Monday, 12 January 2009

High ISO in Flash Photography

It is great to have the option to crank up the ISO when the light is getting low and still get usable images at 800, 1600 and even 3200 ISO the the D3, but have you thought of using higher ISOs when shooting flash? Using higher ISOs allows us to shoot with a smaller aperture to increase depth of field which is a no brainer. But another great advantage is to using higher ISOs to reduce flash recycle times. This is especially important when shooting with small battery powered strobes like Nikon's SB units. This means we need less light for a correct exposure and we can therefore dial down the power of the flash unit. If it takes 1 second to recycle the flash at full power we can shoot at 1 frame per second to get a flash lit exposure. If we up the ISO by 2 stops we can reduce the flash power to 1/4 power allowing us to get more than 4 frames per second. (We get more than 4 frames per second because the flash is recharging as soon as the first frame has been fired.) In the above sequence shot at 1/250 sec f.5.6 at ISO 400 I managed to fire off 11 frames at 8 frames per second before the flashes ran out of juice. And that is without external power packs (SD-8a or SD-9.) Not bad for a strobe that can fit in your pants pocket!

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