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Thread: Measuring your shutter speed without any new equipment

  1. #1

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    Measuring your shutter speed without any new equipment

    I think that I might have found a way to measure the speed of a LF lens shutter without buying any equipment ( if you already own a digital slr). I tested it and it worked for me. I am submitting here for your review.

    - Have a controlled light source.

    - With your large format point to a fixed object lit by the controlled light.

    - Open the LF shutter and leave it open

    - put the digital camera inside the LF and shoot through the LF shutter and lens at 1/10th, 1/20th, 1/30th, 1/60th. You will see a round light spot. If you are measuring for a speed of 1/30th for example, make sure that at this speed, the light spot is greyish ( not too bright)

    - Then close the LF shutter, put the digital camera in B and open it, trigger the shutter of the large frame.

    The picture taken should be matched to the pictures taken with the digital camera speed.

    So if the picture of the spot timed by the LF shutter most closely resembles the 1/20th speed of the digital camera shutter then your LF shutter is at about 1/20th. you can do the compare directly from your digital SLR lcd screen.

    This is how I confirmed that my Packard shutter is shooting at 1/10th not 1/25th as it should ;(

    I think that this method should be more accurate than anything based on sound because it measures the actual total light that goes through the shutter. It also takes minutes. Finally, no need for a computer so it can be done on the road.

    Let me know your thoughts or if this is not clear enough.

    Best Regards,
    Karl

  2. #2
    Japan Exposures
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    Re: Measuring your shutter speed without any new equipment

    This is great, thanks for sharing the idea.

  3. #3

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    Re: Measuring your shutter speed without any new equipment

    How do you know your DSLR shutter speed is accurate? To be considered accurate a shutter speed can be ±30% of the marked speed.

  4. #4

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    Re: Measuring your shutter speed without any new equipment

    Hi Bob,

    I knew that this question would come up so thanks for giving me the chance to answer it. The electronic shutter of a modern digital DSLR is partialy based on mechanics but mainly based on electronic timing and is typically extremely accurate. Certainly more accurate than I would ever need for my LF.

    Best,
    Karl

  5. #5
    Japan Exposures
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    Re: Measuring your shutter speed without any new equipment

    Does anyone really think that in 2009 a DSLR's shutter speeds would be inaccurate? Quartz timing etc have been around for 20-30 years now, infinitely more accurate than the mechanical stuff (not that it has to be super precise anyway, see Leicas).

  6. #6

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    Re: Measuring your shutter speed without any new equipment

    Quote Originally Posted by Dirk Rösler View Post
    Does anyone really think that in 2009 a DSLR's shutter speeds would be inaccurate? Quartz timing etc have been around for 20-30 years now, infinitely more accurate than the mechanical stuff (not that it has to be super precise anyway, see Leicas).
    Electronically timed and actuated but carried out mechanically by that shutter mechanism. Still can be ±30%.

  7. #7
    Steaphany's Avatar
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    Re: Measuring your shutter speed without any new equipment

    A method I've used years ago was shooting a frame from the screen of an analog Television. This method works for anything faster than 1/30th. The video is interlaced so two scans make up a complete image.

    If your test shot is between 1/60th and 1/30th you'll see an image across the whole screen, but part will be brighter than the rest which is where the second field is being captured.

    If your test shot is less than 1/60th you will only capture part of the screen with an image.

    To determine shutter speed, compare the vertical image size to the total screen height.

    A 1/100th shutter would capture an image that covers 60% of the screens vertical
    A 1/125th shutter = 48%
    A 1/250th shutter = 24%
    A 1/500th shutter = 12%

    A 1/50th shutter = 120% - a Full Screen image with 20% showing the brighter interlaced area

    To calculate the screen image percentage that a shutter speed corresponds to use:

    100 * ( Shutter Speed ) / ( 1 / 60 )

    Where Shutter Speed is the actual fractional time, i.e. 1/100, 1/125, etc.

    A note, I haven't tried this with a new digital TV.

    As an alternative, if you have or know someone with an oscilloscope, shoot a test image of the scope screen as a sweep of the screen is made. Here you can control the speed for very slow shutters, less than 1/30th, and knowing the time base of the scope, you'll be able to read the shutter speed right off the test image.

  8. #8
    hacker extraordinaire
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    Re: Measuring your shutter speed without any new equipment

    Electronically timed and actuated but carried out mechanically by that shutter mechanism.
    I think if you understood the mechanism of most dual-curtain FP shutters you would agree that the shutter speed is entirely under control of the electronics, actually. The first curtain is released, an electronically determined amount of time is allowed to pass, and then the second curtain is released. A variable or malfunctioning shutter mechanism will generally cause uneven exposure, not evenly slow or fast exposure. And since digital has less latitude than color negative film, if the digital cameras is working at all the shutter must be within spec.

  9. #9

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    Re: Measuring your shutter speed without any new equipment

    Quote Originally Posted by BetterSense View Post
    I think if you understood the mechanism of most dual-curtain FP shutters you would agree that the shutter speed is entirely under control of the electronics, actually. The first curtain is released, an electronically determined amount of time is allowed to pass, and then the second curtain is released. A variable or malfunctioning shutter mechanism will generally cause uneven exposure, not evenly slow or fast exposure. And since digital has less latitude than color negative film, if the digital cameras is working at all the shutter must be within spec.
    Interesting theory. Tell that to my oh-so-slow Ilex electronic shutter. Its timer energizes a solenoid to open it, after a predetermined interval has passed turns the power off and a spring closes it. Can't possibly go wrong, but it does, and consistently.

    Interesting theory. Tell that to my former F135s' solenoid-actuated shutters. One solenoid to open, another opposing one to close. Bang! Bang! All it takes is a sticky solenoid.

    Interesting theory. Timing circuits can be off, curtains or metal blades (think Copal Square Shutter and descendants) can move more slowly than expected, springs can be weak, solenoids/magnets can be sticky.

    Many are the ways in which an electronically timed shutter can go wrong. Not that clockwork is necessarily any better, even in the cine cameras (and a few 70 mm aerial cameras too) whose shutters just go round and round.

  10. #10

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    Re: Measuring your shutter speed without any new equipment

    I use my digital video camera for measuring 1/30 or longer times. This camera takes a digital video at a speed of 30 frames/second. I first record the shutter opening and closing, and than watch the video with a simple video editor software that will let you go forward one frame at a time.

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