Shutter speed iPhone app

Discussion in 'Miscellaneous Equipment' started by Mainecoonmaniac, Mar 1, 2013.

  1. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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    I have the Shutter Speed app for iPhone and I find it hard to use. Maybe someone can make an app that uses the camera that actually measures the shutter with the camera by measuring duration of the light instead of using the sound of the shutter?
     
  2. rawhead

    rawhead Subscriber

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    It's probably not very practical for higher speeds. In order for something like that to work, you'd need to be using the CMOS sensor in the iPhone in "video" mode, where it's constanly exposing and "waiting" for the light to hit the sensor. And since the frame rate for iPhone cam is 30fps, reallly the fastest shutter speed you can measure using that is 1/30s. I'm guessing that the Shutter Speed app you have can go faster than that?
     
  3. M Carter

    M Carter Member

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    I was thinking this over the other day - something like this would likely work with the slowest iphone "shutter" speed, and measure how much of the light is scanned. The iPhone has such a low scan rate for the sensor though (that's why you get "jello" when you move the phone - things like phone poles become slanted). I doubt the sensor is scanned fast enough to do faster shutter speeds.

    Ever slide a document around on a xerox machine or scanner bed while the light is moving across the glass? That's essentially what happens with digital sensors (they're moving much faster, but same effect).

    But the calculation would likely be based on "size" - how many rows of pixels get illuminated, divided by the sensor scan time. Which would likely change based on distance between the shutter and the phone's camera. My best guess anyway.
     
  4. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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    So many smart APUGers! So how useful is using sound sound from a clicking shutter to measure speed like the iPhone app?
     
  5. rawhead

    rawhead Subscriber

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    I've done shutter speed test using sound recorded with a microphone connected to a computer. It's pretty good up to 1/60s or so. Better option is this product: http://www.ebay.com/itm/Camera-shut...526?pt=LH_DefaultDomain_0&hash=item230a1554f6

    This actually uses a photodiode to detect the increase/decrease in the amount of light, THEN converts that into sound waves sent to the computer. With this I can measure up to 1/250s reliably, and pretty good at 1/500s. The specs say it can do 1/1000s, which I'm finding hard to do. Regardless, you really can't beat the price :D
     
  6. cliveh

    cliveh Subscriber

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    Wash your mouth out with soap and water.
     
  7. Andrew Simpson

    Andrew Simpson Member

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  8. E. von Hoegh

    E. von Hoegh Member

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    Not very, if you want any sort of accurate results. If you look at the trace of the audio signal on a 'scope, you can get useful information about the slower speeds - I was playing with this using a contact mike, a simple amplifier, and a 5" Tektronix 'scope back in the early 2000s and gave it up as useless & went back to a proper tester that measures the duration of the light.
    Think of it this way - what's the purpose of any shutter? OK, so why listen to it and try to interpret?
     
  9. Doremus Scudder

    Doremus Scudder Member

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    The shutter-speed app I have (Shutter Speed by Lukas Fritz; linked to above) works well on speeds up to 1/60th sec or so with sound. With the photo sensor available on eBay it should be accurate for higher speeds as well.

    In sound mode you measure the time between shutter opening and closing sound peaks. With the photo sensor, the actual light is measured. Neither of these take into account the slight drop in transmission from the shutter opening and closing at larger apertures, but neither do most shutter speed testers.

    I shoot at f/22 or smaller and at relatively slow speeds, so for me, the times I get with the app to be well within usable parameters.

    Best,

    Doremus
     
  10. Chan Tran

    Chan Tran Member

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    for most people speed slower than 1/60 is not often used as 1/60 is usually the lowest speed for hand holding of course it depends on focal length as well as how steady one is.