IMAX and 70mm, explained: which formats are actually worth going out for

Two names get used to justify a more expensive ticket, and they describe different things. 70mm is a film stock. IMAX is a system — cameras, projectors, screens, sound and a certification programme. Knowing the difference is the whole of knowing whether a screening is worth travelling for.

What 70mm film is

Standard cinema film is 35mm wide, measured across the frame. 70mm is roughly twice that, which means a much larger negative, more detail, less visible grain and a bigger, brighter projected image. It was the premium format of the mid-century epic — the format the roadshow musicals and the widescreen spectacles were photographed on — and it effectively died as a production format when digital intermediate post-production took over. It survives now as a deliberate choice: a small number of directors shoot 70mm because the image has a specific texture, and a shrinking number of cinemas can still project it. A genuine 70mm print screening is a rare event, and the rarity is the point.

What IMAX actually is

IMAX began as a large-format film system using a 15-perforation 70mm frame running sideways through the camera, producing a negative several times the area of standard 35mm and a projected aspect ratio of 1.43:1 — dramatically taller than any other commercial format. That is the version people mean when they talk about the IMAX image: more picture above and below, not just a bigger screen. Alongside it, IMAX developed digital projection, and most IMAX-branded screens today are digital rather than film.

The distinction that matters at the box office

There is a real difference between an IMAX screen and an IMAX experience. Digital IMAX installations commonly project at 1.90:1 on screens that vary considerably in size, and some venues branded IMAX have modest screens with a capable projector and a good sound system. The 1.43:1 expanded image only exists where the venue has the dual-laser or 70mm capability to show it. So the same film, on the same release, can genuinely expand the frame in one city and simply look bigger in another. Cinema listings usually specify the format; where they do not, the screen's own specifications are worth thirty seconds of checking before you buy.

Which films expand the frame

Only films shot with large-format cameras have extra image to show. A production that shoots its action sequences with IMAX cameras and the rest with standard ones will present those sequences taller; a film shot entirely at 2.39:1 on a normal camera gains nothing on a big screen except size and brightness, which are real but different benefits. Directors who commit to the format shoot entire features into it, and those are the screenings where the format changes what you see rather than how big it is.

The honest guidance

Travel for the format when a film was photographed for it and the venue can actually show it; that combination is genuinely different and increasingly rare. Otherwise the bigger question is the room: a well-maintained screen with correct projection geometry, good sound and no obstruction beats a brand name in a cramped auditorium every time. Format is a reason; it is not by itself a guarantee.