Cannot lower ISO below 200 MKIII

I have gone into CF 1-3 but no matter what I do I can not set it to 100 or 50. Followed the trusty manual to no avail. Maybe I am missing something here

Is Highlight Tone Priority on? Try turning it off...

Have you disabled the Highlight Priority? Memory seems to indicate that limits the ISO to 200.

talbot_sunbeam wrote in post #13752608
Is Highlight Tone Priority on? Try turning it off...

huntersdad wrote in post #13752610
Have you disabled the Highlight Priority? Memory seems to indicate that limits the ISO to 200.

Thanks guys for the quick response that was it !

And here I thought I knew it all.

Yep, if HP is on the minimum ISO is 200. Look at the top dial where it shows ISO and if it looks like this 2oo instead of 200, then you know HP is on.

Presumably this behaviour is because, with HTP on, the camera is underexposing the shot (to protect the highlights) and I assume that basically what it's doing is setting the ISO to one stop below what it "should" be.

As 100 is the lowest ISO on most camera, the camera couldn't underexpose until the shot is taken at 200 or higher - hence the camera artificially limiting the low end to 200...

ISO50 seems to be a special case which most Canon cameras don't have. Is it a "real" 50 or a fake one..? Otherwise there would seem no need to limit the 1DIII to 200 with HTP on - or maybe the software guys are just lazy and didn't want to change the HTP code they use for the other cameras...