These two fascinating exhibitions by two very different photographers challenge John Steinbeck’s belief that cameras should be disparaged because ‘they are so much more sure than I am about everything.’

Weston was the natural, a pioneer and a comrade of the experimental and the progressive. A peer to Ansel Adams and a respected contemporary (though they never met) of Man Ray, Weston’s work moved from soft focus (and soft core) pictorialism favoured in America and Europe between the wars to something far more detailed, empathetic, sculptural and ultimately so perverse and pure that it can be seen as a precursor for the aspic qualities of the commercial pack shot or a surreal tendency for rendering the natural anything but.

Over two floors, a very good stab is made of encapsulating Weston’s five-decade career. From early nudes to the Mexican travels (which were to have a profound influence on him) to his landscape, vegetable and portrait work. Weston’s output was clearly phenomenal and to each new genre he brought diligence, precision and humour, whether he was expressing his inherent anarchistic sauciness in 1942’s ‘Civilian Defence (Nude with Gas Mask On)’, or showing the surrealists that if you want results you have to let nature get vaginal in the still stunning 1931 photograph ‘Shell and Rock Arrangement’.

If Weston has pushed the boundaries then dog-obsessed photographer, filmmaker and artist William Wegman has the privilege of not even seeing the line. Wegman’s thing is to create compositions featuring his own Weimaraner dogs in a variety of costumes and poses. Ideas of exploitation or cruelty quickly vanish as Wegman’s compassion and child-like humour emerges amidst the absurdia of many ridiculous scenarios. Wegman’s gift for comedy really comes into its own in his film work, the brilliant short segment films he made for Sesame Street aside. Wegman skewers the apple pie American dream with The Hardly Boys, a clean-cut tale of country pursuits and amateur detection featuring a cast of Weimaraner’s with human hands. It is the funniest thing you will see in any gallery, anywhere this festival.

City Art Gallery, 529 3993, until 24 Oct, £8 (£5).