Perhaps, though, the dominant personality here is one that does not appear in Messager's own listing - over the past 40 years - of her assorted selves. After experiencing Casino, which has a doorway framing a wave of rich red silk that suddenly swells and billows towards the viewer, and Inflated-Deflated, a floor covered with pulsing and swelling fabric body parts and sea creatures, the abiding impression is of Messager as, above all, a fairground impresario.

The German artist Gerhard Richter also works in a variety of modes and is regularly hailed as the world's most important living artist. Last year, he was at the Serpentine Gallery in his most anodyne guise with a display of colourful, pixelated grid paintings; now he is at the National Portrait Gallery with a fine retrospective of his mesmeric portraits.

The basis for all Richter's art is his unease with perceived reality: the senses, he believes, project the world imperfectly and are therefore not to be trusted. As a result, he claims to have developed a very unpainterly thing - a loathing of subjectivity. His solution is to bypass the senses and base his work on photographs instead.

This exhibition contains some 35 portraits from the 1960s onwards and, unlike the celebrities favoured by Andy Warhol, they are mostly of anonymous sitters whose images he found in magazines or of family and friends taken from snapshots. He expanded and transcribed these photographs on to canvas before gently blurring the entire surface with soft horizontal strokes of the brush. By doing so, Richter notes, "Something new creeps in, whether I want it to or not."