Notice the acceptable ranges for a given shutter speed.

I copy and paste four of the forms on a single sheet of paper and print them out. I test a shutter and write down the speeds on the form. Then I cut the form and keep it with the shutter. If I am selling a shutter, I include it in the plastic bag so the purchaser will know how accurate their shutter is.

Frank R · May 25, 2007

I hope you can read that. APUG shrank the file size from the file I posted.

Curt · May 26, 2007

1/4 second is-- .25

1 second is---- 1.0

If you were looking for a 1/4 second and got .25 you would be right on. If you get less then it is slow at that speed and if you get a higher number then it is fast. How much? You will have to do the math for 1/3 or 1/2 stop differences.

Warm up the shutter a few times then do a run of three and average. It's mechanical and not as precise as you might think, so average.

Worse is when it's warm or cold, it slows down and speeds up depending on the weather. Then there is the position of the shutter, was it pointed down or up or on the side, any of these might change the friction and the mechanics.

Good luck,
Curt

jstraw · May 26, 2007

I recommend that you do a series of tests for each speed and average the readings.

Curt · May 26, 2007

Franks photos are right on for the information needed.

Frank R · May 26, 2007

A few more tips:

Wait a few seconds after cocking the shutter and before firing. If you do it too quickly you will get inaccurate readings.

The shutter is a mechanical device that you are measuring in milliseconds; you will notice variations. But I often notice that some speeds will be very consistent. Pretty remarkable for 50 year old shutters.

Renato Tonelli · May 26, 2007

Thank you all for helping me sort it out. It's making sense now.

craigclu · May 26, 2007

I've got the same timer (pre-Calumet) and it also has this sticker on it. I just looked and the original manual isn't where I suspected it to be filed but I'll scan a PDF if I stumble into it and post back to this thread.

craigclu · May 26, 2007

I just remembered an old spreadsheet that I was using when wringing out my gear some years back. It generates a graph showing the ƒ stop deviation and the erratic variation of the shutter, too. The procedure is to run through the shutter speeds at one firing per speed from slowest to the fastest, then from the fastest to the slowest and another run from slowest to fastest. The idea of this is to see the effect of shutter spring/mechanical condition coming from both directions. If you enter your results in the spreadsheet, it will represent the ƒ stop deviation on the right hand Y axis (the solid line) and also show the erratic nature of your shutter on the right axis in %.

The site won't allow uploads of spreadsheets or zip files (I couldn't see a method, anyway) so I'm attaching a shot of the graph element. Let me know if you want a copy of the spreadsheet and I'll bounce one to you. It isn't really a "ready-for-prime time" item but I used it for quick snapshot views of my shutters. It might make for a good starting point for someone to tune up some more.

Shutter Testing - What do the numbers mean?

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