[Leica] Split field density

["Roy J. Feldman" <royfel@hotmail.com>]

Any one tried to use split density on M cameras. I realize that if I place
the line right down the middle I'll have no problems. But how about say 30%
down. I know that on a normal SLR (I use pentex 6x7) that I must reposition
the filter as the lens closes down(i.e. if I cover the top 30% of the image
with the lens wide open as the aperture get smaller that 30% might now be
only 10%.)The obvious answer is to use a slr but I believe the photography
should be as difficult as possible. I'm not looking for a physics lesson
here, just some anecdotal advice.