IMAX Enhanced: IMAX Comes Home

IMAX, as most people experience it, is a high quality movie format used in specialized theaters worldwide. But its history, and development, is complicated. I'll provide only the Cliff Notes version here, as our primary subject is a relatively new home theater format that trades on the IMAX name.

IMAX was first developed roughly 40 years ago for special venues in museums and science centers. The programs there were filmed documentaries, generally running one hour maximum with titles such as Blue Planet and Africa, The Serengeti. Apart from its educational and entertainment value the main attraction was spectacular technical quality in both picture and sound. The screens were immense, sometimes as much as seven stories tall, the aspect ratio 1.43:1, and the resolution, as captured and presented on 70mm film (this was well before the advent of digital cinema), offered a picture area nine times larger than the 35mm used for theatrical films.

But IMAX installations were few and far between. This included a variation called Omnimax, which presented the films on a dome-shaped screen. I visited one the of the latter at Caesars Palace in Las Vegas during many a CES, but it was demolished years ago (the Omnimax, not Caesar's Palace).

Today there are about 1,500 IMAX screens worldwide. But most of them are very different from those original IMAX theaters, and the majority of them present theatrical films. The screens, while still large, are far smaller than before since they had to be adapted to fit in the largest multiplex auditoriums. The aspect ratio is now 1.91:1 rather than 1.43:1 to better suit dramatic films. Most IMAX theaters now use 2K digital projection rather than 70mm film — often two digital projectors synched together, their images overlaid for a brighter picture (or used differently for 3D). (Upgrades to digital 4K were in the works for many IMAX theaters, but most have been delayed due to Covid's disruption of the theater market.) Where 70mm projectors are still installed they likely gather dust apart from special presentations.

While digital projection offers nowhere near the theoretical resolution possible from 70mm film, apart from being more economical it does have advantages of its own. For one, there's no wear from multiple showings. Digital projection will look the same on its 50th showing as on its first, while film will not. Technically savvy filmgoers who wanted to see a new flick in the film era at its technical best went on its opening weekend.

In any event, full-up IMAX was never going to be financially viable for hundreds of theaters. And until the recent introduction of the superior (for me), Dolby Cinema theater installations, even this stripped down IMAX was by far the best way to see a movie at your local multiplex. Dolby Cinema even now has far fewer theaters than IMAX, so the latter remains the best game in town for many theater fans.

Enter IMAX Enhanced
Introduced to the market about three years ago, IMAX Enhanced is a home theater format rather than a theatrical one. A co-development by IMAX and DTS, it claims to offer upgraded video and audio performance. But the reality here is complex.

The video side of IMAX Enhanced has grabbed much of the attention. As you may or may not know, IMAX commercial theaters can present films in one of three ways, depending on how they were shot. On some films most of the movie is conventional 2.39:1 widescreen, but for greater impact it opens up to the full theatrical IMAX aspect ratio of 1.91:1 on selected scenes. While the width of the picture remains the same in both formats, the IMAX image is substantially higher vertically. If the 2.39 screen is 20-feet wide (kind of big for a home screen, but we'll run with it as an example!), the 2.39:1 scenes will be 8.5 feet high (20/2.39) in conventional widescreen with black bars at the top and bottom. But in the IMAX scenes the images will be 10.53 feet high (20/1.91) with no black bars. Isn't math fun!

In the second form of an IMAX presentation, a film simply uses 1.91:1 throughout. And in the third variation it simply uses 2.39:1 for the entire film. We'll ignore the latter here; it isn't truly IMAX, but a commercial IMAX theater might still present such films to take advantage of the theater's superior sound (and higher ticket price!) if an IMAX film isn't available.

In the first format listed above, the one that IMAX Enhanced is primarily concerned with, the bulk of the film will be 2.39:1, mixed with selected 1.91 scenes. A film transferred to video this way will show the two types of scenes at home much as they appeared in the theater.

But if the film is transferred with its full-screen scenes at 1.78:1 (to match the aspect ratio of current TVs) rather than the original's 1.91:1, some vertical cropping will be required in the video transfer. Using the math above, 20/1.78 = 11.24 feet — too high to fit on that 1.78:1 screen.

Cropping the original 1.91:1 aspect ratio in the originally filmed expanded scenes to 1.78:1 during the video transfer does the trick, but inevitably deletes small slices of the image at the top and bottom. The loss will be irrelevant, but perhaps troubling to some. You can regain those few silly mm of information in the video transfer by expanding the vertical image to include them, but in doing so you'll then lose a few mm in the width, resulting slender black bars at the sides. Your screen is still 1.78:1 with all of the limitations that involves; there's no free lunch here, and the screen width is a constant.

Even prior to IMAX Enhanced, some video releases were offered this way and required nothing more than a 1.78:1 screen to enjoy them. That hasn't changed, but the major advantage of the IMAX Enhanced format is your assurance that the dual aspect ratios in the original theatrical presentation are retained in the IMAX Enhanced video release.

The promotions for IMAX Enhanced put great emphasis on the claim "more picture without the black bars," this is profoundly misleading for the fledgling videophile, given that the presence of black bars sacrifices no video information on most conventional widescreen films. But the format offers other claimed audio and video benefits as well. Nevertheless, there shouldn't be any "improvements" in the basic audio and video quality beyond what you'd get from any other good video release of the same film, assuming (in the latter case) competence on the part of the technicians performing the video transfer and adherence to the filmmakers' intent.

IMAX Enhanced also sets standards for the audio and video on an IMAX Enhanced release, but as with the now ancient THX standards these haven't been released to the public and will likely remain undisclosed except to IMAX Enhanced licensees. But on the upside, the extra layer of oversight IMAX Enhanced offers in the audio/video transfer stage can't hurt.

On the audio side all IMAX Enhanced releases offer DTS:X, DTS' answer to Dolby Atmos object-based audio. There are also other vaguely described "enhancements" to both audio and video in the IMAX Enhanced format, plus an IMAX Enhanced mode in TVs and AVRs that carry the IMAX Enhanced logo. Some of these TVs and AVRs are or will be designed to automatically switch to the IMAX mode when the device senses the presence of an IMAX Enhanced source. But any benefits to an IMAX Enhanced source should be visible and heard on any competently set up home theater with a 1.78:1 display without the need for any such mode. You shouldn't need to toss your TV and/or AVR to view and hear IMAX Enhanced material. And hopefully it will be possible to defeat any "enhancements" offered by an IMAX Enhanced mode, just in case, should your gear offer it.

To repeat, the major benefit to the IMAX Enhanced label on a disc or stream is that it ensures that the release retains the varied aspect ratio if present in the original IMAX source. But since there are very few such films (a minority even of IMAX presentations), IMAX Enhanced might feel the need to release films that were originally IMAX but type 2, as discussed earlier — with a consistent IMAX aspect ratio throughout.

It's too early to judge exactly what IMAX Enhanced will mean to the industry. Is it a viable format or merely an attempt by IMAX and DTS to grab back a share of the home theater market they've lost to Dolby formats in the last few years (DTS dominated the audio tracks on pre-UltraHD Blu-ray discs). As I write, however, there are still very few IMAX Enhanced video releases available on either UltraHD Blu-ray or streaming — a total of under 25 by my count in mid-December 2021. But keep your ears to the ground and your eyes on bars.

Billm's picture

Good article, good info, much appreciated!

And I agree with it, not that that means much [-;


Traveler's picture

So is this 8k or 4K UHD? What streaming services offer it, I don't see it on my Roku Ultra?

Thomas J. Norton's picture
On your first question, it should be 4K. There's no consumer source material of any kind, or from any source, that's 8K. Nor is there any movement that we're aware of to offer native 8K to the general public, either at home or in the theater. The data space required is huge and the demand nonexistent. Also, as you may be aware, the CGI special effects that are widespread in today's films are typically rendered in 2K. There are consumer 8K video displays available, of course, but they rely on upconversion of lower resolution sources (4K or lower) to fill all of their 8K pixels.

All of the streaming IMAX Enhanced sources today that we know of are (some but not all) Marvel titles available only on Disney+.