FEC vs power?

wadesworld

One thing about my SB-800 has me confused. Apologies if it's a noob question, but I didn't really see a discussion of it in the SB-800 manual.

I can set FEC or power (i.e. 1/132). Don't both serve to reduce the amount of light coming out of the flash?

If so, is it simply a matter where you'd manually set the power output if the flash were being used as a remote where it's not getting information from the camera but use FEC where information from the camera is available?

Tim Kamppinen

wadesworld wrote:

One thing about my SB-800 has me confused. Apologies if it's a noob question, but I didn't really see a discussion of it in the SB-800 manual.

I can set FEC or power (i.e. 1/132). Don't both serve to reduce the amount of light coming out of the flash?

If so, is it simply a matter where you'd manually set the power output if the flash were being used as a remote where it's not getting information from the camera but use FEC where information from the camera is available?

Flash exposure compensation allows you to modify what the camera thinks is the "right" flash power to get a good exposure. So if you shoot with FEC of 0 and your subject looks about a stop underexposed, you can bump the FEC up to +1 to compensate. If you're using the SB800 as a remote with the CLS system you can still shoot in ittl and use this feature just as if the flash was on camera. What happens is that the flash sends out a "monitor preflash" just before the actual exposure. The camera "reads" this flash to determine what power the SB should fire at, and then sends that firing data to the remote SB for the real exposure flash.

The difference between using manual mode and ittl with exposure compensation is that with the former method you can set the flash to any power you want, while the latter method only allows you to adjust up to +-3 stops from what the camera thinks is the correct power setting. The other difference is that in manual mode you'll have total consitency from shot to shot because the flash will stay at the same power setting, whereas in TTL mode if something changes, such as the ambient light or your composition of the shot, etc. the flash power may also change in order to get a "correct" exposure for the scene. Of course the bonus is that TTL might be right to begin with and then you don't have to mess around trying to get a good manual flash exposure.

Personally I only use TTL when I'm in situations where I need different outputs from shot to shot and I don't have time to adjust the flash settings, such as shooting an indoor event where I'm moving around and bouncing off of walls and ceilings. If I'm shooting a portrait that I have time to set up and dial everything in manually, then I do that becaue I know that I don't have to worry about the light changing from shot to shot.