Focusing screens with split image focusing aids are very sensitive to being exactly on the lens optical axis for clean imaging with the focusing aid. The Pentax K10D's screen retaining hardware and overall tolerances for positioning of the prism to focusing screen has a good deal of potential for inexact alignment. Modest speed, short focal length lenses can aggravate these problems, causing one or the other side of the aid to become darkened. Wearing glasses requires a higher eyepoint as well, relative to the viewfinder optics, which can also have an influence. I've never found the AF LED indicators to be terribly well aligned with the sensing area either but I wouldn't take that as much of a negative.
It's issues like these, btw, which are why I have always preferred a simple, plain matte fresnel focusing screen rather than one with focusing aids. The AF sensor system is in the mirror box so this problem to your eye shouldn't affect its operation. However, depending upon how the metering sensors which read from the screen are set up, you might find some variability in the metering. Godfrey On Jun 14, 2008, at 9:21 PM, Boris Liberman wrote: > I seem to have a problem/issue/strange thing with the K-E screen > that I > bought. It says (as I asked for it) that it has the optibrite > treatment > and all such. Now, if I mount that DA 21/3.2 I see that the bottom > half > circle in the center of the screen is slightly dark. If I mount FAJ > 18-35/4.0-5.6 that bottom half becomes seriously dark. I can still use > it somewhat for manual focusing but I am more concerned that like this > it really intervenes with AF and AE. > > I am shooting wearing glasses all the time. What have I done wrong? > > When installing the screen I did not hear the clicking sound when I > was > locking the filter in place, but I felt that I was closing something > very tightly. > > Also I noticed that the red light for the center AF point is just a > bit > lower that the center of the split screen circle... > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
