audio is never accurate, it isnt measuring the actual amount of light passing through at the moment the shutter opens. what you are timing is all the noise before n after the shutter opens n closes... as small as it may be, it can account for the overage.
The issue of using a waveform to test shutter time is discussed in post #7. To my mind, it's desirable to use an application that provides a detailed waveform display, and to keep in mind Bob Salomon's post #18.Originally Posted by Paul Ron
audio is not an accurate test for shutters. shutter testers measure the actual light passing through to the film.
audio testers measure noise no matter how good your app is... the sounds a shutter makes before n after the shutter opens n closes is what causes discrepancies in your speed times regardless of how nice your traces are. shutter testers should mrasure light, not sounds. film doesnt see sound!
if you want to time a shutter, buy a real shutter tester. they are cheap these days on flea bay.... or make one using a photo diode as seen on the internet diy projects.
That is pretty good for an old mechanical shutter. I usually count out 'one-one thousand, two-one-thousand' etc. when I test my shutters. Because after the 1 second mark, that is how I'm timing the exposure. I also listen for how smooth the escapement action sounds. If it sounds smooth, the shutter will more likely be precise. Accuracy is less important if one bases exposure on in-camera film testing.
Just to give an update. I went today and left it for CLA. The guy said, judging by the sound, it could work better, that mechanical shutters need to be used and that he will call me next week when it is done.
I'd have to partially amend one of Bob's previous comments. What I think he meant is that any new shutter PREDICTABLY firing in a tight range + - 30% from its official marking is acceptable. One just factors in the difference after measuring actual speeds at the respective settings. But any shutter only as good as + - 30% RANDOMLY, I'd personally set aside, at least for color work.
May as well add this question
In your experience do both Copal 0 and Copal 1 have similar life spans
or hours to rebuild
I have a choice coming up
anybody?
Tin Can
The other issue with audio testing is shutter efficiency... It takes time for the shutter to fully open, and is (very slighty) exposing before fully open... Granted this is a very small amount, but for the "speed freaks" this is another factor... And yes, this changes at different aperture settings... So a light reading TTL is needed for a true picture...
This subject was much covered in the 40's, as flashbulbs had their own peak, and shutters had to allow the bulb "burn" to start, then match the two peaks for highest efficiency of the bulb output... Books from that era had detailed descriptions of how the shutter operations worked... A good source to check would be the Morgan & Lester "Graphic & Graflex Photography" series yearbooks...
But in practice, this should not be an issue if speeds are consistent (for outdoor use)... But maybe more so in studio settings, but also when the exposures are done under bright continuous lights, lens is stopped down, the longer speeds are usually used, where the speed error factor is relaxed, and minor errors are diminished...
Shoot away!!!
Steve K
Update 2. Got it back from CLA, now 1sec is 1.1 (previously it wast 1.3).
As tested using an optical shutter tester with certified accuracy?
Bernice
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