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Flash Sync Speed For Digital Camera


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#1 Guest_David Lau_*

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Posted 28 April 2004 - 03:08 PM

I learnt that non-SLR type digital cameras actually have no mechanical shutter, and therefore can sync with external flash at all shutter speeds, up to the highest such as 1/2000 sec. Also, the amount of light from the flash striking the CCD sensor is about the same regardless of shutter speed, as the flash duration of most electronic flashes are very short, less than 1/2000 sec.

Is this true? Can anyone share experience in using flash with high shutter speed? To be able to sync with high shutter speed is very useful for fill flash in bright daylight, as one can use a larger aperature to blur the background.

#2 Herve

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Posted 24 May 2004 - 09:41 AM

Quite interesting question blink.gif

I have an Olympus C-4000 Zoom (with an external flash connection) and a old Braun flash dating from the eighties (guide number is 40). Thanks to 4 AA batteries it always work wink.gif

The flash doc's says the longest flash duration is 1/300 sec at full power.
A shorter flash means less light. The amount of light is settled by the flash duration. So a small flash is a quick flash (maybe less than 1/2000 sec).

The Olympus doc's says the best synch is lower than 1/300 sec.

I'am using the flash in automatic mode with a constant aperture. This mean that the C-4000 is in manual mode with the aperture set the same as the flash (usually f4) and a fixed speed of 1/160 sec.

Using these settings I've no problem of synchronization.

About your question, I thing that the C-4000 has a mechanical shutter (you can hear a very small clic when shooting). So I don't thing I can synchronize at 1/1000 sec. I will try to see if it works with a full power flash. It will be done at no cost (or, anyway, please Donate $ or €... rolleyes.gif )

Oh, BTW, the C-4000 has also a internal flash that is fully automated with all modes (I just tell I force a fill-in flash and he does it). I am quite sure that at this time the synch speed is around 1/100 sec. I will try a forced fill-in in very brigth condition...

Regards,

#3 Herve

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Posted 25 May 2004 - 08:53 AM

I've made some test that can be seen at:
http://www.photograp...&cat=500&page=1

As you can see, at full power, first row, I loose some brigthness each time I increase the synch speed (The number in the corner is the average RGB value seen in photoshop). The more I loose is between 1/500s and 1/1000: 28 RGB lost. I think I'am out of sync there. Flash has surely a speed around the 1/500s.

Second row, is taken with the external flash at a quarter of his power so let's say at 1/1200 sec. As you can see, no change in the available light even at 1/1000sec.

Last row is the build in flash (I've no info on the speed of that one).
As you can see, they are variation but the 1/1000s value is nearly the same as the 1/60s value. So synch is OK.

So thanks for the test you forced me to do (don't forget do donate $€...) !

I know that I can use the build-in flash at any speed and that the external flash is to be used at speed lower than 1/500s.

It takes me around 30 minutes to make these tests but now I am a lot more confident with the use of my flashes.



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