 Sheryl L. Bowman |
Setting fill flash for outdoor shots I know to set my flash to one stop less than the available light for an outdoor shot. So at f 5.6, 1/125 sec., I'd set the flash for f4. BUT, if I changed the settings to f 11, 1/30 second, do I need to increase the flash to f8, even tho the overall exposure is the same and if so, why?
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Jon Close |
From your other questions, I gather you're using the Canon 550EX speedlight with an EOS 10D. If so, you do not need to make any adjustment for using the speedlight for outdoor fill flash. Canon's E-TTL and TTL algorithms already incorporate flash exposure reduction for that situation. If you have set Custom Function 14 to disable auto reduction, then you can dial in your own fill flash reduction by setting -1 or so stops of flash exposure compensation, either on the camera or on the speedlight (the speedlight settings will override the camera settings). If you are using a non-dedicated non-TTL speedlight, then you do as you stated above: set the lens for 1 or 2 stops smaller aperture than what the flash is set for.
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Sheryl L. Bowman |
In the past I've used Mamiya 645 and an off camera flash unit, set 1 stop less than the aperture on the camera. When I'm doing large groups with smaller apertures tho, I'm not understanding why the flash power would need to be higher when the overall exposure is the same (made up in the shutter speed). It seems like setting flash based on EV might make more sense. I have yet to fully test the 10D and 550EX on outdoor portraiture.
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Jon Close |
>>"When I'm doing large groups with smaller apertures tho, I'm not understanding why the flash power would need to be higher when the overall exposure is the same (made up in the shutter speed)."<< Smaller aperture is offset by longer shutter speed for the ambient/background exposure only. The flash exposure is simply reduced by the smaller aperture. Because the flash duration is only 1/500 to 1/10,000 second, you do not get more flash exposure with a slower shutter speed.
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