Until I visited the National Portrait Gallery’s “Cindy Sherman” exhibition – it runs until 15th September – I had been only dimly aware of the celebrated American photographic artist. Was she important? After all, she has spent her career photographing – herself.

On the face of it, that’s posturing self-indulgence. #MeMeMe. Not my thing. True, many artists love self-portraits. Rembrandt knocked off forty; Van Gogh thirty, plus or minus a left ear. Sir Stanley Spencer’s final self-portrait is one of the most compelling, honest, paintings I‘ve ever seen. What’s this common obsession with “self” for?

A private reminder, maybe, of the passage and ravages of time? So, should we be gawping at these “memos to self” at all? Often they are frank, but private self-admonitions – Rembrandt’s especially. Tempus, in the form of an increasingly bulbous nose, certainly fugits. Maybe they were never intended for us. Private contemplation only.

Cindy Sherman is a paradox. Not a single photograph in her oeuvre of self-portraits spanning forty years is of “her”. They are all of her as other characters. And therein lies her genius. Obviously, she likes her Hamlet: Polonius to his son, Laertes; “For the apparel oft proclaims the man”. Make-up, clothes, prosthetics always adorn Cindy Sherman, the chameleon.

She has dedicated her career to illustrating why we don visible armour, to tell the world what we would like to be, while unconsciously revealing the cracks in our self-conceived images. Ms. Sherman’s work is a powerful purgative for conceit.

Her oeuvre falls into definitive “periods”. In the early eighties, she kicked off with “Untitled Film Stills”. One set stands out; a sheet of small headshots showing a transformation from gawky pebble-glassed kid to provocative “come and get me” vamp. All achieved by conscious artifice.

“Rear Screen Projections” followed in 1981. She uses the technique of presenting her close up subjects against a projected backdrop. The result is ambiguity. There’s “stuff” going on in the subject’s eyes and body language, and “other stuff” going on in the background – countryside flashing past seen through a bus window, a telephone that either hasn’t rung – or perhaps has, then been slammed back into the receiver. Who knows which?

Aside for millennial, snowflake readers: A telephone receiver is the handheld part of a communication device called “the telephone”, used long ago to allow people to speak with each other over great distances, by means of copper wires. The body of the device incorporated a “dial”, on a return spring, which featured finger holes, each representing numbers and – bafflingly – three letters of the alphabet.

You picked the hole with the number you wanted, turned it to the right and a Mr. Strowger, sitting in a building some way off, would connect your wires to the wires of the telephone whose number you had just dialed. Mr. Strowger is Alexa’s great grandfather. The first dial telephone was discovered by Howard Carter in Tutankhamen’s Tomb in 1922…

Later came “Centrefolds”, commissioned by Artforum magazine, but never published, as the depictions were so challenging. Clad in high fashion, the subjects – all Cindy of course – came across as vulnerable, ambiguous and conflicted, exhibiting none of the infantile certainty of conventional fashion plate models. For me, that makes for a far more compelling image, but Artforum was afraid of kicking over the traces of convention.

“Pink Robes” discarded cosmetics and props and focused on a pink bathrobe, for the first time the subject looking directly, challengingly, at the camera. The intention was to represent the guarded psychology absent in pin up photography. These were all models between shots. This is probably the most “beautiful” of her series – and closest to her own persona.

“Color Studies” saw Ms. Sherman return to disguise, this time using ordinary characters with anything but “ordinary” back stories. I guess she is a fan of Edward Hopper, the early 20th century artist who specialized in moody studies, “Nighthawks”, being the most iconic, in which the subjects, remote from each other, pursue their own, often unfathomable agendas. The satisfaction comes from the speculation as to what the hell is going on.

The series of “Fashion” photographs from 1983 – 84 are harsh and shocking. Ugly, often troubled women represented in a parody of the conventional, glitzy advertising shots of the time. Here, clothes clearly do not make the woman. And, that’s the point. Reality will out. What is bizarre is that fashion houses still commissioned Cindy Sherman – in spite of her refusal to acknowledge that their products are the panacea they persist in peddling.

Towards the end of the eighties, Ms. Sherman’s eye was caught by the visual language of old master paintings. In the “History Portraits” she conscripted a veritable army of devices, prosthetics, false noses, breasts and skullcaps to depict thirty-odd historical figures, women and, unusually for her, men, mostly in Renaissance poses.

I’m not sure what to make of these, other than to acknowledge the point that artifice is no recent refuge for a sitter. If Ms. Sherman can turn herself into a convincing Erasmus, maybe there’s hope for us all. We have tried to be other people for centuries.

The rising tempo of media vulgarization and the dropping of any inhibitory veil from sexual subjects as the internet rolled out in the 90s, led to “Sex Pictures”, “Fashion” and “Surrealist Pictures.” These are truly disturbing, using dolls – often mutilated – mannequins, and prosthetics to parody internet pornography, in all its de-humanising detail.

They are the only series in which Cindy Sherman betrays real anger through her work. Elsewhere she deploys quizzical humour. Here, she trumpets a clarion warning – and, uniquely, can’t bear to use her own image to make her point. The mannequins do the work.

The National Portrait Gallery exhibition is comprehensive on the span of Ms. Sherman’s photography, but falls down in all but ignoring her films. There is one, tiny, rolling video display of an early work. Film was – and is again becoming – an important aspect of her work. Pity it was sidelined.

And, dammit, there is sparse detail provided. No accompanying catalogue. No audio guide. If dropping in unprepared, the viewer would be – frankly – baffled. Who is this woman who portrays herself one minute as a film extra, then a fashion plate, on to a clown, ultimately a fragile society figure? I found myself humming “What’s it all about, Alfie?” as I wandered about – sotto voce, you’ll be relieved to hear.

I had a crib, so some idea what to expect. I highly recommend watching, while you still can, a BBC Arena programme, “Cindy Sherman#untitled” on iPlayer, available for another two weeks. (Why does the Beeb time limit interesting programmes like this and keep boring rubbish about steam engines manned by sweaty-ragged footplate men running forever?) This one expires in 14 days.

The programme contains rare footage of Ms. Sherman being interviewed, occasionally through the medium of her spokesanimal, Mister Frieda, a fashionably gender-fluid, protective, green Macaw parrot. It’s essential viewing if you’re going to the show.

If the point of art is to change our view of the world around us, open new doors of perception, the Cindy Sherman exhibition will not disappoint. It will be difficult to look at a fashion plate ever again without wondering what lies behind the veneer. She is whimsically cheerful, taking her art seriously – but never herself. If Mister Frieda ever let you into her studio I bet it would be fun. “Hand me that prosthetic nose”!

Nowadays she maintains an Instagram Account with 272,000 followers, on which she plays distorting fun and games with Apps that age or rejuvenate at the touch of a button. I have a feeling the tech world is just about catching up with the ever elusive Cindy Sherman.