SB900 settings questions ISO on flash

Mike Daly

New member
I am wondering if someone could exlplain the ISO function of the flash. It can be changed in the flash settings. I understand it as a whole with the camera. I use the flash in manual mode for high school basketball off camera with remote trigger.
Does changing the ISO on the flash (not camera) make a differance in power output of flash. The ISO can be changed from 20 to 8000.

Thanks for your help and replies
 

WayneF

Senior Member
I am wondering if someone could exlplain the ISO function of the flash. It can be changed in the flash settings. I understand it as a whole with the camera. I use the flash in manual mode for high school basketball off camera with remote trigger.
Does changing the ISO on the flash (not camera) make a differance in power output of flash. The ISO can be changed from 20 to 8000.

Thanks for your help and replies

Generally no, not important (with exception). Setting ISO and fstop on the flash does not matter to the flash in most flash modes (M, TTL, etc).
Setting ISO and fstop are only important to the flash in the A and GN modes, when the flash itself has to compute an exposure and power level, and needs to know that information to do it. However, even then, the hot shoe flash gets ISO and fstop directly from the hot shoe, so it already knows, if connected.

It is only when the flash is off camera, then we need to set ISO and fstop then (and only for A and GN modes).

The big difference in A and AA mode is that A mode is only if off camera and needs to know ISO and fstop, whereas if on camera, the mode is instead AA, and already knows. Menu only shows one or the other.

The rest of the time and other modes, it is the camera metering that computes a power level (TTL Modes), or we set power level directly in M mode. Then camera ISO and fstop are shown, but just for information.... the power is as already directed.
 
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