When shooting with my 135 macro on the Pentax 67, the aperature goes from f22 to f32 with no 1/2 stop detent. This can be a problem when max dof is required, since the shutter only has full stop adjustments. I am considering using 1/2 and 1/3 stop neutral density filters to tweak the exposure. Has anyone used this technique or others they'd care to share info on? <p> Thanx, Jim.