New question about Nikon fill flash


Senior Member
I never do very well with responses to questions about flash actions. But I will try again. It seems a good thing to realize how the system works.

The situation. When using TTL fill flash, we set -1 EV or -2 EV flash compensation, and it becomes point&shoot. But the camera automation (for example camera A mode) has already metered the ambient, and has set the camera settings for ambient. So this means that since the camera has metered for ambient already, so adding any fill flash will overexpose the subject, perhaps by 1/3 or 2/3 stop.

I notice when my D800 in A mode, when on a tripod in constant light so that nothing can change when I reach up and turn on my speedlight, the metered shutter speed will increase about 1/3 stop. My notion is this is intentional to minimize that degree of overexposure when adding fill flash.

My older D300 model does NOT do this increase (when flash is turned on). The D800 always does.

There is a calculator for this at Flash pictures are Double Exposures- Outdoors but it assumes no shutter speed increase when turning flash on.

Problems: There are ifs and buts, but...
The camera will honor a Minimum shutter speed with flash (probably 1/60 second minimum).
The camera will honor a Maximum shutter sync speed (probably near 1/200 second maximum)
So those changes will occur, so it seems good to start with a shutter speed already avoiding those two limits with flash, maybe about 1/100 to 1/125 second...

I fear Auto ISO (and its minimum shutter speed) can only be a confusion about this, but was interested in hearing comments about how other models reacted to this? (slightly increasing metered shutter speed when adding flash, when there was absolutely no other change).

Oops, sorry, but I think I was wrong about this D800 shutter speed increase with flash.
I think Auto ISO was fooling me, and I cannot repeat it now.
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