Q. I really am upset with the place that processed my film. I've just started taking pictures again after many years and was disappointed that many of my pictures were cut off. In some cases the heads or some other important part of the picture are missing.

I checked carefully and nothing is cut off on the negative, and when I questioned the store, they said that's the way it's supposed to be. What's going on?

A. The full 35mm negative is 24mm x 36mm, which has a width to height ratio of 2 to 3. Any prints made on paper with a different width to height ratio have to be cropped in one direction or the other. Many area labs routinely provide 3-by-5-inch prints. To print the entire negative, a print 5 inches wide would have to be over 3 1/4 inches high. Therefore, the 3-by-5-inch prints have to be cropped.

On the other hand, if you have the opportunity to get 4-by-6-inch prints, go for it. These prints have a 2-to-3 ratio and have become generally available. I pay an extra dollar per roll for 4-by-6 prints and find it well worth the money. With this size you're sure to get everything in the negative.

Similar problems exist with other size enlargements. To get everything in a 5-by-7 print, you'd really have to have a 5-by-7 1/2 print, so something must be cropped.

If you're really locked into 3-by-5 prints, compensate in your viewfinder. Take a step back before you shoot and include a little more room around your subject.

Q. I received a Pentax IQZoom for Christmas. I took pictures inside two different houses without extending the zoom lens.

All the pictures were beautiful except the people had red eyes in many of them. I called the camera store, and they said that's what happens with an autofocus and flash camera. My mother's Kodak brand camera doesn't get so many red-eye pictures. Should I take the camera back? Help!

A. I talked to Phil Kerswill, consumer product expert at Pentax, and we reviewed the entire red-eye problem.

Red eye is caused by light reflecting off the retina in your subject's eye.

The best way to avoid it is to move the flash as far as possible from the camera's lens. Since that can't be done on the compacts, there are several things to do:

Turn on all the room lights you can. This will make the iris in the eye smaller and lessen the amount of flash getting to the retina.

Have your subject look slightly away from the camera, especially in very dark situations.

If you're taking straight-on shots, have your subjects move their eyes and look away from the lens -- sometimes looking over the head of the photographer works.

The problem is that there is not yet a perfect machine. The super convenience of your camera is a trade-off. You can't move the flash, so red eye occasionally pops in.

Q. The various photography magazines carry articles with conflicting views on the comparative values of incident versus reflective light metering. Some proponents of incident believe that it is the only satisfactory method for any situation. My impression is, however, that many times reflective metering is better. Can you provide any guidance on this subject?

A. For a long time this debate was second only to the debate on whether slides are better than prints. Now, it appears that reflective metering is the leading method.

Incident metering measures the light source. It involves pointing the meter back toward the lens. Reflective metering reads light coming off the subject.

I join the side of reflective shooting.

First, meters built into modern cameras are reflective. They work beautifully in reading highlights, so very important in shooting color. They work so well, in fact, that my external meter rarely comes out of the bag.

If I'm doing outdoor portraiture, I sometimes use the incident meter. It's kind of like using a reflective meter on a gray card to get an average. This is especially good when the light is fairly flat.

The most important thing to remember is that a meter, any meter, is a tool. It's a guide to proper exposure. Neither reflective nor incident is the perfect answer. If you shoot the same situation over and over, you learn how to do it. But if your photography varies and you have new exposures to deal with all the time, it's a good idea to bracket (exposing a step or two each direction from the meter reading). I think it's easier to take a reflective reading in a new situation. But make no mistake, experience is the best way to learn how to expose for the effect you're looking for.

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