This is a brilliant exhibition. Brilliant for its consistently sharp and vivid images. The images themselves are 50 years old, and were taken as a very young man by Martin Karplus during his travels in North America and - as a post-doctoral fellow at the Mathematical Institute here - in 1950s Europe. And they reflect something of the brilliance of a voyage of discovery by a keen mind and eye among new experiences of culture, art and life.

On a later Oxford visit, this time as the prestigious George Eastman Professor in 1999, Martin met "a marvellous photographic craftsman Paul Sims" (his description) whose skill produced digital prints from the then aged slides. Printed on archive paper to last 75 years, a selection of 67 from the original 1,000 are on show at Wolfson College till November 30 (10am-4pm daily).

At first one might attribute the brilliance to the Mediterranean sky which dazzles in many studies from Italy and France; indeed there are few grey skies except, strikingly, in the Bguinage at Bruges. The figure of a nun appears also in a cloister at Beaune with its patterned Burgundian roof-tiles.

Several of the photographs can be grouped by place or theme, though they are so cunningly hung that this not always clear. Two taken at Collioure beach in Southern France, for instance, show a fisherman with his nets at noon, and the same shingly beach at night with just the black shadow of that spread netting. Some are lucky' shots' like Martin's own favourite with startling contrasts of colour and the detail of the little girls' uniform. For others he waited two days with plentiful offers of cigarettes; these are mainly his studies of Yugoslavia, often stark like the labourers tilling the red soil by hand, or more bucolic rural scenes. He's equally unsparing in his views of the US and Mexico, like the broken-down shack framing a woman and child (above), or the desperate ruined hilltop Navajo reservation in Arizona.

More tranquil rewards of patience are the reflections of water, all at different locations, all exactly observed, at Martigues, Besanon, Florence or Leyden. I noticed too the same cutting-edge contrast technique whether in the geology of the Canyon in Utah or the Colosseum blazing against the black columns of the Temple of Venus.

Martin tells me he now owns the latest digital camera. so there will be more to come.