The surveillance tape that captured D.C. Mayor Marion Barry smoking crack cocaine at the Vista Hotel is fuzzy and blurred by studio standards but is a "very good video" under the severely limiting circumstances of covert camera work, a forensic specialist said.

"I've seen some where you couldn't tell what was going on," said Anthony J. Pellicano, a tape analyst in Los Angeles. By comparison, he said, the Barry tape "was actually pretty good."

Pellicano, who has examined the video and audio portions of the Barry tape, said the surveillance appears to have been done with two cameras and two to four microphones in the bedroom of Room 727 at the Vista Hotel. A third camera was mounted in the bathroom.

The FBI, which spearheaded the surveillance, would not describe how the cameras and microphones were set up.

Pellicano said several factors work against studio-quality film in undercover operations.

Law enforcement officers usually must prepare the surveillance site on short notice and must do their work clandestinely, he said. Also, they must avoid using bright lights to prevent suspicion. The lenses of surveillance cameras are tiny, limiting the amount of light entering the camera and reducing clarity.

In the Barry surveillance, Pellicano said, one camera appeared to be hidden inside a television and the other placed in an adjacent wall or possibly in a briefcase or piece of furniture in the bedroom.

Pellicano, who analyzes tapes by a complex computer enhancement process at his labs in Los Angeles, said the specially designed video cameras can be "as small as the palm of your hand." The microphones, he said, were "apparently not attached to the cameras" but separately mounted and separately wired.

The hotel room television was turned on during the 83-minute surveillance of Barry and Hazel Diane "Rasheeda" Moore. To minimize interference, Pellicano said, FBI technicians apparently used a device called a digital predictive filter to screen out the TV noise.