This has been bugging me for a long time and I'm not even sure how to word it, but here goes.
With some lenses both the top and bottom of the split image in the viewfinder are very clear. With other lenses the top section is fuzzy and looks very low contrast. My eyesight isn't all that hot so the split is important to me, especially in dimmer light. I tried 5 different lenses and here is what I got: 1.) SMC Pentax-A 70-210 F4 at aprox 105mm = Top and bottom very clear. 2.) Vivitar Series 1 70-210 F3.5 at aprox 105mm = Top and bottom clear. 3.) Vivitar 28-105 f3.5-4.5 Macro at 105 = Top VERY fuzzy, bottom clear. 4.) RMC Tokina 80-200 F3.5-4.5 at aprox 105mm = Top a little fuzzy, bottom clear. 5.) Tamron CF TELE MACRO 70-150 F3.5 at 105mm = Top quite fuzzy, bottom clear. 1 and 2 make sense, these are fine lenses all around. 3 makes no sense, this is also a very good lens. 4 makes no sense, this is a relatively poor, low contrast lens. 5 makes no sense, this is also quite a good lens. (Lenses rated good/bad on actual photo results) The camera is a Super Program, the viewfinder is squeaky clean. I tried with my glasses on, and with a diopter instead, no real difference. All lenses are, of course, close in maximum aperture. Number 3 bothers me the most, I love this lens and the resulting images are very sharp. It is quite prone to flare but other than that is very nice. I used a light source from over my shoulder. Indicated exposure at ASA 100 was 1/60 to 1/125 with lens wide open. (To give an idea of light level.) The targets I used were flat black and flat white 1/2 inch dowel rods stood vertically 4 feet from a light gray wall. I was at a distance of about 12 feet from the rods. Any ideas? Don (The puzzled COF)
