Q - I've seen photograhers taking daylight pictures with flashes how do they know when the flash is just right?

A - There are two ways to use flash in sunlight: as if there were no other light, or adding just enough to lighten shadow areas while retaining the natural-sunlight look.

The first is easy, because your flash exposure depends entirely on your distance from the subject. Divide the guide number of your flash for the f-stop setting by that distance - if you're 10 feet away and the guide number is 45, the setting would be f4.5.

The second technique is more difficult. For this, use the f-stop setting for the sunlitscene and divide your guide number by the next larger f-stop opening to determine the distance for your flash. For example: If the outdoor exposure is 1/60th at f11, divide the guide number of 45 by the next larger opening (8) for the flash distance of approximately six feet. You'll get detail in your shadows from the flash and modeling from the sunlight. The problem is that the right distance for the flash may not be the right distance for the camera, to get the image size you want. Use an extension cord and set your flash on a light stand.

Actually, both of these methods of using flash are out of style. Today the natural look of flash-less outdoor photograph is in.

Q -I am 71 years of age and have been taking pictures for over 50 years, passing them on in albums with plastic sheets to protect the pages. Recently I learned that the plastic holds in moisture, causing the printes to deteriorate. I also heard that the color prints won't keep as long as black-and-whites and that I should copy them in black-and-white. I still have about 4,000 photos that I want to put in albums. What should I do to insure that these will be enjoyed by future generations? Stop using plastic? Copy the color in black-and-white?

A - Actually, the plastic sheets are a good idea, because they keep fingerprints off and protect the photos; the problem is to keep the moisture out. Ideal storing conditions are at a temperature of 70 degrees with 30 to 50 percent relative humidity. Try to stay within this by not keeping the pictures in a damp basement or a super-heated attic. Also, keep the albums in a tight-box with bags of silica gel (available in any photo store) to absorb the moisture.

Another source of damage to all photographic prints, especially color, is too much light. Don't leave the prints exposed too long to bright direct sunlight or you'll practically see them disappear before your eyes.

As for the color prints, the best thing to do is to edit them down to reasonable number and have these copied in black-and-white - unless you have the negatives. In this case, just keep the color negatives in a light-, heat-and humidity-controlled place.