Measuring accuracy of camera time codes

From: George Roberts (
Date: Tue Jun 02 2009 - 18:27:02 UTC

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    For a digital camera - to accurately calibrate the actual time a camera puts in 
    the image file the solution is in essence to photograph a clock.
    The catch is you need to do this for long exposures because the digital camera 
    may do several operations (open shutter, expose, close shutter, possibly expose 
    a dark frame for possibly another several seconds, convert to jpeg, then write 
    to memory).
    So you need a type of clock that is accurate, that changes, but that is readable 
    on long exposures (like 1 or 2 seconds).  Ideally you want a clock that puts out 
    some kind of moving lit pattern on a black background similar to a brightly lit 
    second hand on a black background but hopefully much faster than a second hand.
    It is also interesting to take short exposures of a clock to see if there is a 
    delay in the time code related to jpeg conversion or something else.
    - George Roberts 
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