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05-31-2011, 04:27 PM   #1
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vivitar 283 have enough to overpower sunlight?

I have a buddy who is going to sell me an old 283 and I was wondering if it has enough power when put in a 24" softbox to overpower direct sunlight?

thanks

05-31-2011, 04:52 PM   #2
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It depends....

I think the GN of the 283 is 120 (ft, ISO 100).

In direct sunlight, a proper exposure at ISO 100 is F/16 at 1/125 sec, or F/13 at 1/180 sec.

Let's use 1/180 sec. max sync. speed.

For the 283, at F/13 and ISO 100, the distance is 120/13 = 9 ft. That is for lighting ratio 1:1.

If you want ratio 1:2 (flash is for fill-in, 1/2 strength of sunlight), the distance is 9 * 1.4 = 12.6 ft.

If you add the softbox, which eats up light from the 283, the distance is much less than calculated above. If the softbox eats up 2 stops, you'll have to halve the distance (e.g. 4.5 ft for 1:1 lighting ratio).
05-31-2011, 05:21 PM   #3
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QuoteOriginally posted by SOldBear Quote
It depends....

I think the GN of the 283 is 120 (ft, ISO 100).

In direct sunlight, a proper exposure at ISO 100 is F/16 at 1/125 sec, or F/13 at 1/180 sec.

Let's use 1/180 sec. max sync. speed.

For the 283, at F/13 and ISO 100, the distance is 120/13 = 9 ft. That is for lighting ratio 1:1.

If you want ratio 1:2 (flash is for fill-in, 1/2 strength of sunlight), the distance is 9 * 1.4 = 12.6 ft.

If you add the softbox, which eats up light from the 283, the distance is much less than calculated above. If the softbox eats up 2 stops, you'll have to halve the distance (e.g. 4.5 ft for 1:1 lighting ratio).
that is great information and thank you!
sounds like it might be o.k on an overcast day, hopefully the wedding coming up will be that way,,,
btw, if I could find a way of using 2 283's in the softbox, would that double the distance or would I be able to use 2 at 1/2 power to equal one at full power so it will recycle faster?

thanks again
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