Re: Focusing SLR vs M

[Paul Schliesser <paulsc@eos.net>]

>May be I am missing something, but you can always tell which direction
>to turn using the semicircle focusing aid of an SLR. Just aim the
>isolated subject in the two semicircles in the center of the ground
>glass, the horizontal offset between the top and bottom half of the
>split image tells you which way to turn the lens, very much like the
>double image in the rangefinder. I personally almost never use the
>ground glass for focusing because it's too slow and sometimes too hard.
>Most manual focus SLRs, including R-series, have the split image
>focusing screen. It may not work very well when you use a lens with an
>aperture smaller than f/4 though.

This is true if you have a split-image focusing aid in your viewfinder, 
but not all focusing screens have them.

I use focusing screens with microprisms only, for instance, and a lot of 
people use plain ground glass screens or screens with only a grid.

- - Paul