The IMAX we grew up with it 70mm 15 perf:

--Type: 15/70
Originally developed by Imax Corporation in 1970, this format uses 70mm film run through the projector horizontally, so that the width of the film is the height of the frame. In all other LF and conventional formats, the film runs vertically, so that the width of the film is the width of the frame. Each frame is 15 perforations wide, hence the term “15/70.” The area of the frame is about 52mm high by 70mm wide (2 inches by 2.75 inches). The 15/70 frame is almost nine times larger than the conventional 35mm frame (below). It is slightly less than twice as large as 8/70. Imax Corp. was long the exclusive maker of 15/70 projectors and cameras, although a few other manufacturers briefly made 15/70 systems.
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^^New films are not being released in this format - but you can see older films in this format if your local theatre didn't uninstall the old system, Hint:They uninstalled it.



--Type:IMAX digital
Imax Corporation introduced its first digital projection system in 2008, using two Christie 2K projectors and proprietary image processing. (Later systems were manufactured by Barco.) With an aspect ratio of 1.9, this system was designed to be installed in existing multiplex auditoriums. IMAX digital projection system
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^^That's Lie-MAX.

--Type: IMAX with Laser
In 2015, Imax began the rollout of its first laser projection system, which it labeled “GT” (confusingly, the same term it had used for its largest 15/70 film-based projectors). It uses two custom-designed 4K laser-illuminated projectors, based in part on patents purchased from Kodak, and built in partnership with Barco.

It has an aspect ratio of 1.43, achieved with a vertical anamorphic stretch of the standard 1.9-ratio 4K image. It is designed to replace 15/70 film projection in the largest IMAX theaters, with screens over 80 feet (24 meters) wide.

In 2018 Imax introduced a 4K laser system for dome theaters, based on a single GT laser projector, as seen at the right. It has the same 1.43 vertical anamorphic stretch as the two-projector IMAX flat-screen laser system. The projector is placed in the center “doghouse” position of the dome, on an elevator, similarly to the film projector it replaced.

Unlike most other digital projectors, these systems are not capable of frame rates higher than 48 fps, and can only achieve 48 fps by dropping down to 2K resolution. Reportedly, Imax has no plans to upgrade these systems to higher performance standards.
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^^That's LIEMAX-lite. But much better than Imax digital. Nto as much detail as "real IMAX" but probably brighter.

And there's formats like 65mm/6 perf, whcih while not IMAX, is a large format stock. Tenet was shot on this. I think it was release on 70mm/5 perf too (upsized.) 5/70 is the old, non IMAX, large format we've all seen.

I'll se it at 16:9 like 99% of the world will and just ignore the IMAX release.