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View Full Version : Testing Leaf Shutter with an iPhone?



Drew Bedo
20-Mar-2012, 09:23
I am an e-idiot (and maybe an i-idiot too). with that said: Is there a way to use an iphone or ipad to test the adduracy of a leaf shutter lens?

I would hope that there is some way that reads out directly in fractional shutter speeds, or even miliseconds.

Anybody know how or have any ideas on this?

vinny
20-Mar-2012, 09:37
On a computer u can use Audacity. I'm sure there's a similar app out there.

unixrevolution
25-Mar-2012, 21:49
Using Audacity and a microphone to test the accuracy of the low speeds might work, but I think above 1/30s you'll have trouble getting an accurate sounding of the exact open/close point. I could be wrong, but I don't see it being that accurate, as I can't really tell by ear a 1/400 from a 1/100.

Also, testing with an iPhone may work with the low speeds, but again, at 30 FPS, the highest speed you could possibly be sure of is 1/30.

There's a document here about testing leaf shutters with a CRT TV....

http://people.rit.edu/andpph/text-shutter.html

Additionally I could suggest loading up some instant film, getting an accurate reading of a controllable luminance value (IE indoors, light on a wall) and testing your shutter by checking the exposures that it produces rather than trying to directly measure the speed.

unixrevolution
26-Mar-2012, 04:12
After a bit of searching, the "Audacity" test seems reliable even up to the high speeds. I'll have to give that a try myself.

Here's another method:

http://www.graflex.org/helpboard/viewtopic.php?p=34429&sid=7e7ad0b3c7a09563b2eb3189fc64d7e4

Drew Bedo
26-Mar-2012, 10:35
Hello everyone,

I am new to this issue and not an electronic DIY guy. I have a passing understanding of current, resistance and so on, but don't really understand circuts or how the various components interact.

With all that said: I am interested in the concept of using a light sensor to generate an audio signal and analysing it with a computer. Having read this thread and some of the links: Does it work as a practical matter?m Is there a definative set of directions for the hardware?

unixrevolution
26-Mar-2012, 18:42
I can try making one this next week and let you know. If it works, I'll let you borrow my rig from me, or build one for you.

Tim Meisburger
26-Mar-2012, 19:49
Why couldn't you video the shutter opening and closing and then in a video editing program measure the time light is present? I'm not too familiar with video editing, but seem to recall you could measure scenes in fractions of a second?

unixrevolution
26-Mar-2012, 19:57
Why couldn't you video the shutter opening and closing and then in a video editing program measure the time light is present? I'm not too familiar with video editing, but seem to recall you could measure scenes in fractions of a second?

Most video cameras record at 24 or 30 frames per second, so above 1/30s its not a reliable way to time a shutter. To do truly reliable timing of shutters with video, youd need a framerate of at LEAST 500fps, and these high-speed video cameras are NOT cheap.

Tim Meisburger
26-Mar-2012, 20:06
Okay. That explains it. It that a hardware rate or software rate? Could you write a program that would instruct the camera to video at a higher rate, or is the rate determined by hardware.

Sorry if these are stupid questions, but in this area I am uneducated.

MMELVIS
26-Mar-2012, 20:22
Not using an iphone but it may work for you http://rick_oleson.tripod.com/index-135.html

Drew Bedo
27-Mar-2012, 08:44
Erik: Thanks, that would be great. Contact me through my website.