50D doesn't go under 200 ISO?
 

I know this sounds silly but for some reason on my dad's new 50D I was unable to pick 100 ISO manually on AV mode, using the 24-70L lens. Lowest available was 200.

Friend of mine using the EOS 50D as well said he had no problem picking 100, any idea what might cause the issue? Could the lens be restrictive? http://www.discussworldissues.com/fo...ies/wacko1.gif

Just check see if you got Auto ISO on in the menu as i know this will only go as low as ISO200

Just one more thing ISO200 is the default for getting the best DR out of any camera, ISO100 you are actually limiting it DR slightly ie slightly more prone to blowing hightlights.

...DR?

that would be dynamic range I suppose

never thought that setting to ISO 100 could actually lower DR. I read that some pro cams has ISO200 at minimum, so it might be true.

yeah it's a known fact that lower ISO doesn't necessarily have better IQ,
some cameras offer ISO-50, not to gain any IQ, but to slow shutter speed.

Check your C. Fn II 3, Highlight Tone Priority. You should set it to 0 to disable it.

If that's not it, it could also be your Safety Shift if it only happens in Av/Tv mode.

Usually Nikon's are the ones with minimum default ISO of 200. They can be expanded though, sometimes down to 50.

It all has to do with the "native ISO" of the sensor. Each sensor behaves slightly differently depending on how sensitive it is.