The new Nikon D7000 is out, and a lot of previews has touted the "native iso" of D7000 to be 100.
What does this actually mean? I'm assuming it means it performs at its best at iso 100, which means if you're ok to sacrifice light sensitivity, you'll get really great images...?
Answer
As I understand it the "native" or "base" ISO is the sensitivity you get without amplifying the analogue signal you get from the sensor. It becomes important when the native ISO is higher than the lowest available on a camera (e.g. the base ISO is 140 and the lowest setting is 100). In this case the camera is likely to overexpose the image (as you can't unamplify the signal to recover the highlights) and the non-amplified signal is more likely to be affected by the read noise of the electronics (then read noise of the electronics is roughly constant so if you have a small signal the read noise is higher by comparison).
As already stated it's unlikely to actually be noticeable in images however if you always strive to use the lowest ISO the camera offers whenever possible, you may be wasting your efforts as the image quality may be just as high/slightly better one setting up.
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