View Full Version : Calumet Shutter Tester

21-Jul-2004, 17:32
I have a Calumet Shutter Tester without instruction. I figure the lens goes between the bare bulb and the Tester is correct. But how do I translate the numbers and make compensation? For example:-

1 sec. - 1.04631 against 1.00000, or

1/2 sec. - .49048 against .50000, or

1/4 sec - .23211 against .25000.

Ideally, if someone could be kind to email a copy of the Calumet Shutter Tester manual to me at cello9@joinme.com? Thanks!

Larry Gebhardt
21-Jul-2004, 18:02
I sent you a spread sheet (Excel) that I use with mine to make the calculations quicker.

ronald moravec
21-Jul-2004, 18:41
If these are real checks, you shutter is running well at these speeds.

example 1 sec= 1.0000 desired / 1.0463 actual time so you have 4.63% error long.

example 2 1/2 sec check - .50000 desired / .49048 actual time. So the shutter is running a bit fast by .00952 sec. This is a 2% error

ex 3 1/4 sec check . .25sec is perfect actual is .23211. Lets just round to .23 to keep the math simple. This speed is .02 sec fast . .02 divided by .25 is .8 or 8% error.

All this is is a clock activated by light and it is digital. 1 sec is 1.00000 sec 1/2 sec is .500000 sec 1/4 sec is .250000 sec 1/8 sec is .0125000 sec ( 8 x .0125 = 1) 1/15 sec is 1 divided by 15 or .006250 shown on meter as just 6250 1/30 sec is 1 div by 30 = .003125 shown as just 3125 1/60 sec is 1 div by 60 = .001563 shown as just 1563 1/125 sec is .000781 or shown as 781 1/250 is 1 divided by 250 or .000391 shown as 391 1/500 is .000195 or just 195

I stopping here as large format shutters only go to 1/400. Need the nominal or perfect reading for 1/400. I hope you can figure it out now. Hint - you should get between 195 and 250 without the leading zeros, closer to 195.

The face of the checker has three vertical columns next to the nominal speed.

The first represents no error reading for the speed being checked, the second shows the limits for 1/6 stop error and the last for 1/3 stop limits.

Look at 1/125 sec. if you get 781 it is perfect. if your reading is between 877 and 696 you are between plus and minus 1/6 stop. If you get between 984 and 620 you are within 1/3 stop of perfect.

last example- 1/125 perfect is 781. 781 to 877 is between perfect and plus 1/6 stop. 781 to 696 is between perfect and minus 1/6 stop.

one more- 877 to 984 is between 1/6 and 1/3 over 696 to 620 is between minus 1/6 and minus 1/3.

SA stamped envelope will get you a copy of the instructions. if you still need them.

21-Jul-2004, 22:14
Thanks Larry, but I just couldn't open the file as I do not have Excel. I'll get help to open it soon.

Thanks also to R.Moravec. Always takes me a longer time to absorb numbers. But I'll get it eventually. Really appreciate the time taken for the explaination.


21-Jul-2004, 23:47
Yes! I got it. Thanks!

22-Jul-2004, 10:27
I haven't seen Larry's spreadsheet (I'd like to see it... Could I get a copy?), but it occurs to me that it may be a worthwhile addition to the LF home page if the powers that be concur.


Larry Gebhardt
22-Jul-2004, 10:31
William, I sent you a copy. It currently contains a section for each of my lenses. I could update it and clean it up if ou think it would be useful for the comunity.

ronald moravec
22-Jul-2004, 15:19
Arron, I bet you have excell burried in the office programs that came with the computer. It is probably a cut down version, but still useful.

23-Jul-2004, 08:00
R.Moravec, I explored the XP OS but no scale-down version of Excel. It's okay, I'm able to get help. Thanks again.