Is auto ISO fixed with fill flash?

Started 3 months ago | Questions thread
Bender79ita Contributing Member • Posts: 956
Re: Is auto ISO fixed with fill flash?

Jigal wrote:

Currently I'm mainly shooting pups in our living room using a bounce flash. I set the A6400 in P mode, the Godox TT685s to TTL and noticed that the photos were quite dark. Exposure compensation on both the flash and the camera didn't make any difference. The histograms showed that non of the graphs (white, red, green, blue) got further to the right than about two thirds of the way.

There is no reason to use P mode when using a dedicated flash. ISO and flash will adjust exposure for you.

Suddenly I noticed that all images had an ISO value of 200. I had set the auto ISO range to 100-400. Tonight I experimented a bit and each time the ISO was set to half the maximum value of that range (for all photos). I didn't change the lower limit, so maybe it sets a value half way between maximum and minimum.

Don't try and make sense of it, it'll drive you crazy.

I couldn't find anything in a manual about this but I'm really surprised by this. I kind of expected the camera to select the lowest possible ISO setting in the range that the light provided by the flash would allow.

That would mean using the flash at full power, which is rarely desired. Give it a boost of exposure with iso (400 or any above).

Is this the behaviour of the camera? Or is it influenced by this particular flash? (Should I look for the HVL-F60RM?)

Most cameras work very weird with auto iso and flash. I used this setup on Nikon too a couple times, never again.

Are there settings to make it automatically select a value inside the range?

Select the value yourself. Shoot manual exposure; 1/100 or so, desired aperture, iso400, ttl flash.

If you think it's too much flash, increase ISO. If you want more flash, decrease ISO.

Once you set the shutter speed and aperture, that's pretty much the only thing you have to control.

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