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Old Aug 22, 2003, 7:51 PM   #21
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Mathilde uP: Try this one - the best there is:

http://www.virtualdub.org/index
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Old Aug 22, 2003, 8:56 PM   #22
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Quote:
Originally Posted by voxmagna
If your camera has video or continuous shooting modes, point it at a TV set and then check through the saved file a frame at a time.

Sooner or later you'll find the black frame blanking black bar on your images.
?? Since most digicams shoot at 15fps (maybe 30fps) each frame should cover several cycles at 100 (or 120) peaks of AC ??

What am I missing here?
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Old Aug 22, 2003, 9:27 PM   #23
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Quote:
Originally Posted by BillDrew
[?? Since most digicams shoot at 15fps (maybe 30fps) each frame should cover several cycles at 100 (or 120) peaks of AC ??
What am I missing here?
There's also an effective shutter speed within each frame that's a lot shorter than the frame rate.
On my Video8 camcorder it's easily seen by 'filming' a TV screen, while cycling through the various 'modes' - normal, sports, night time, etc = and seeing what proportion of the TV screen appears light and what proportion dark.
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Old Aug 22, 2003, 9:43 PM   #24
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Virtualdub is indeed a marvelous and feather light program, thanks for the tip.

BillDrew I think you are right. Back to Hertz, and technical matters; 1 Herz is = 1 event per second. For example local power supplier delivers voltage at 50 Hz, thus 50 peaks in wave per second. The voltage in the wires alternates one is low when the other wire is at heigh, however when both are mid of their wave it causes a dip in current flow. However it could also be possible that I caught a small brown out on photo.

The monitor at 40 cm away could also have impact;
Monitor is 70 Hz and movie is 15 fps . 70 flickerings per second recorded at 15 frames per second = 4,33 flickerings per frame..
I should have done this arithmetic before I shoot the movie, luckily no film was wasted :-)
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Old Aug 22, 2003, 9:48 PM   #25
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Quote:
Originally Posted by Mathilde uP
local power supplier delivers voltage at 50 Hz, thus 50 peaks in wave per second.
100, actually, half positive, half negative, but both active in most applications.
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Old Aug 23, 2003, 5:56 AM   #26
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True, I was refering to peak in wave as literal highest positive point in voltage, your description is more complete.
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