Originally posted by deus ursus I haven't thought of that. I don't have an MX, but an LX with an SC-21 screen. I found it quite demanding to focus with the M 50/1.4, but thought it was nothing I could do about it. Maybe I should look for an SA-23?
Yea, not sure what your definition of demanding is, the MX I have was fully CLA'd in november, and it came with a 28/3.5 from the seller. I don't know if the repair person (receipt shows Eric Hendrickson as the person doing the work) checks against their own high speed lens, or if it's basically just a collimator (sp) to the focus screen.
I would have to do another test to be sure, but for example, close up at f/1.4, I could have sworn I focused on the toy robot, but it seems like the camera in front of it was focused. There were other shots at a distance indoors at f/2 (and some f/1.4) where the point of focus seemed 'soft', but it wasn't any sharper closer in front (and the wall would be behind it, so no way to know if the lens is just softer on film than adapted on my digital, or if the focusing screen isn't critical enough for 1.4) But course it was a handheld shot, the only way I can be sure for certain is to tripod it, especially since 1/60th with a 50mm approaches the bare minimum to handhold an SLR (I'm used to mirrorless and rangefinders which don't have a mirror slap).
But I also wonder if I changed my distance slightly when I metered, moved the camera way from my eye, changing settings, and then recomposing without refocusing.
From my past experience the split in the middle is usually sufficient enough for f/1.4, it's the microprism ring that could be a little harder to discern (more so as the lens gets slower, but I guess there might be a point where precision becomes harder to pinpoint when the lens gets faster?)
Though these two seemed spot on, though I can't remember if it was f/1.4 or f/2, I know for sure it wasn't over f/2, I think on the smokey artwork, I had it at f/1.4 because I bumped the shutter up to 1/125 to make it easier to handhold. On the first one I focused for the edge of the artwork (and not the plaque), so that might have been 1.4 as well. The second I focused on the slit down the middle.
PS: You can use the MX and LX screens interchangeably, from what I read using an LX screen in an MX does affect the meter reading slightly, but an MX screen in an LX doesn't affect it (apparently metering isn't reliant thru the screen on the LX).