Originally posted by Gingerthecat Will a different focusing screen help?
I had a split-prism screen for my K10D and it worked well. It is an easy job to replace the existing screen. My one did not introduce any exposure errors into the mix when using matrix or CW metering, but spot metering was affected.. it was made by KatzEye in the USA, sadly no longer in business, but if you do go for one I suggest you look for this brand.
I suggest you do some proper experimentation with your camera on a tripod to establish exactly what the problem is:
Check diopter setting
Are you able to achieve infinity focus ? Possibly the lens is at fault.
It may be that the the registration distance of the viewfinder no longer matches that of the sensor. The mirror may be out of alignment or indeed the focus screen my not be seated properly, or even the prism may be damaged I would start by removing the focus screen and replacing it to check (don't touch or wipe the surface of it.) your testing should show if the camera is front or back focussing due to alignment problems.
One final thing I would say is that you are right to stick to "A" series lenses or later. Although you can use M or "K" series lenses with the K10D you will have exposure problems when using the stop-down metering method required for the earlier lenses, even when using the stock focus screen. There was quite a hullabaloo about this when it was released. Funnily enough my KatzEye screen gives better results when using stop-down metering that the stock screen.
---------- Post added 04-19-19 at 12:21 AM ----------
Originally posted by BigMackCam How do you find accuracy of the various metering modes with the replacement screen? I found I could get away with matrix metering (with some adjustments, depending on the scene), less so with centre-weighted, and all bets were off with spot metering. It was metering inaccuracies that eventually caused me to revert to the original screen...
I used a KatzEye screen and had no problems metering except for spot which was unusable.
See my comment above for how the KatzEye was actually an improvement over the stock screen when using stop-down metering with K and M series lenses.