Would you explain the practical difference between the rangefinder cameras and the more expensive SLRs ? A. The basic difference is that the rangefinder cameras focus the image through an optional system that fuses two separate images. By focusing the lens you align the two images. This system is both good and bad. It's good for focusing in dim light and for absolute focusing, which doesn't depane on how sharp your eyesight is but how careful you are in matching the two images. (Some pro photographers, such as Ernst Haas who uses Leicas, prefer this system.)

The disadvantage to the rangefinder system is that you don't see the exact image that the lens sees, so you have parallax problems when you focus up close.

The SLR (single-lens reflex) cameras are focused through the lens. Their advantage is that you see exactly what you take. The disadvantage is that they're hard to focus with a wide-angle lens.

Some pros use both a rangefinder camera for quick, accurate focusing and an SLR for long lenses and for composing exactly as the lens sees. Q. I have been using a 2x teleconverter with my tele lens. The results are very poor. What do you think is wrong ? A. You should make some test exposures to isolate your problem. The poor results could be the fault of the tele lens, the 2x converter or your shooting technique.

Use a tripod and carefully focus, then make a series of exposures. Next, shoot the identical scene with the 2 x converter on the lenses. Compare the results on a light table through a good magnifying glass Q. In a recent column you mentioned that some labs cut off part of the picture area because their automatic printers are set that way. I too have had this problem and am now thinking of doing my own color developing and printing . A. Before you go to all that trouble and expense try the custom printing that most labs offer. You will have to remember that the negative proportion may not be exact for the standard papers, so you may have a left-over margin. (For example, a 35mm shape will print up as a 7"x10" print on an 8"x10" sheet of paper.)