doug Nelson |
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Adjust Flash Output for Higher Camera Synch Speed?
My cameras have always had a flash synchronization of 1/60 sec, like my Canon F-1 (early). The Canon T90 syncs at 1/250 sec. If I'm cutting the light input to my film two stops by using a faster shutter, do I adjust the aperture recommendation on the flash's scale by two more stops (open up two) to compensate? Or is the flash scale recommendation based on camera-to-subject distance valid regardless of the camera's synch speed? Sorry if it's a dumb question; synch speeds of cameras vary. I've never read instructions on a flash that said the scale was valid only for 1/60 synch speeds.
November 07, 2002
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Jeff S. Kennedy |
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No. As long as your shutter speed is at or below the sync speed it is irrelevent to exposure. This is because the duration of the flash is much shorter than 1/250th of a second. It doesn't matter what your shutter speed is because the duration of your flash, in essence, becomes your shutter speed.
November 07, 2002
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Jon Close |
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Ditto what Jeff K. stated. At the same aperture, the faster shutter speed will affect ambient light only (make the background darker) compared to a slower shutter speed. The flash exposure of the near subject is unaffected.
November 07, 2002
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Jon Close |
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PS. The advantage of the higher sync speed is in outdoor or bright light fill-flash situations. You have more control over depth of field with the higher sync speed. If you are using fill-flash outdoors, you might have an exposure of 1/60 and f/16. With the higher sync speed you can choose 1/125 & f/11, or 1/250 & f/8.
November 07, 2002
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doug Nelson |
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Thanks, guys, for a very clear and thorough explanation.
November 07, 2002
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