I KNOW IT'S A CLICHE, but you know how you hear the name of a new threatened indigenous nomadic tribal people, and all of a sudden you hear the same name five more times that week? Happened to me just recently.

The final time was on the deck of a very nice home on Telegraph Hill, at a party with small vegetables and barbequed oysters and overlapping conversations. Admittedly, it's a kind of borderline thing, to munch baby carrots while talking about threatened indigenous nomadic tribal peoples, but it is certainly better than munching baby carrots and pretending that the rest of the world does not exist at all.

I think I'm getting too old for irony.

The party was a celebration of the opening of the only noncommercial camera obscura in the United States. A camera obscura is (to simplify) a dark room with a periscope poked through the roof. The slowly revolving periscope gathers the images of the surrounding area and projects them on a round flat surface (like a kitchen table, except smoother and cleaner) in the dark room.

Think of it as a being in a submarine, except the eyepiece of the periscope is removed and another lens is substituted, a lens that enlarges the image and projects it downward.

The result, for the viewer, is the rediscovery of the intricacy and beauty of a familiar landscape. The light seems sharper and fresher; the shapes (reduced to two dimensions) surprising. And because the image looks so much like a painting, the movement with the image -- cars going down Lombard, an unsuspecting neighbor yawning -- is magical.

It was while waiting to go inside the camera obscura that we began talking about the Penan.

FIVE DAYS BEFORE, not four blocks away, I had looked at a work-in-progress about the Penan. The work is a collaboration between photographer John Werner, head of the Endangered People Project, the world's tiniest environmental action group, and Janey Fritsche, an artist and designer at the far edge of computer technology.

Using laser disks, hypercards and other info bundles, Fritsche is making an interactive computer presentation using images and sounds collected by Werner and others.

The images are striking; the music is hypnotic; the intent is political. The Penan live in Sarawak, that part of the island of Borneo that is controlled by Malaysia. The Penan live in (perhaps "are part of" is more accurate) the rain forest of the highlands.

And because the rainforest is being destroyed, the Penan are being destroyed. Some experts have already given up -- the Pacific rain forests are doomed; best to concentrate of the Amazon. Fritsche hopes that the intensely personal, visionary nature of the medium she works in will help persuade the way older forms cannot.

But there's a catch: The hardware is not widely available. Even if the project were finished tomorrow, there are few places where it could be seen. The race to revolutionize technology mirrors the race to cut down trees.

YOU DO WHAT you can; you use the gifts you were given. There are no easy answers; it may be that there are no answers at all. The Penan know things we can never know; killing their culture to make coffee tables is cosmically dumb.

But sometimes it seems that all we can do is sit in our darkroom with the periscope up, scanning the horizon for ships that never come, rejoicing only in the light that is still left.