I have purchased the new 5d mk iii. which arrived today and have been testing it performance, especially the manual mode as thats what I shoot with the most. I hoped there would be an auto ISO setting for manual, which there is BUTWhen i put my 1DM3 in manual the meter in the window on top doesnt even show up because yea its manual if you swing your aperture way high or way low it will drop to over or under expose based on the range of your iso selection. The bigger the range of auto iso the more you will see the meter dead center. It actually works like a charm. Still it would be nioce like on your cam you can set the flash to always expose a third over. Of course i'd love that option even for manual. Maybe they could make the iso higher when you want a third over...hmmm
why cannot I set an exposure compensation while in Manual mode with auto ISO?
I always use manual mode to control shutter and aperture. I meter my exposures from my client's faces that are usually set at +1EV to accommodate light skin. Auto ISO would allow me to keep up with rapidly moving children as ISO speed is not so critical as shutter and aperture setting for me. I appreciate the new advantage of auto ISO that the mark ii did not have, but now my exposures will be a full stop under-exposed using the advantages of auto ISO with the mark iii
Flash and auto iso is not a good mix
Test it out, i was curious last night in a drak room and without flash i had to use like 56,000 iso but with flash it dropped down to 400 iso in auto iso setting.