Auto ISO with a Hot-Shoe Mounted Flash
The behaviour of the Auto ISO algorithm is consistent when using the camera pop-up flash in slow mode as well. Unfortunately, things are weirder when using a hot-shoe mounted flash, such as an SB-400. In this case, the camera increases the ISO sensitivity up to four times the value currently selected and won't raise it any more, even if you selected a greater maximum ISO.
As per the blog
The 1.01 firmware seems to fix this undocumented "feature": the Auto ISO behaviour is the same when using either the pop-up flash or a hot-shoe mounted flash.
However My 5100 (bought recently) has firmware 1.01 but it is still exhibiting the same problem. Has anyone else also faced this issue ?
#1. "RE: Auto ISO with a Hot-Shoe Mounted Flash" | In response to Reply # 0Leonard62 Nikonian since 15th Mar 2009Tue 19-Jun-12 03:07 PM
The bottom line is don't use Auto ISO with flash of any kind with the D5100 or D3200 for that matter.
The camera Auto ISO will raise the ISO value to match the darkened ambient light in the room. In the case of setting the high ISO point to 3200 or 6400 with the built in flash it could raise the ISO up to that point.
I just set my D5100 to Auto ISO with a high point of ISO 3200. I then took two identical photos.
With the built in flash ISO jumped to 3200. I had the default ISO set at 200.
With the SB400 flash mounted, Auto ISO set the ISO to 800. So the bloggers 4X number seems correct with the SB400.
Again. Don't use Auto ISO with flash.
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#2. "RE: Auto ISO with a Hot-Shoe Mounted Flash" | In response to Reply # 1
#3. "RE: Auto ISO with a Hot-Shoe Mounted Flash" | In response to Reply # 2jammike Registered since 19th Jun 2012Tue 19-Jun-12 03:29 PM
I got the impression from the Blog that this was a bug not a feature. Infact this is what prompted me to fix the Auto ISO Sensitivity settings. thanks for your input.