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View Full Version : Testing Focal Plane Shutter Speeds: Using a Television, Home Made Device, Etc.



Fragomeni
11-Sep-2010, 01:06
I have several antique cameras that I've restored that I would like to use in my photography. Many of them have focal plane shutters capable of speeds up to 1/1000 (Graflex cameras) but in order to use them seriously I need to test whether or not the shutters are performing at the marked shutter speeds and if not I need to adjust them. I've read articles from back issues of old photo magazines describing a method of testing shutter speeds above 1/60 by photographing a television screen and counting the lines on the film. The method is purportedly very accurate. Here (http://books.google.com/books?id=ASoDAAAAMBAJ&pg=PA106&lpg=PA106&dq=check+shutter+speed+tv+screen&source=bl&ots=ICDJgXUqvl&sig=HBEhubkV5hCyG_wXp6JYmAehxmg&hl=en&ei=VTaLTNaNJpO6sQPk5rS9BA&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC8Q6AEwBg#v=onepage&q=check%20shutter%20speed%20tv%20screen&f=false) is a description of the method from the Dec 1967 issue of Popular Science.

Now, does this method work with modern televisions i.e. plasma screens or LCDs? I understand the description of how the image is made on the screen but I'm wondering if this is only true for older televisions and if this is no longer a feasible technique with digital televisions. If anyone has any information on this please let me know. In the meantime I think I'll start building a small shutter speed test as described on Jo Lomman's website here (http://www.xs4all.nl/~lommen9/electronic%20shutter%20tester/index.html).

Any insight into the best way to go about all of this would be very helpful! Thank you.

Brian Stein
11-Sep-2010, 01:51
I believe the method will still work with lcd as they refresh at a given rate, but recommend just going with the simple audio card shutter tester for non-focal plane shutters.
For the first method you actually have to take, process, and analyze the picture: a substantially greater time investment if you are going to look at a number of shutters at many speeds.
For focal plane shutters look at http://www.willegal.net/photo/repair/shuttertester.htm and http://www.largeformatphotography.info/forum/showthread.php?t=26168

Fragomeni
11-Sep-2010, 01:54
Yea, I'm feeling the same way. Testing focal plane shutters via the audio card method is the same as testing any other shutter, correct? Now, to make sure I know how to adjust the focal plane shutters in my cameras! :) Thanks for the input.

Mark Woods
11-Sep-2010, 10:28
Hello Francesco,

I think there are a couple of issues you might think about. The refresh rate is different for different plasma and LCD screens. I have a suspicion that that method was used for old SMPTE Standard Def 525 Interlace CRT screens. Progressive screens might not work, and HD displays might also not work. Finally, the orientation of the camera in relation to the display might compromise you results. What this is, is if the focal plane shutter travels in the same direction as the scan, e.g. from top to bottom. If you orient the camera in the opposite direction, where the FP shutter travels from bottom to top, it will be different. Check around and see if anyone has a better way to time the shutter. My Metrolux enlarger timer will give me read outs for shutter times.

Hope this helps.

Mark

engl
11-Sep-2010, 12:54
If you do not have any equipment for testing, but have a DSLR, you can use the DSLR as a "digital back" for many cameras to test shutters. Keep the shutter you want to test open and get a couple of reference frames with the DSLR at different shutter times, then put the DSLR in bulb mode and take some shots using the shutter you want to test. Match brightness levels to find the real shutter speeds.

I would not want to test a lot of shutters using the above method though. Im not sure what the best way to do that would be, there seems to be major issues with most tests I have seen proposed. From what I understand many shutter testers test with only a single beam, which will not give accurate results for leaf shutters at high speeds, since there is a major difference when measuring the center of the shutter versus the edge, or even when measuring different spots at the same distance from the center. Still, it may be the only way to go for quick testing, and the results should be good for focal plane shutters.

Fragomeni
11-Sep-2010, 20:40
I think there are a couple of issues you might think about. The refresh rate is different for different plasma and LCD screens. I have a suspicion that that method was used for old SMPTE Standard Def 525 Interlace CRT screens. Progressive screens might not work, and HD displays might also not work. Finally, the orientation of the camera in relation to the display might compromise you results. What this is, is if the focal plane shutter travels in the same direction as the scan, e.g. from top to bottom. If you orient the camera in the opposite direction, where the FP shutter travels from bottom to top, it will be different.

Good explanation. I'll definitely not be using the television method.


If you do not have any equipment for testing, but have a DSLR, you can use the DSLR as a "digital back" for many cameras to test shutters. Keep the shutter you want to test open and get a couple of reference frames with the DSLR at different shutter times, then put the DSLR in bulb mode and take some shots using the shutter you want to test. Match brightness levels to find the real shutter speeds.

I would not want to test a lot of shutters using the above method though. Im not sure what the best way to do that would be, there seems to be major issues with most tests I have seen proposed. From what I understand many shutter testers test with only a single beam, which will not give accurate results for leaf shutters at high speeds, since there is a major difference when measuring the center of the shutter versus the edge, or even when measuring different spots at the same distance from the center. Still, it may be the only way to go for quick testing, and the results should be good for focal plane shutters.

I did the DSLR method tonight and I wasn't entirely satisfied. The results looked very promising (pretty much spot on throughout) but I would like a more exact way of measuring and comparing. This method of matching brightness levels and visually comparing histograms doesn't seem exact enough. I guess I just want to see some numbers haha.

Anyway, I think I might go and pick up a phototransistor tomorrow and rig an audio jack/phototransister shutter speed tester. About that, I've seen images of people connecting a 1.5V battery to the phototransistor and I've seen images where the phototransistor is connected directly to the audio cord and simply plugged into the computer. What is the reason for the battery and is it necessary to run the test? Will simply soldering a cut audio cord to the phototransistor work?