One of the best things about a Cindy Sherman show is you never know what you’re going to get. And in this exhibition, of a new series of "Untitled" images, what you get is very surprising indeed. Sherman's photographs are not about her, but they are always her. Sherman has always used herself – or "herself", a manipulated, redacted representation – as the canvas on which she works. This time, however, the canvas itself has changed.

A well-groomed, middle-aged woman walks into view and lights a cigarette. She stands, she smokes, the camera gives us a steady close-up of her face. As she appears to reminisce, her face subtly registers a range of emotions. Is she agitated, sad, irritated? She takes long drags of her cigarette. The film ends and she walks out of view. A second film begins. Same woman, same duration. A cigarette is smoked, the camera lingers on her face. She’s lost in recollection, but wait, there are subtle changes. A different backdrop.

Oh dearie, dearie me. Modern Perspectives sounded like it had such promise. Running alongside the big Canaletto show in the Sainsbury wing of the National Gallery, two finished works and one work in progress by Ben Johnson are on show in Room One. The idea is to look at a contemporary artist who, like Canaletto and his coevals, produces panoramic views of cities. Johnson, despite his quasi-illustrative, photo-realist style, says he produces not "topographical representations of a real place, but perhaps a manifestation of a dream... timeless and transcendent". Wouldn’t it be pretty to think so?

Simon Starling’s wonderfully eccentric exhibition Never the Same River (Possible Futures, Probable Pasts) will inevitably mean more to those who have visited the Camden Arts Centre regularly over the years. Places gradually acquire a patina of memories that accumulate layer on layer and infiltrate one’s perceptions in the present moment. Travelling round London, I encounter my past at every corner – the Slade where I spent many hours drinking coffee before being gripped with ambition to become an artist, University College Hospital where I gave birth, the house where I discovered how hard it is to be an adult, the doorstep on which a former lover confronted a future one, and so on.

Norman Rockwell’s America. What did it look like? At the height of Rockwell’s incredible fame as an illustrator, you might say it looked a lot like a movie still. Think of the films of Frank Capra, for instance: heartwarming scenes of family life shot through with poignancy as well as humour. This vision came with an instinctive appreciation that the most precious things we have in life are also the most transient and fragile. It’s a vision that clearly comes with a sense of empathy for the common man, an empathy that elevates his American everyman into the heroic figure of home and hearth.

As I wandered round this year’s New Contemporaries at the ICA, a few yards away in Trafalgar Square, thousands of students braved the cold for the third time to protest against the Government’s proposed spending cuts on education. How many art students joined the rally is impossible to tell, since most London art schools have been swallowed up by universities and lost their individual identities in the process. Whereas the high-profile sit-ins of 1968 were orchestrated by students from Hornsey College of Art (now part of Middlesex University) and, 20 years later, students from Camberwell College of Art (now part of the University of the Arts, London) were leading vociferous protests against cuts in art school funding, any art students involved in the current unrest are all but invisible.

A retrospective at Tate St Ives can be a poisoned chalice for the major artist. It postpones his or her prospect of a showing at Tate Britain by a couple of decades, and can appear to consign them to the comfort zone of "Cornish Art": the heritage Modernism of Barbara and Ben, Terry Frost, Patrick Heron et al, stuff we love (well, most of us) because it reminds us of being on holiday, but may feel, in our heart of hearts, to be more than a touch minor. On the positive side, Peter Lanyon, who was killed in a gliding accident in 1964, isn’t around to mind, and there’s something to be said for being able to look from one of his lyrical canvases straight out at the surf crashing on Porthmeor Beach and the edge of the windswept, ancient landscape Lanyon regarded as his personal Calvary.

The thin line between Art and Craft gets slimmer as artists like Carlos Zuniga ignore the borders and delve into hands-on production processes. This Chilean photographer, architect and graphic designer works compulsively on large, imposing portraits and landscapes using intensely obsessive techniques.

Lovers of the beautiful game may already be familiar with the name Philippe Parreno, or at least with his best-known work. In 2006 he collaborated with artist Douglas Gordon (24-hour Psycho) on Zidane: A 21st-Century Portrait, a film that trained 17 cameras on the footballing genius for the duration of a game. Following Zidane’s every move, the 90-minute feature proved an especially intimate portrait: the cameras stayed close, never straying, never hinting at the 80,000 strong crowd nor bringing the other players into view. Zidane, who was also miked up, appeared oblivious to the intense scrutiny of the multiple lenses; it was a portrayal of a man utterly, unselfconsciously focused on what he was doing.

Well, we all make mistakes. Or, in my case, we (I mean “I”) sometimes just fail to look. This new, small but perfectly formed exhibition of Bridget Riley’s work in the National Gallery’s Sunley Rooms follows the pattern that the gallery has developed over the years, with a single artist entering into a conversation with the great art of the past. Riley’s conversation is gripping, and one of the things it says (to me) is, “Shame on you for not looking.”