Drawing a Blank on 1D Mk III ISO Problem

At the moment I feel like an idiot. For the life of me I can't figure out why I can't set my ISO lower than 200. I'm sure I've got some custom function screwed up or something but I'm drawing a complete blank on what is going on here. I have this funny feeling it's going to come under camera operation 101, but what am I missing? Anyone have a suggestion?

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Turn off highlight tone priority.

Left Handed Brisket wrote in post #17915087
Turn off highlight tone priority.

+1

Left Handed Brisket wrote in post #17915087
Turn off highlight tone priority.

That did it, Thank you! Now I need to do a little studying on highlight tone priority. I don't know how/why that got changed.

Here's what the manual says:

Thank you. I actually went to the manual trying to find information on setting the ISO but I didn't run across that, at least not until after the help I received from you guys. Highlight tone priority is not something I've ever played around with, and to be honest, from what I read there I really don't see much advantage to using it. Your lightning fast responses amaze me though Thank you!

Glad to help. I've tried HTP a couple of times and although it is supposed to work on RAW files, I think that it is mostly for in-camera JPEGs. I couldn't tell much difference in the RAW files. Quite a price to pay, not being able to use ISO 100 or 12800, for not much gain.

rrblint wrote in post #17915113
Glad to help. I've tried HTP a couple of times and although it is supposed to work on RAW files, I think that it is mostly for in-camera JPEGs. I couldn't tell much difference in the RAW files. Quite a price to pay, not being able to use ISO 100 or 12800, for not much gain.

I agree. Obviously I haven't done any testing but that makes complete sense. I shoot everything at as low of an ISO as I can possibly manage so I absolutely don't want to give up ISO 100. And, I haven't shot JPEGs for years. It would actually be kind of nice if you could disable all of the custom functions you're pretty sure you'll never use.

I tried HTP when I first got my 60D. It is useful if/when the 'standard' exposure is acceptable. Maybe I'm weird, but that doesn't happen often the way I shoot. For me, HTP just got in the way when dialing in +/- EC. HTP seemed to always be trying to correct my corrections. I don't use it.

Bassat wrote in post #17918859
I tried HTP when I first got my 60D. It is useful if/when the 'standard' exposure is acceptable. Maybe I'm weird, but that doesn't happen often the way I shoot. For me, HTP just got in the way when dialing in +/- EC. HTP seemed to always be trying to correct my corrections. I don't use it.

That makes sense. I frequently shoot outside of the "ideal" exposure also. Thanks!

From what I understand the reason you cannot select ISO 100 in HTP is that it uses ISO 200 settings but sets the analogue gain for ISO 100. Effectivly exposing to the left, not something most people would recomend doing with a Canon sensor. I guess it's useful if you are not careful about your exposures and want to avoid blowing highlights. Personally I would rather meter with care, and use ETTR to maximise the exposure to reduce noise in the shadows. Especially when shooting 3D backlit subjects where I need to maximise detail in both the shadowed side of the subject, and retain detail in the highlights. This can be tricky when there are six or maybe even seven stops of difference to deal with.

Alan