Q. I'm planning to photograph and print old photos. I have my own darkroom and I also have two photo flood lights to use with a 35mm camera. What film processing and paper should I use? A. Try a fine-grain film such as Panatomic-X so that you'll get sharp enlargements. In copying you should somewhat overexpose and underdevelop. The overexposure will give you added detail in the dark areas of your copy and the under-development will hold down the contrast so you can print detail in the highlight sections.

The best way to arrive at the ideal exposure is to make a series of test exposures both over and under the correct indicated setting. For example, if your meter indicates a setting of f/8, make two additional exposures at f/8.6 and two more at f/11 and f/16. This will give you a series of five bracketed exposures. Since you're using 35mm you'll want to develop the entire roll, so choose four photos that you want to copy and repeat this test on each one.

Use a fine grain film developer such as Microdol or Ethol 90 and develop one-third less than the recommend developing time. If the recommend time is nine minutes, develop only to six. Examine your developed roll and determine which of the exposures is best.

The paper you use is simply a matter of personal preference since paper comes in a wide variety of grades and textures. Polycontrast is notable for its greater variety of possibilities from the same box of paper.

You may want to experiment with filters when making copies. A contrasting filter, such as a blue, will add detail to a faded sepia or yellowed print. An orange filter will eliminate orange stains. Q. Can you recommend a reasonably priced guide that lists all the cameras currently available? A. The newest in the $2.95 1980 Photography Directory and Buying Guide compiled by the editors of Popular Photography. Besides product listings there's a helpful feature called Buypoints which explains what features to look for.

Another is the $2.50 1979 Photo Buying Guide published by Consumer Guide Magazine. (A 1980 Guide is now being prepared.) This publication, about the same size as the Pop Photo guide, includes shopping tips and evaluations for particular products. Both guides are available in photo stores.

Amphoto (American Photographic Book Publishing Co.) puts out a useful book called Amphoto Guide to Cameras, by Hubert C. Birnbaum, which describes the advantages or disadvantages of each type of camera available. Q. What's the best telephoto lens to get? A. It depends on the kinds of pictures you want to take. For portraits, stage shooting, general candids, a medium tele of 80mm to 135mm is best. If you're into sports photography, motocross or auto-racing as well as birds and wildlife, you'll need a longer 200mm to 400mm tele.

For more specialized long-distance photography where you want to capture unusual effects, check out the mirror reflex cata-dioptic lenses in the 500mm to 1,000mm range. With these you can get enormous sunsets, huge moons, distant action and globes of reflected light on backlighted water.

The tele price will be in proportion to the focal length. Q. I have an Argus projector and was unable to buy slide trays locally until someone gave me the following address, and I've ordered trays from these people ever since: Argus Service Co., 511 Parson Street, West Columbia, S.C. 29169. A. Thanks for the help on the old Argus. Q. Is there a market for an 800 Polaroid Land camera? It's almost 20 years old and comes with a wink light and a photoelectric shutter -- all enclosed in a lined cowhide case. A. I'm not familiar with your model but the current price of the original model 95 is listed at about $30. I have two fairly old but absolutely rugged Polaroids I use for testing strobe lighting setups. These are the 110A models with a Rodenstock-Ysarex 127mm, f/4.7 lens that has shutter speeds from b to 1/300th of a second.

This model is the one that accomodates the Polaroid Type 42 roll film which has an excellent balck-white tonal range. Also it's one of the few that have both f/8-tops and shutter speeds so that I can convert the black and white exposure to the color equivalent.

I picked up one of my model 110As in a local pawn shop for $20. Q. I have a 35mm wide-angle and I'm thinking about purchasing a 24mm or a 28mm. Which would you recommend? A. Each lens' focal length has a particular use for the discriminating photographer, and one won't replace another. But, for the sake of variety, as you buy additional lenses you should choose the ones that are most different from the lenses you already have.

There's not that much difference between a 28mm and a 24mm, and as long as you have a 35mm, your next purchase should be a 24mm. When choosing your wide-angle lens, if cost is no object, choose a faster model, such as the Nikon 24mm f/2, over the same focal length f/2.8. It's hard to focus through a wide-angle lens with a SLR camera: the bigger the f/stop the easier you see through it. Q. I recently shot 12 rolls of film with far too many frames being overexposed or underexposed. I didn't expect such poor results and wonder if it could be my camera or lens. Where can I take them to be tested for possible malfunction? A. To find a reliable camera repair person, call local photographers that you may know, the ASMP (American Society of Magazine Photographers) office, the PPS (Professional Photographic Society) or other photographic groups for their recommendation.

Your local dealer is a possibility, too. But once you've found a good repair shop, stick with it and have your cameras checked periodically. It's a lot cheaper than losing 12 rolls of non-repeatable pictures. Q. How do I determine the proper flash exposure for a subject seated in a room with daylight shining through the window on the model? I'm using a 35mm camera that synchronizes at 1/60th of a second with flash. A. To get a good balance between the sunlit areas and the light from your flash, adjust the distance of your flash so its intensity won't erase the sunlit section. First, take a meter reading of the bright area with your shutter set at 1/60th of a second, and let's say with the film you're using it's 1/60th at f/8. In this case you would divide your flash's guide number (given in the instruction manual) by 8. If, for example, the guide number is 40, you divide 40 by 8, which equals five, or five feet. This is the distance you should shoot from for a good flash exposure.