iso and onboard flash

In the past, as far as I ever noticed, the ISO remained constant, matching my non-auto setting (generally 100) when shooting with the flash. Today when shooting some macros, the iso is jumping up to 800 at f32 using manual flash/full power. I looked in the manual and didn't see anything indicating that this was supposed happen when in auto iso. Has this changed from the 5200, were it always shot at the set iso?

Auto ISO is determined only according to the ambient. The flash merely reacts to whatever the ISO it discovers to be in effect, and the TTL part tries to match the flash power to the scene that way.

Auto ISO value is not about the flash. Auto ISO is about only the ambient. My notion is the only thing that could have changed is the ambient level present. Or the f/32 effect on the ambient might be new.
If it is not doing what you want, you can turn Auto ISO off.

There are other model differences though, regarding Auto ISO.

Older DSLR models, up through the D300 would not let Auto ISO increase at all if it detected we were using flash. Because, we were using flash instead.

Then Nikon got the bright idea to change that, and starting with the D300S, Auto ISO would fully increase according to the ambient, and if Auto ISO, the flash generally always had to work into the highest Auto ISO.

But then they learned again, and starting with the D800, now Auto ISO is only allowed to increase two stops (typically to ISO 400) if flash was discovered present. ISO 400 is generally good with bounce.

Two exceptions ...

That is speaking of external hot shoe flash. The internal flash does not limit Auto ISO, and will still let the ambient go to very high ISO (according to ambient). Auto ISO value is still not about the flash however, it is determined by the ambient, at whatever aperture and shutter speed. Flash is not affected by shutter speed, so you could lower shutter speed to help the ambient, and then see lower ISO. But the best thing with the most control is to turn Auto ISO off with flash.

And another exception to all above is that if the flash itself is in manual flash mode, Auto ISO will never increase. Manual flash cannot react to ISO changes. TTL does react with power level changes.

Discovered the problem after reading your reply -- I had somehow switched to TTL mode, which I never use.

Thanks for the information

When you are in auto iso say 200-6400 the camera automatically ups the iso to (4x the base iso ) 800 iso when you turn the flash on . This is not in the manual but is Nikons reply to Canon

Love Nikon said:

When you are in auto iso say 200-6400 the camera automatically ups the iso to (4x the base iso ) 800 iso when you turn the flash on . This is not in the manual but is Nikons reply to Canon

Click to expand...

A few details though... Only on the most recent few camera modes models (D800 and later), the camera LIMITS Auto ISO to two stops increase (4x, typically from ISO 100 to ISO 400) if the flash is present, but only for external hot shoe flashes. The internal flash does not limit ISO that way (it is small and ISO can help it).

Auto ISO will not increase at all if the ambient is bright enough to not need it. Auto ISO is purely about the ambient. Reach up and turn the flash off (shut the internal door), and Auto ISO value will not be affected (except for hot shoe flashes, when this two stop limit is removed).

The many models from D300S until D800 did not limit Auto ISO. Then any time we are in dim ambient, Auto ISO goes sky high, and the flash has to use whatever ISO it discovers is in effect. The problem with that is when indoors, now high ISO sees the ambient well, but incandescent ambient is very orange. We need CTO filters on the flash to make it orange too, so we can use incandescent white balance. Few bother however. If using flash, it is better to keep ISO low, to keep out the orange ambient.

D7100 too ...I shoot thousands of photos every week using base iso at 200 and hence flash at 800 without any problems/filters /use of brain etc