I just got a Nikon D200 and no matter what ISO I set with the thumb adjustment, when I look through the viewfinder my ISO is 8000. What am I doing wrong?
If that's not the problem, try posting a photo with full EXIF data so we can see what's happening. Sometimes it's easier to post it to Flickr and provide a link to it there.
High ISO NR Noise reduction reduces noise at all iso levels but more effectively at Higher ISO also with the lose of fine detail when shooting jpegs,but what does this have to do with the iso speed being taxed to 8000 ISO and 8ooo on a D200 is not possible when native iso is 100-1600 extended boost up to 3200. I think you where looking at your shutter speed even so turning on the high NR should never change your ISO speeds,hope this helps some but perhaps this will.
Nikon D200 user Guide.Nikon | Download center | D200