What we have so far, then, is this: a picture whose technical shortcomings are shared by any number of amateur snaps, of second-class citizens/artists/gods, taken by a photographer of undisputed international stature.

Coltrane’s eyes are shut; he seems almost a baby in Webster’s rough, tender embrace. (As “Cool Cats” makes plain, Webster could go from teary affection when sober to threatening to pull a knife when drunk.) Coltrane had not yet become a legend, a legend who said he wanted to become a saint, the holy figure as immaculately conceived by Chuck Stewart for the cover photo of “Ascension.” He had not yet made the radical assault on the tradition of which Webster is the mature embodiment. Webster had been around long enough to see and hear earlier revolutions in the music and would live to hear several more. It may look as if he is giving Coltrane his blessing, but it’s impossible to tell whether we are witnessing a greeting or a leave-taking. This is entirely appropriate, because in jazz, the two are often the same (as when we recognize the opening bars of “Ev’ry Time We Say Goodbye”).

What we see is what we hear in many of Coltrane’s greatest recordings: a greeting that is also a leave-taking. More broadly, the jazz tradition is made up of assaults on what has gone before and elegies for what has passed: Lester Bowie’s joyous tribute to Louis Armstrong (on “All The Magic”) or George Lewis’s heartbreaking “Homage to Charles Parker.” In some cases, assault and elegy occur simultaneously, throw their arms around each other, so to speak, as happens when Cecil Taylor goes to town on Mercer Ellington’s “Things Ain’t What They Used to Be.” We look back elegiacally on this moment in 1960 when so much revolutionary jazz and so many elegies lay in the future.

In an interview with the photographer Lee Friedlander and his wife, Maria, the soprano saxophonist Steve Lacy said how lucky he was to have played in the 1950s, when so many of the greats were alive. Friedlander responded that “in 1950, 85 percent of the history of photography were living people.” We can quibble with this — obviously Friedlander is referring mainly to 20th-century photography — but between them, he and Lacy enable us to appreciate the extraordinary convergence taking place in a picture made 10 years later, in 1960. In a photograph with no setting, nothing external to itself, there is so much context, so much history. A picture of two musicians, it is also necessarily the record of a trio session with DeCarava as leader so that, in the context of photographic history, Coltrane and Webster are sidemen.

Jazz, it is often said, is about being in the moment. By excluding narrative, DeCarava affirms the importance of the moment while simultaneously expanding it. In one way the shutter speed is too slow to record clearly what is happening in this moment. But this technical failing succeeds in allowing more time to leak in to and spill over from the picture. So let’s articulate the way it’s framed through a different form of improvisation. Imagine that it was part of a patterned carpet of images. We can’t know exactly where it was located in that pattern, but we do know that whereas history is concerned with beginnings (in jazz with Buddy Bolden or Louis Armstrong), with the chronological order of events, the pattern on a carpet converges on a center. This picture looks as if everything around it has been eaten away by time. We are always working our way out from it — or back toward it. In that sense, it is the central photograph in jazz.