Joseph McKenzie is protective of his prints, and with good reason. For, by making them public in his new show “Witness to Mortality” at Glasgow’s Gallery of Modern Art, he is exposing more than silver to scrutiny.

In the catalogue he declares that he has “made a pact with fact” and describes himself as devoid of the “remedial capability of the political wheeler-dealer”. In the eyes of this viewer, at least, he is under-selling himself. McKenzie transcends facts to lodge an indelible imprint on the collective memory.

His current work fulfils the promise of his earlier exhibition, “Gorbals Children”, mainly because he has continued to be the concerned photographer. The act of wielding a camera is not, for him, a snap-happy distraction from an academic life, but an activity which must be committed.

Some of McKenzie’s images are informed by the distress he feels on seeing the lives of his subjects, but his visual sophistication goes far beyond a subjective melancholy. He is a droll exponent of reportage in the pictures of Belfast in 1969, which are optimistic and occasionally funny: a British soldier, rifle in hand, patrols under a sign saying “Business as usual”; another trooper is a benign presence on a street full of children. These are the days before helmets, body armour or Bloody Sunday. A photograph of children reading comics on the barricades comes across as an act of defiance.

McKenzie may not be a wheeler-dealer but he is certainly political. Many of the photographs allude to the lost sense of community he found in the Gorbals and in Ireland, and he holds the planners responsible for its demise. Here, he is at his most ironic, as in a series called “Down among the dead men”. In the derelict Princes Dock a man is shovelling debris. To his left stand the unemployed cranes looking like anti-aircraft guns after a raid. The ack-ack is now silent, but McKenzie is still firing on all cylinders. The same series shows a statue of the Madonna presiding over a now non-existent row of tenements. The sadness, it seems, is that we destroy ourselves needlessly.

The most recent photographs suggest a man both quizzical and certain. “The Figleaf” brings a flagstone, or perhaps a gravestone, to life. A boy, the photographer’s grandson, is posed with spindly legs against a tree whose vast rings are visible and which looks as if it might live for ever. But it is the idea, the expectation on the boy’s face, perhaps even the human spirit that is timeless and recorded here for “future generations”.

The death of photo-journalism has been predicted throughout Joseph McKenzie’s career. Fortunately for us, he has ignored the false prophets and carried on taking outstanding pictures.