IT IS unfortunate that when I entered the press preview of the current Hans Namuth retrospective at the National Portrait Gallery I had to walk past a glorious portrait of Duke Ellington made by Irving Penn. That portrait, and others of the jazz great, were on temporary display at the time.

In a whole room full of Namuth's portraits -- many of them quite good, a few really excellent -- there was hardly anything to rival the Penn picture for intimacy and excitement.

How does that happen? How does one photographer's work transcend another's, even when they both have spent a good part of their careers walking the same visual ground, covering many of the same subjects?

In the case of Namuth (1915- 1990), the unfortunate comparison might not be so much with Penn, but with such contemporaries as Arnold Newman. A look at Namuth's work, as well as that of some other photographers, might provide a few helpful answers about what exactly goes into making a first-rate environmental portrait.

But before that, this caveat: I am an environmental portraitist, too. I have my own style and, therefore, my own stylistic preferences and prejudices. What I like you may not like, and vice versa. So take my advice with a grain of salt.

To me, one of the most important elements of a good portrait -- besides, of course, the expression on a person's face -- is depth. Depth occurs when there appears to be more than one visual layer to the photograph -- when, for example, the eye can wander over and around a number of elements: down a corridor, perhaps, or through a window, or beyond a wall, and become aware of a visual context of the subject. In a tight close-up, this depth can be achieved by directional lighting, creating interesting planes of light and shadow across the subject's face.

One way to achieve this end is through longer-than-expected shutter speeds to bring up the ambient light around the subject and to better render the background. When combined with even a single flash unit or flood to light the subject, this technique can mimic the look of multiple lighting and create a dramatic image.

In "The Edge of Time" (University of Texas Press, 1998), a collection of photographs of Mexico, photographer Mariana Yampolsky repeatedly uses a similar, though perhaps simpler, technique to make wonderful images. She just seems to be aware of great light and has the genius to preserve it on film. One such photograph, "Asi' la construi' " ("This is how I built it"), shows a seated peasant in a white linen suit gesturing with his gnarled dark hands in what may be a rustic courtyard or bare interior. He is sitting in what seems to be a dirt-floored stone building -- a rough ladder is just out of frame to the left near a wall. Shadows fall beautifully on his suit and on the background and the entire image creates a serene harmony in black-and-white that is as lovely as it is multilayered.

By contrast, too often in Namuth's work -- especially in his portraits of artists in their studios -- the photographer seems content to make little more than record shots of the artists in front of their canvases or sculptures. The subjects might as well be sitting in front of gray seamless paper for all the depth Namuth creates in his pictures. To make matters worse, the lighting tends to be maddeningly uniform. Doubtless, in Namuth's color work -- much of it first published in ArtNews magazine -- this allowed for crisp and accurate rendition of the subject's artwork, but it also made for some lackluster, not to say boring, portraiture.

Consider two photographs of the painter Edward Hopper, one by Namuth, the other by Arnold Newman. Namuth's portrait of Hopper and his wife Josephine, made in 1964, shows Hopper at his easel, dabbing a brush into his palette, his wife in the background staring into the camera. That's it. The lighting is even, the composition pedestrian.

Newman's portrait, made four years earlier, also at Hopper's studio in Truro, Mass., is glorious. Rather than place the artist in front of a canvas, Newman places him outside on a bench, the large shingled studio forming a dramatic backdrop in the stark afternoon light and evoking the stark images Hopper painted. Hopper's wife is in the picture as well, but as an enigmatic figure in the background by the studio, silhouetted against the sky. Multiple layers. Dramatic lighting. A great portrait. A great photograph.

HANS NAMUTH: PORTRAITS -- Through Sept. 6 at the National Portrait Gallery, Eighth and F streets NW (Metro: Gallery Place/Chinatown). The gallery is open from 10 to 5 daily. Call 202/357-2700 (TDD: 202/357-1729).

Questions or comments? Write me c/o Weekend, The Washington Post, 1150 15th St. NW, Washington, DC 20071 or via e-mail at fvanriper@aol.com

Next week in this space: Stamps and Coins columnist Bill McAllister.

CAPTION: In Hans Namuth's portrait of artist Edward Hopper, the lighting is even and the composition is pedestrian.

CAPTION: Arnold Newman took Hopper out of the studio, utilized dramatic lighting and created a multilayered, dynamic photograph.