All throughout my career in photography I have shot in manual mode, except for the odd time when I wanted a certain aperture (i.e. I set aperture priority) and shutter speed was guaranteed to be adequate in the situation (outdoors in full daylight). Lately there have been a number of pro photographers posting about the benefits of auto ISO when paired with manual mode. I have to admit, I had never tried this, and the arguments for it in wildlife photography especially made sense, because in rapidly changing light, it is fast and accurate, far faster than fiddling with it manually when you are tracking a moving subject. So I set my camera to manual, but changed the ISO from a fixed value to AUTO, expecting to try a shoot outdoors in coming days.

Fast forward to a month later, I was setting up the above shot in my studio and took a test shot of the background to start. Checking the image, I was surprised to see that it was completely white. For about a full minute I was confused, wondering what was going on. Then I remembered – AUTO ISO was still on. These are the kinds of things which always seem to invariably pop up in photography, given the great number of options we now have in our modern cameras. Of course the image was white, as my studio strobes are entirely manual – the camera was not expecting flashes to go off. When the flashes triggered the image was entirely blown out to white.

If I had put a dedicated flash on the the camera shoe set to ETTL, or had off-camera flashes which were also set to ETTL and dedicated, there would have been no problem with AUTO ISO with the camera in an appropriate aperture and shutter speed for the situation. If these two settings are way off for the ambient lighting, even AUTO ISO working with ETTL flash cannot save you.

I realize I made a dumb mistake, hardly worth posting. But there may be a beginner out there somewhere who gets confused by this. Hope it helps!