Originally posted by Aegon I think that ground glass screens don't work well with smaller aperture lenses.
I don't have firsthand experience in this regard, but you might want to look into it. It may not even be a problem to you.
I would disagree with this. In fact, years ago, when I was shooting film, my second body was deliberately purchased with a ground glass focusing screen (it was a Pentax KX) because when I used my 400/5.6 or my celestron C90 (1000mm F11) the split image in my Ricoh X-R-2s would black out, same for the micro prism collar around the split image, so I lost full use of the center of the viewfinder. A ground glass screen is the only way to focus small aperture lenses.
As for metering, you should do a test with your camera, and its present focusing screen, with your lenses and check the linearity of exposure vs aperture. I use a uniformly lit block wall and let the camera meter at each aperture, then check linearity by measuring the median greyscale value in the histogram. It should be about 115-120 for correct exposure, and if it moves by +or-45 then you have had a one stop change in metering. Two stops is 90 greyscale but after that the exposure becomes non linear. All shots should be taken using JPEG and neutral settings, I.e. no contrast boost, bright mode or other settings used.
You may find for manual aperture lenses this changes quite a bit as a function of aperture, and changing the focusing screen can , due to differences in light transmission and scatter off the focusing screen , lead to very interesting results
See this thread, and the chart I attached and you will understand what an impact a focusing screen can have on metering performance
Do not hesitate to reply or PM if you want to discuss further
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/124627-k-5-met...-lenses-2.html
Last edited by Lowell Goudge; 01-09-2013 at 11:29 PM.