Children can be given a camera, claims author/photographer Tana Hoban, "as soon as they can choose something, hold the camera steady and press the button . . . know that they're pressing it when they're looking at a certain thing."

Her own daughter (now in her thirties) took pictures when she was still in a stroller--"a lot of low-angle shots."

"Adults miss the opportunity to ask children about what they're seeing," says reading and children's literature professor Karla Hawkins Wendelin, "because we don't think of it."

Instead of capitalizing on this "teachable moment," when the child sees something, is interested and asks about it, adults typically are in a rush to go onto other things, says Wendelin, University of Texas, San Antonio. She frequently uses Hoban's books as a "versatile resource" for her student teachers. "She doesn't miss some of these moments. She captures them in her photographs."

To encourage children's visual sense, Wendelin suggests "looking at things with children, and asking 'What do you see there?' Take time to notice the small details."

An exhibit of 50 award-winning, instant photographs by children, age 6-14, is on display through Feb. 25 at the Capital Children's Museum, 800 3rd St. NE. (Weekdays, school groups only; weekends, open to the public, Sat. 10 a.m.-4 p.m., Sun. 1-5 p.m.; 543-8600.) The "Young Expressions" exhibit, sponsored by the Polaroid Corp., includes a display showing how instant pictures are made.

Photographs by youngsters, kindergarten through 12th grade, may be submitted to the Young Expressions '83 contest. Deadline is July 30. For guidelines, write: Diane Bair, Young Expressions '83, 575 Technology Square, 9th Floor, Cambridge, Mass. 02139. Phone: (617) 577-2719.