Photographs of children can make memorable presents

''There are very few gifts that parents and grandparents enjoy more.''

As he leafs through a portfolio brimming with shining faces and shy grins, Robert Bachrach is talking about one of his favorite subjects - photographs of children.

''Kids are so naturally graceful,'' he continues. ''Especially kids of royalty. You find 3-year-olds with very courtly manners who, from birth, have been prepared for their calling. They're incredibly well behaved.''

The hallway leading to the Bachrach offices here is lined with portraits of the regal and renowned, from His Royal Highness Prince Faisal Ibu Abdul Aziz al Saud to the late Boston Pops conductor Arthur Fiedler. Every United States President since Andrew Johnson has sat for a Bachrach portrait, and while John F. Kennedy and Ronald Reagan gaze authoritatively ahead on one wall, the Franklin Delano Roosevelt family strikes a more casual pose. In among the movers and shakers, there also are captivating photographs of blond toddlers, who already appear to be making their marks in the world.

The oldest family-owned photography firm in the US, the Bachrach studios are run by Fabian Bachrach and his sons Robert and Louis, the third and fourth generations to take their places behind the view cameras. Although most of their work involves business and wedding photography, the three Bachrachs spend a lot of time taking portraits of families and children.

''Generally, it's easier to do kids in a family group,'' Fabian Bachrach explains. ''Children are secure within the family, but take their mothers away and who knows what will happen? If they're under three, it's even more unpredictable.''

Robert Bachrach nods in agreement, adding that he often has to draw the age limit at six months. ''Parents looking for memorable photographs aren't going to get very much before infants can sit up - unless they want a picture of the mother holding the baby.''

In the portraits he takes of children, Robert says he tries to get as close as possible to his subjects. ''Lots of times I try to stand about five feet away from a child. With little ones especially, you have to be in physical contact with them. If you can hold the camera release in one hand and do your tickling with the other hand, it works pretty well.

''Lots of times you kind of make a fool of yourself trying out different things - puppets, keys, patience. Sometimes it works, and many times just getting children to look at you with a pleasant expression is tricky!''

Most important to a good portrait, says Robert Bachrach, is the trust a photographer develops with a child. ''They sense right away if you're not comfortable with them, and then you can't get through to them at all,'' he explains. ''They have to sense that you really like them for you to be able to do a good job.''

Although prices vary widely by region, an hour sitting with a professional photographer for a family or child's portrait can range from $45 to $150. Most studios provide a selection of between 10 and 20 proofs to select from. Finished color photographs average $20 each for 8-by-10-inch prints; $50 each for 11-by- 14-inch prints. Processing can take between one and four weeks.

''It all depends on what you're looking for,'' Robert Bachrach adds. ''Parents who take their children to the department store photographer every six months and pay five dollars a sitting are getting a pretty good deal, too.''

Many parents, of course, would rather take their own candid pictures of their children. Fine, says photographer Jill Krementz, but be prepared to put up with objections from older children.

''Taking pictures of other peoples' kids is a lot easier than taking your own children,'' she explains. ''Your own are likely to think you're a fool, and to say, 'Oh, mom, stop bugging me.' ''

Ms. Krementz is author-photograher of the popular series of ''Very Young'' books which feature child dancers, riders, gymnasts, circus flyers, and skaters. Her latest book is ''How It Feels To Be Adopted'' (New York: Alfred A. Knopf. 107 pp. $11.95).

''Parents shouldn't be reluctant to 'direct' a photograph,'' she notes. ''Arranging kids makes them feel more secure, and parents should simply tell two kids to stand closer together or to put their heads together, if that's what they want. Children usually do what they're told.''

There are two common mistakes many parents make, she adds. ''If they stand too far away from their subject, they'll get too much junk in the picture, and using flash attachments or cubes makes kids blink too much.''