The auditorium is a transverse slice of the whole cylinder with the seats steeply raked

The auditorium is a transverse slice of the whole cylinder, with the seats steeply raked so there are no heads between you and the 20-metre-by-26-metre screen wrapped around the curve of the opposite wall. A BFI person stands at a microphone, a small light shining on his face, and delivers a health warning which must surely be intended in part as a come-on. Carnival barkers down the ages have promised that their ride will give you a heart attack or turn your hair white. “Some people can find the Imax experience overpowering,” he says.

“If an image is too much for you, shut your eyes for a moment until the image changes.”And then you’re off on a ride which is a dizzy mixture of true grandeur and sudden bathos. Much of Destiny in Space was filmed in the early 1990s by astronauts aboard the space shuttle: the view from orbit has never looked so all-embracing, so vertiginously, truthfully world-sized. Across the foreground moves the cream flank of the shuttle, revealed by the fine analog grain of the film stock (no pixels here) to be an airframe bandaged over with many separate composite panels, without doubt a made thing, the fruit of ingenuity. Far, far above, so that you have to turn your head to see it, the blue-white limb of the Earth cuts across, its line a perfect arc which equally clearly belongs to a different order of creation. The cloud systems crossing the oceans down below have a feathery clarity. A view like this reminds you that “breathtaking” is a metaphor about the body.

When an image is this large in scope as well as in area on the screen, it squeezes a silent gasp out of you, like the collective “Aah” forced from our throats at a firework display. On the other hand, when the Imax is displaying things that aren’t intrinsically giant, the size of the image registers as a grotesque inflation, and anticlimax swiftly follows. I saw a simulation of the surface of Venus fly by, the red lines of mountains and volcanoes swollen with the gold light of upwelling lava; I also saw, when they interviewed the originator of the Hubble Space Telescope, a stringy, amiable 80-year-old expanded to become the world’s largest pensioner.The absurdity that’s generated when the Imax is working with images on the human scale has a straightforward perceptual cause, I think. The crucial fact is that the screen is larger than the central portion of your eye’s visual field – the section of your vision within which you can grasp things at a glance. More is always going on than you can immediately perceive the unity of You look around the image rather than simply gazing at it.

This is a very different regime from the one that usually obtains in film; and I imagine there’s another obstacle to Imax being used for a feature. It thwarts intimacy with the images on screen.Instead, Imax makes you react as to a panorama. It compels you to recognise, not just the size of the thing imaged, but your own scale in relation to it; metaphysically speaking, it is always placing you on the lip of the Grand Canyon. All of the South Bank Imax’s promotional literature emphasises the immersiveness of the experience. “You’ll float up into space, feeling the wonder of weightlessness .. ” But I’m not sure that’s right. As your point of view floats in low earth orbit, you don’t feel horror vacui, the fear of the emptiness around you, or even the milder fear that grips you when you’re swimming in the sea, and you come to a sensuous appreciation of the depth of dark water beneath you. You know that volcanoes of Venus will not burn you, the deserts of Mars will not freeze you.