Came across some curious Fuji X100 behaviour on the weekend, just thought I’d throw this out there to see if anyone had seen it too.  A bit hard to explain, so bear with me…

Saturday night, shooting a friend’s birthday party, turned off Auto ISO and changed to 6400ISO manually for that event.  (It was dark!)  Changed it back to Auto (highest setting 3200) at the end of the night.

Next day, out walking the neighbourhood in broad daylight, and kept finding the Auto ISO giving me hugely fast shutter speeds at f/16, and discovered the ISO was up at 3200.  In daylight, like the photo above, looking across Miramar to Stone St Studios - which was at 1/2000th @ f/16, and 3200ISO.  Huh?!

So…went back into the manual ISO menu (without turning Auto ISO off), turned that back down to 200, and…guess what.  The Auto ISO started choosing lower settings and giving me sensible choices of shutter speed - 1/60th at f/11, at 250ISO for example.

So my conclusion is this: auto ISO is somewhat influenced by the manual ISO setting you have the camera set on, even though you’re not using manual ISO.  If that’s up high, it assumes you’re wanting fast shutter speeds and ISO, rather than trying to give you the cleanest file possible by keeping the setting low.

Anyone else found this - or want to test my theory on their cameras?  Perhaps the new firmware (due out this week, allegedly) will simplify things - it would be so much better if Auto ISO was at the end of the ISO menu, rather than hidden in another settings menu entirely!