1) Point of focus. The Canon and Sonnar do not stop at their infinity marks (actually, the Canon doesn't even have an infinity mark or focus scale), so I had to focus these two lenses as best as I could. The other lenses were set to their infinity marks.

2) Flare? This is what prevents me from posting my bokeh test shots. For some reason, the Pentacon mount lenses tend to flare out at smaller apertures when put on my Canon D-SLR. It is noticeable as a general over-exposure and washed out look in the F22 shots. The problem was really bad in all of the bokeh shots (where the lenses were focued at 2 meters), even at wider apertures. I'll have to look into this before posting more results.

3) Lens shade. This time I didn't use a lens shade on the Pentacon mount lenses out of laziness (but the Canon lens had its dedicated hood attached). I simply set the tripod in a shady area and took my photos. So no stray light was directly striking the front glass, but perhaps the use of a shade would have improved the color and contrast somewhat?

4) Representative sample. I am using my own equipment for these tests, some purchased new but other pieces purchased used. I do not know the history of the lenses I purchased used, and so some of them may have been disassembled or serviced prior to their coming into my possession. At any rate, the lenses tested here are assumed to be a "representative sample" of what is commonly available. Variations in manufacture among other things may skew the results, and so these test images may or may not accurately reflect what you can expect from a different lens specimen.