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Using Flash Beyond The Guide Number Distance.

 
 
AustinMN
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      02-02-2007
On Feb 2, 1:39 pm, "Pat" <(E-Mail Removed)> wrote:
<snip>
>
> Another option, but quite a bit more expensive, is to hide a few
> flashed around the image to light up what you want. Your flash can be
> used as a master to fire either dedicated to dumb slaves that are down
> near your subject.


One combination I have used is a tripod and manual flash. With any
exposure longer than the flash recycle time, you can fire the flash
twice. With even longer exposures, you can fire the flash many
times. Keep in mind that you have to fire the flash (at full power)
four times to double the distance. I've even been known (in my
younger days) to run to a new location while the flash was recycling.

The technique works OK, (not really well) because noise still
accumulates with the long exposure.

Austin

 
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Morton Linder
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      02-03-2007
Mardon wrote:
> At 105mm & ISO100 my Canon Speedlite 580EX has a guide number of 58
> (meters). At ISO3200 (maximum ISO of the Canon 20D) the 'effective' guide
> number becomes 328. My lens has a maximum aperture of f/2.8. This
> indicates that in darkness, the maximum distance from the flash, at ISO3200
> and f/2.8, is 117 meters for a 'properly' exposed photo. My question is
> how far beyond this distance is a flash useful at night? The other night I
> photographed a piece of snow removal equipment at 200 meters, f/2.8,
> ISO3200, but it was badly underexposed. Even though the equipment was
> still well beyond the guide number distance of my 580EX, would the use of
> my flash have helped?.
>
> Related question for the 'oldies'. I seem to recall that the large
> flashbulbs I used back in the '60s really packed a wallop. I can't recall
> the guide numbers of those things. Does anyone know? I suspect they were
> well over 100 at ISO100 (expressed in the equivalent ASA in those days,of
> course.)
>


Tripod, beanbag, or use self-timer to trip shutter with least camera shake.

Morton
 
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