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08/01/2005 06:01:48 AM · #1 |
| How do I know the time my internal flash is fired in a shot?. I took a shot of a machining process, and I freeze the flying chips with the aid of the flash. Now, I would like to know the rate of these chips aproximately (chips per second). I search in the manual and the internet, but only aproximate numbers: 1/800, 1/1000, 1/50000 |
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08/01/2005 07:13:21 AM · #2 |
It depends...
I know that dosn't help, but, if you'll bear with me.
When your internal flash fires it does a 'pre flash' and measures the bounced light, and that sets the duration of the second brighter 'exposure' flash.
So it's possible that at it's 'lowest' setting it might be the 1/50000 and at it's brightest it's 1/800th.
With flash photography the flash (light) is pretty much constant, but the duration of the flash is varied.. (This is not true of complex studio strobes, but go with me on this one...)
Cheers, Chris H.
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08/01/2005 07:26:58 AM · #3 |
i will disagree with you Chris...
all flashes have an attack & decay aka rising slope & falling slope
and the shape of flash tends to be triangular (quick rise, long decay) not constant
measuring a flash output shape is simple
see Sams Flash FAQ down near "Strobe Light Output Test Circuit"
long decay gives you streaks like seen in  |
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08/01/2005 04:07:55 PM · #4 |
Originally posted by ralphnev:
i will disagree with you Chris...
all flashes have an attack & decay aka rising slope & falling slope
and the shape of flash tends to be triangular (quick rise, long decay) not constant
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True... I wus answering the question though. :-).
Although if we're gonna be picky it's not all that triangular, the energy in the tube rises on a sqaure law curve, the inverse of a cap discharge curve (odd that) and the decay is defined by the type of quench the flash circuit uses, and the characterisitcs of the tube. Mostly linear, but some are logrithmic.
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