Thanks for testing, I'm glad it worked. Including the speeds for older shutters is a good idea, will be part of the next update !
Unfortunately there will be no Android version, as I have no idea how to develop for that (it's very different from iOS).
@Diapositivo: I don't quite see your point, what has flash synchronization to do with the app ?
With shutter speeds faster than the X-synchro, as you know, the second curtain begins its trip before the first curtain ended its one, there never is a moment when the entire frame is exposed to light, the film is lighted by a "slit" of light moving along its length.
You seem to be aware of the problem but not of the fact that the last measurable speed with your app is the X-synchro speed.
Please consider that satisfying results from most SLR‘s as well as from cameras with focal-plane shutter can only be obtained up to the 1/125sec. Thereafter, the time is regulated by the distance of the slit between the two curtains, wich doesn‘t affect the shutter release sound very much and therefore can‘t be recognized in the waveform !
Could become, for the sake of clarity, and as a mere suggestion:
Please consider that satisfying results from most SLR‘s as well as from cameras with focal-plane shutter can only be obtained up to the the X-synchro shutter speed and including it, that is often 1/60 or 1/125sec but can be as low as 1/30th or as high as 1/250. Thereafter, the exposure time is regulated by the distance of the slit between the two curtains, which doesn‘t affect the shutter release sound very much and therefore can‘t be recognized in the waveform! The X-synchro speed can normally be recognised easily as it is marked by a "lightning" symbol or is painted with a different colour on the shutter speed dial. Some cameras have an X-synchro speed which is different from the normal sequence, e.g. 1/90. Refer to the instruction manual..
Central shutters (leaf shutters) can be used with flash on all speeds and can be used with your app on all speeds, I suppose.
X-synchro refers to electronic flashes. Some bulb flashes have a slow-combustion emission which allows the photographer to use faster speeds without side effects because the flash lasts long enough to hit the film during the entire "slit" travel. IIRC there are now some electronic flashes who work the same way and allow the use of a shutter speed faster than the X-synchro albeit with a lesser flash power.
Ah ok, now I understood what you mean, thanks for explaining.
You're right, this is a simple and elegant method to judge, up to which maximum speed the app can provide accurate results for a given camera. Haven't thought about this yet, I will add this to the website soon.
I actually don't think the X-sync thing is a problem, depending on what impulses you're lining up the time measurements with. There are four events:
1) first curtain travel starts
2) second curtain travel starts
3) first curtain travel completes
4) second curtain travel completes
Slower than X-sync, the ordering is 1, 3, 2, 4 and faster than X-sync, it's 1, 2, 3, 4. As long as you measure the timing offset between 1 and 2 or between 3 and 4, that's the shutter time. The travel time (1-3 and 2-4) is irrelevant to the exposure.
The above assumes that it's possible to make out these four distinct events of course, and that may not be possible depending on the shutter design. And it assumes that the user knows enough to select the correct pair of events, the ordering of which depends on the relationship between shutter speed and x-sync.
Great idea Lukas. Was about to download the app, but then remembered that my 3rd Gen iPod Touch doesn't have a microphone that I am aware of, so wonder if the compatible devices listed on iTunes might need to be updated?
Actually you can use this app on your iPod, if you have earphones with a built-in mic ! Just plug them in and voila, you have a microphone on your iPod :). Maybe I should mention this in the description.
I will try the circuit Ralph but I would use the oscilloscope for the measurement rather the sound card. My set up currently works quite well for manual camera but I can't test a camera on automatic. I am thinking that I can make a variable standard light source out of a dichroic enlarger head to simulate the light level than measure the shutter time to test an aperture priority camera.