Q. My questions center on the purchase of a new camera. I am not an "advanced" amateur, but neither am I a complete novice.

I've had my Nikon F2 stolen. I assumed the "natural" replacement would be the F3. Now I'm not sure. I had thought I didn't need, or even want, any of the new, advanced electronic gimmicks. I was content to "do my own work." But now that I read and hear so much about the Canon EOS, the Nikon 4004 and the Pentax SF1, I'm thinking that I perhaps should join the electronic photo age.

The big question: If these "new" cameras can do all and are the end all, how come they cost less then the Nikon F3, the Canon A1, and the Pentax LX? I would think that you'd have to pay for all these electronic features. Does this mean the new, fancy cameras are lesser ones?

A. Not lesser, but different.

The F3, A1 and LX cost more because of the way they are constructed. It is usually less expensive to manufacture a camera regaled in computer chips, circuit boards and other electronics.

On the other hand, the construction of the top-of-the-line "mechanicals" is heavy-duty. Some have titanium shutters, the seals are especially effective, and the LX, for example, has ball bearings at 10 separate points of movement.

Both, however, require care. No camera today will take being dropped on cement; very few will stand up to constant exposure to salt air. But from a professional standpoint, it's safer to "run" with a mechanical camera than an electronic. I personally think they absorb shock better.

Most folks don't have to "run" and are smart enough to keep their equipment clean and properly protected. So your decision may boil down to what kind of photography you like and how much money you want to invest.

The electronic cameras are wonderful -- but designed to do things in a different way. It's like comparing Mercedes-Benz to Cadillac. Either is great to drive.

Q. Recently I sent a Kodacolor negative to a Kodak processing lab to have a 20 x 30-inch poster made. It was sent back to me with a form letter telling me that the film was an older type that has not been manufactured for many years.

The Kodak letter went on to say that I should use up-to-date film. Well, when that picture was made in the 1960s, the film was fresh and up-to-date.

I can appreciate Kodak not being able to process film that was more than 20 years old, but why can't they make prints from processed negatives? This negative is part of a collection of historic DC fire stations and equipment. Does this mean that other photographers with valuable pictures shot on early Kodacolor emulsions will find those pictures useless and unprintable?

A. I spoke to some Kodak people at Rochester and they are not very happy with this situation, either.

They suggest that you try it again, since they have a program now operating in which every attempt possible will be made to print these older negatives.

The problem is with state-of-the-art computer printing. With the advent of VRG emulsions, the chemistry of both film and processing changed. The orange mask is different as is the processing chemistry. Today's processing equipment is designed to handle the newer film. Re-setting it to handle the older emulsions is a difficult proposition.

Now Kodak tells me they are trying to change this. If the negative is in good shape, and of decent density, they will make every effort to print it.

Q. I am planning a vacation to the Caribbean this spring and have recently acquired a used Nikon Nikonos underwater camera. What film should I use for the best color in underwater available light?

A. First, you should test that camera before you depend on it. You can do this in your swimming pool or bath tub. Just don't wait to submerge it for the first time when you're on vacation.

For slide film, I'd go for ISO 200. For print film, ISO 400. Remember, too, that your effective shooting distance is from 3 1/2 to eight feet.

FEEDBACK: C. J. Aronson, of Kensington, wrote about taking pictures from a moving vehicle: "While you're doing this, be sure to keep the camera as close as possible to the window to avoid undesirable reflections. Just be sure that sudden stops or motion don't jam the camera {against the window} and cause damage."

A good thought, but be careful about touching the lens to the window. There might be vibrations to mess up the shot. I have used a piece of foam rubber beween the window and the edge of the lens and it does help steady things.

Robert Cummings, of Alexandria, suggested a solution to red eyes in flash pictures: "Over many years of this happening from time to time and knowing what caused it, I've found it easier to use a felt-tipped pen and spot out the red area. That area is supposed to be black anyway so this works every time."

Write to Carl Kramer c/o Weekend, The Washington Post, 1150 15th St. NW, DC 20071.