Michael Bay once described his bombastic film-making style as “fucking the frame”, but if any director fornicates with the frame it must surely be Gaspar Noé, who blitzes us with flashing neon, 360-degree camera movements and intercourse closeups. So it’s a surprise when his new film, Vortex, begins with an elderly married couple (played by Françoise Lebrun and Italian horror maestro Dario Argento) sitting serenely on their Paris balcony. When the soundtrack plays a lovely Françoise Hardy song, you wonder if Noé has mellowed. But wait! If he doesn’t actually shag the frame here, he fiddles with it in two ways. First, the square-ish Academy ratio (1.37:1) of the serene prologue expands into a letterbox shape. Second, that widescreen divides into two side-by-side images, shot simultaneously with two cameras, enabling us to watch as Lebrun’s character, stricken by dementia, meanders around their cluttered flat, while Argento’s, wrestling with health issues of his own, nixes their adult son’s suggestion they move into a care home. Vortex could be Noé’s toughest watch yet – but this is due to its brutal honesty, and not because of the split-screen, which pays devastating emotional dividends. Most of today’s cutting-edge directors have at some point used split-screen sequences in their films. The effect still seems mildly adventurous, though it has been around since the birth of cinema. Lois Weber’s Suspense (1913) uses an innovative triangular split that still looks startling. In the last reel of Abel Gance’s 1927 epic Napoléon, the Academy screen opens out into three sets of film projected side by side to form a widescreen triptych. Split-screen was often used, with unobtrusive matting, to show one actor playing identical twins in the same frame, or as a witty ploy to sidestep censorship, making it look as though unmarried couples, such as Ingrid Bergman and Cary Grant in Indiscreet, or Doris Day and Rock Hudson in Pillow Talk, are sharing a bed rather than just talking to each other on the phone. Split-screen is perfect for phone calls: see Mean Girls. But as Guy Ritchie’s retro-styled The Man from Uncle reminded us, it’s an aesthetic we associate with the 1960s. Genius credits designer Saul Bass used split-screen montage for the opening of Grand Prix (1966); when Film Dope asked him about the technique a few years later he said: “I think it is terrific at expressing muchness, but I suspect it’s not capable of expressing deep feeling.” Bass’s split-screen is based on multiplication of a single image, but one year after Grand Prix, Christopher Chapman demonstrated his innovative “multidynamic image technique” in A Place to Stand, a landmark short made for the Ontario pavilion at Expo 67 in Montreal. (Earworm warning: I saw this film 50 years ago, and the maddening theme song has been lodged in my head ever since.) Chapman presents multiple panes in various sizes and shapes on a single screen; sometimes the images in the panes move independently, sometimes as components of one big picture. Steve McQueen saw A Place to Stand at an advance screening in Hollywood and was impressed. One year later, Norman Jewison inserted split-screen sequences into The Thomas Crown Affair, including the opening credits, and McQueen playing polo. That same year, in The Boston Strangler, Richard Fleischer divided his screen to show a creepy phone caller, the recipient of the call, and the call being traced, all at once. Spilt-screen enabled Michael Wadleigh, director-cinematographer of Woodstock, to show crowd reactions in the same frame as the performers, while in 1973, Soylent Green employed it in the opening credits to encapsulate the “muchness” of proliferating industrialism and pollution. The director most associated with split-screen is Brian De Palma, who turned it into an operatic art form. In Sisters, he shows the point of view of a dying murder victim at the same time as a witness looking back at him, and in Phantom of the Paradise he ramps up tension between the planting of a bomb and its explosion. Many mainstream audiences encountered split-screen for the first time in Carrie, when the traumatised antihero wreaks telekinetic carnage at her prom. De Palma told Cinefantastique magazine: “I felt the destruction had to be shown in split-screen, because how many times could you cut from Carrie to things moving around? You can overdo that.” But split-screen all the way through a film? In 1966, Andy Warhol and Paul Morrissey conceived Chelsea Girls as a six-and-a-half hour experimental film, before dividing the footage and projecting two contrasting images side by side in a three-and-a-quarter hour film. The 1973 psycho-thriller Wicked, Wicked, directed by Richard L Bare, was filmed almost entirely in “Duo-vision”: the widescreen divided into two and showing not just murders from the point of view of both killer and victim, but also flashbacks to the psychopath’s childhood, creepy Bava-esque corpses, and a random organist playing music from The Phantom of the Opera. Results range from lame to preposterous, so clearly this is a cult film waiting to happen. The most ambitious split-screen project to get a more-or-less mainstream release, and certainly one of cinema’s more enjoyable avant garde experiments, is 2000’s Timecode. Writer-director-editor Mike Figgis satirises his own experiences in Hollywood with four sets of footage, shot simultaneously by four cameras and displayed on a screen divided into quadrants showing two dozen actors improvising around a predetermined story about a film company casting its new production, The Bitch from Louisiana. Noé’s other format-related gambit in Vortex – opening out from a square screen into a wide one – is already something of a cliche. Most filmgoers of my generation first became aware of aspect ratio thanks to the abomination of pan-and-scan, in which TV companies in the 1970s and 1980s routinely cropped films to fit 4:3 TV sets, thus reducing the climactic shootout in the widescreen Once Upon a Time in the West to an expanse of blue sky and the edge of someone’s hat brim. That was before the advent of DVD and widescreen televisions. Nowadays TV networks tend to err in the opposite direction, reformatting 4:3 shows such as Friends or The Wire to fit widescreen sets. But aspect ratios can and do coexist in harmony. Back in 1956, Tom Ewell commanded the edges of the frame to slide further apart at the start of The Girl Can’t Help It, easing his 1950s audience into what was then a relatively unfamiliar widescreen format. Since then, the expanding screen has been used many times to signify the passing of time or a shift in location, from Mad Max 2 and Galaxy Quest to Oz the Great and Powerful and Valerian and the City of a Thousand Planets. And digital technology has made format-switching easier than ever. Wes Anderson uses different screen ratios to signal three different eras in The Grand Budapest Hotel. In the intimate sci-fi drama After Yang, writer-director Kogonada switches between three different aspect ratios (two of them can be seen in the trailer) in a more subliminal way to differentiate between everyday life, video calls and memories as a family struggles with feelings of bereavement after their “technosapiens” (androids) breaks down. Attempts to woo audiences back into cinemas with 3D or Imax (itself a square-ish format, albeit a gigantic one) have overshadowed a quiet sea change further down the budgetary scale. After decades of widescreen (1.85:1 or 2.35:1, for example) as the norm, the squarer Academy ratio has been making a comeback, with film-makers such as Kelly Reichardt (First Cow), Paul Schrader (First Reformed), Joel Coen (The Tragedy of Macbeth) and Paweł Pawlikowski (Cold War) making it the arthouse director’s format of choice. Some have gone even further: Robert Eggers’ The Lighthouse is in 1.19:1, while Xavier Dolan’s Mommy (2014) was filmed in a perfect square. “The character is our main subject, inescapably at the centre of our attention,” said Dolan, and it does indeed appear to signal an intent by film-makers to distance their work from an increasingly homogenised cinema of widescreen spectacle. Can the frame be squeezed even further, perhaps reflecting the way most people film with their smartphones? I’ve yet to hear about an entire non-experimental feature in a vertical format, though, in his short The Stunt Double, made for iPhone, Damien Chazelle presents an amusing alternative history of cinema genres filmed that way. Just as sex never falls out of fashion, so film-makers’ appetite for frame-fucking seems impossible to quench.