Generally, what type of lens does a professional photographer use on model such as Cheryl Tiegs? A friend who works with Tiegs said he uses an 85-mm to 90-mm lens. The lenses that I use for portraits are a 55-mm f/1.2 and a 135-mm f/2.5. Are these lenses used in commercial-type photography? What focal length lens do you think is best for portraits? A. My favorite lens is also an 85-mm for models and portraits. I prefer this lens because the perspective is pleasing and I can work at a good shooting distance. Another plus for this lens is that at the larger opening the depth of sharpiness is right, i.e., the main features are sharp but there is a soft-focus effect in front and back of the plane of focus. Q. I have a Nikon F and use the 55-mm and 105-mm micro lenses for closeups. Many times when using an ASA25 film I'm not able to get the depth of field I want to slight breezes that require shooting at a minimum of 1/25th a second. Is there any way of getting depth of field and speed by using fill flash, since my camera won't synch at higher speeds? A. Using a fill flash will solve your problem. The subject movement will be stopped by the speed of the flash duration, which in most models is less than 1/1,00 of a second. And if you place the flash close to your subject you will be able to stop down to a smaller opening for added sharpness. Actually, by using a flash you will be taking the photo not with the shutter speed of the lens but with the instaneous light of the strobe flash unit. Q. How can I sell my pictures? A. This is a frequently asked question. One of the answers is to look at the publications and determine which ones use the kinds of pictures you take. Then send in samples of your work with a stamped self-addressed envelope for their return.

Another possibility is to sell through picture agencies. One, which I have mentioned before, is Compupixrental, managed by Associated Photographers International of 21822 Sherman Way, Suite 101, Canoga Park, California 91303.

Another is Photoletter, published by Rohn Engh, which can be requested through the Photoletters, Osceola, Wisconsin 54020.

Both these agencies are reliable and may be able to help market your photos.

Q. How can I show the lines of rain on a rainy day? I can get the rainy-day effect right but the raindrops or streaks don't show up. A. The way to show rain falling is to shoot toward the light so that the raindrops or steaks of rain will be back-lighted.

To accentuate the highlight effect, choose an angle that puts the back-lighted rainfall against a dark area -- such as a building, roadway or foliage.

If you want sharp lines of rain, use your highest shutter speed and adjust the lens opening for the exposure.

You can add to the rainy effect by including drops of water from foliage or the eaves of a house. When you do this, be sure to focus exactly on the water droplets so they stand out in sharp relief.