In article <4ghd8m$jj7@eng_ser1.erg.cuhk.hk>, mkleung@cs.cuhk.hk says...

>My body is F90 (no X).
>Is there any means to adjust the shutter speed in 1/3 stop at mode M?
>As I know, mode A and mode P would adjust the shutter speed stepless.
>However, don't know about at M mode.

Use the aperture ring - it is infinitely variable, with detents at only
the whole stop positions, thank goodness! ;-)
Hope This Helps