Q: I'm trying to take a photograph that turns out to be just black on white, with no middle gray tones. It's like a line photo. High-contrast film processed on grade six paper isn't right. I just have a Minolta SLR. How can I get this effect? A: What you're talking about is a two-tone posterized print. While posterization can be complicated, you may get satisfactory results with simple equipment by making your initial exposure on Kodak High Contrast Copy Film 5069 (available in 35-mm size -- 36 exposures). After taking a meter reading, deliberately overexpose the shot by one to two f/stops. Then overdevelop the exposed film by about 20 percent in Kodak D-19 developer. (If normal development calls for five minutes, develop for six.) From there, print onto a high-contrast paper. If you still have middle-gray tones, try bleaching them out and rephotographing the print to produce a permanent high-contrast negative. For more on posterization, write Kodak, Rochester, N.Y. 14650, for pamphlet No. E-93. Q: Can you tell me your opinion of the Olympus OM 10 as compared to the Canon AE-1? I've seen OM packages that include a 50-mm f/1.8 lens, a 125-mm f/2.8 telephoto, electronic flash, and cable release for $279.95. I have a Ricoh 500 camera with auxiliary wide-angle and telephoto lenses for which I've been offered $45 and for a Zeiss Super Ikonta, up to $150. Would they be fair trades? I take mostly color prints of the family and school activities. What would you do? A: The price seems good for the package, but I wonder if the 50-mm and 135-mm lenses are best for you. Would you get more use from a 35-mm wide-angle and an 85-mm portrait lens? Or a 70-to-150 zoom?

As for a fair trade, no photo store will give you what your equipment is worth: they must mark it up in order to make a profit when they resell it. In good condition, your Ricoh, etc., could bring from $125 to $175 from an ad placed in the paper; and the Super Ikonta should be worth nearly $200. In your ad, ask as much as you think the equipment is worth "or best offer." You'll be dollars ahead.