"You can't appreciate space in a movie," says Philip Johnson in the movie about his life as an architect that airs tonight at 9 (on Channel 26 and Maryland Public Television stations), thereby encapsulating the difficulty of translating the beauties of one medium into another whose essential qualities are different.

The camera does, as Johnson says, flatten out the spatial experience even when moving around, which it does a good bit in "Philip Johnson: A Self-Portrait," the second installment of the summer-long "American Masters" series.

Not that this is a matter of great consequence. The program is mainly talk (interviewer Rosamond Bernier staying maybe a bit too respectfully in the background), and Johnson is entertaining and informative when talking about his favorite subjects -- architecture and Philip Johnson.

Probably the best visual sequences are privileged glimpses we get of his home, grounds and private museums in Connecticut. We see Johnson and Bernier close up and at a distance sitting in his famous glass house on a hill as the architect explains, interestingly, that a paramount aim of all that transparency was to pin nature to the wall, so that the landscape becomes "a sort of wallpaper."

We see Johnson, who turns 80 next month, fearlessly leading a precarious climb up the cinder block tower he built in the woods (it is called for some reason the Lincoln Kirstein tower after his friend, the great balletomane). We see his superb collection of 1960s art in the equally wonderful spaces he designed for it. Hands in action, Johnson says terrifically descriptive things, such as "It all settles down here like a dog," to explain just how the spaces work.

These vignettes give us a feeling for Johnson's personality -- at once warm and sharp -- and for how fascinated and in love with architecture he has been through his life. There's also an up-close sequence of Johnson and his partner John Burgee, perhaps the premier architectural salesmen of our time, putting on their impressive show for a prospective client. Johnson's technique, he says, is "to look 'em in the eyes."

With an exception or two, neither the camera nor the architect himself does so well when presenting the products of his long career; the film is like a string of moving snapshots of buildings, and Johnson's commentary, though rarely irrelevant, is very snapshotlike. This is not without value, in that Johnson's late flowering has produced a remarkable list of good-to-great buildings, but it is definitely not probing material.

And sometimes the commentary gets gushy. Johnson, says Bernier, "was born to make waves, and has made them on a scale that would be the envy of Neptune himself." Such comments are not likely to faze the architect, though -- at one point, without blinking an eye, he compares himself, not unfavorably, to Shakespeare.