Thanks for the input everyone!
I conclude for me, almost exclusively
manual focussing with the original matte screen on K100D:
- slight daylight backfocus could be the rule (that's so with my cam)
- basic 'lens laws' would dictate this problem to be especially delicate with high speed apertures and/or longer focal lengths (that's so with my cam)
- stated in the linked articles, and most important for me: It depends on the lens (even between same FL/speed lenses). I don't like this fact, cause I happily change between say 30 lenses or more, so I should really concentrate on some of them and really know their behaviour - Know thy lens!
- last, I've read somewhere that you can already estimate a lenses' color-sensitivity (performance-wise as well as focus-wise) if you look at the distance from the red infrared-mark to the 'daylight' mark (only same FL/speed is comparable)
If Pentax and Nikon should be in the same camp on this one, and Canon would be on the other side, somebody doing some basic comparative testing would be nice :-)
(if picture shows: f1.2/55 at near distance. Tough focus anyway)
Thanks again for the valuable info,
Georg (the other)