IMAX: bigger is better (Part 2)

There’s one word that is synonymous with giant screens: IMAX. Grant Lobban investigates the impact it has had on Premium Large Formats


Although it had its origins in the special venue side of the industry, screening educational films at exhibitions, museums and similar institutions, IMAX would eventually take a similar path to 3-strip Cinerama to attract a wider audience by showing more normal ‘entertainment’ films on its giant screen.

First seen in 1952, Cinerama’s  earliest features included a series of travelogues  resenting exotic locations. Once the format had run out of places around the world to visit, the 3-strip system was used for a couple of story films. Although one, How The West Was Won, was very successful, most film-makers weren’t prepared to be restricted by its fixed 146-degree angle of view. An important factor in giving its sense of involvement, the switch to the narrower views of 70mm increased the range of films to show, but lost some of the original magic.

Features, such as Grand Prix and 2001, suited curved screens, but to make the most of others intended for an initial Cinerama release, their widest possible camera lens was fitted to include an occasional ‘Cinerama-type’ sequence. Some were at the start to show off the screen, as in The Battle of the Bulge which featured a hold-on-to-your-seat flying sequence over the battle and Khartoum which set the scene with a mini- travelogue taking in ruins of ancient Egypt.

Seen first in 1970, IMAX’s own efforts to broaden its appeal benefitted considerably from the birth of the digital age. They developed their DMR (digitally re-mastered) process for blowing up 35mm films to its 70mm 15 perf. frame. The negative is scanned at the highest possible resolution, the image ‘optimised’ for the big screen, and transferred onto the film print.

To bring them to more theatres, a simpler more compact projector, with moving rollers replacing the compressed air to form its rolling loop, was built to fit in alongside their normal projectors. Space also had to be found for the 6ft platter carrying up to 9 miles of 70mm film now needed for the average full-length feature. The auditorium was sometimes re-styled with new, steeper stadium seating to ensure a good view of the screen, which isn’t as tall as the original, but most DMR copies from ’Scope and widescreen films don’t fill the complete 4:3 IMAX frame.

The next step, which would see the IMAX name feature on many more multiplexes, was to show its optimised image directly using digital projectors. Without IMAX film frame size DLP chips available, to reflect the amount of light required two projectors superimpose a pair of auto-aligned images on the screen to achieve sufficient brightness. They are also available to project separate left and right eye images for 3D, and a further move to replace xenon with even brighter laser illumination has allowed the previous polarised filters to be replaced with a less light-hungry spectral splitting colour separation system. The shape of digital IMAX is 1.9:1, making the best use of the full area of current DLP chips. If possible, today’s films, originated on both 35mm film and digital, are re-formatted to fit, but if they keep their original ratios they can leave much of the vast unmasked screen blank.

Keeping bigger, looking better

On typical size screens, digital projectors are producing excellent pictures, which for many are just as good, and more consistent than film. However, without the advantages of the larger 70mm and IMAX film frames, their nearer to 35mm size 2K and 4K chips are being pushed to fill the new PLF giant screens. As well as a pair of projectors working together to maintain the same level of illumination, some also add extra visual tricks and artefacts to their images to keep them looking good and help them to stand up to the greater magnification and closer viewing distances.

Film vs digital

In terms of definition, even 4K is less than 35mm. A recent comparison suggests that a ‘Scope frame is around 6K, 70mm (from a 65mm negative) is 12K and the original IMAX film 18K. Arriving at an exact figure is complicated by the fact that film and digital record and display their images in a different way.

Unlike digital’s fixed pattern of pixels, film has the benefit of its moving grain, with a better chance of capturing the finest detail, if missed by one frame it may be picked up by the next. A hint of visual grain can also make film appear sharper. It’s all in the eye of the beholder, but some 70mm lovers think that it’s not like it used to be, blaming modern film stocks for being too good, with their grain-free velvet texture lacking the punch and sparkle remembered from the past. Although high definition is important, particularly for extra large screens, it’s only one factor in producing good quality pictures. A phenomenon that the latest HDR systems exploit is the well known observation that a well-lit picture with a wide contrast range can ‘look’ much sharper than a higher definition one that has a dim, flat, lower-contrast image.

On the edge

Some film processing methods accentuate an edge effect with increased contrast just along the edges of the image, which again adds to the apparent sharpness (denser parts steal some of the developer’s strength from the edge of adjoining lighter exposed areas). Video and digital also have their own versions to make their finer detail stand out. SD video often puts a white line around it, and one form of digital ‘definition intensification’ increases the relative contrast between adjacent pixels along the boundaries, with the amount applied depending on the nature of the image.

Looking for something different

Film and digital can offer different viewing experiences. Some think that digital lacks some of the ‘magical’ look of film and is more like watching big screen TV in the dark, even more so with the prospect of large active LED cinema screens.

Back at home, analogue audio is making a comeback, with today’s digital generation willing to put up with the odd click and plop from their ‘new’ vinyl records in exchange for the chance to hear a less clinical, more friendly sound coming from their speakers. Perhaps now is a good time for them to re-discover the different look of analogue film projection and encourage them to make a journey to see a special edition’ 70mm show once more?

Fortunately, real film lovers, like Christopher Nolan and Kenneth Brannagh have helped keep 70mm and IMAX film alive, while waiting for a wider revival. Apparently, other film-makers are waiting in a queue to use Panavision’s remaining Super 70 65mm cameras, and the search for new old 70mm projectors continues, together with the skills to run them. Often their refurbishment doesn’t include the sound head, as new 70mm films can no longer be accompanied by the appropriate analogue sound. With the print’s magnetic stripes now long gone, the sound is coming from a separate digital source. At best, with digital cinema firmly established, 70mm may find a place as another form of event cinema, recreating the memorable roadshows of the past.

The screen’s still the thing!

While 70mm remains an occasional treat, many more multiplex auditoriums are being turned into digital IMAX and other Premium Large Format screens. There currently don’t appear to be any minimum requirements to gain the title, such as the size and shape of the screen, or how much it should fill the audience’s field of view. In practice, most feature increasing the size of the screen relative to that of the auditorium and arranging the ‘premium’, sometimes motorised, reclining seats so every member of the audience can appreciate it. To rival IMAX, it should be wall-to-wall and floor-to-ceiling. This can be a challenge for designers, sometimes having to raise the screen so those in retained, original shallower seating can see the bottom of the screen. Sometimes, a section of the screen has to be moveable, in case now-covered emergency exits in the front wall are needed.

The new giant screen can dominate the auditorium. Those who can still remember entering an old Cinerama theatre, with their vast curved red curtains, find being confronted with a looming plain giant flat screen less welcoming. At least one IMAX theatre is said to have fitted equally huge curtains to give it a less ‘cold’, more theatrical ambience.

Some of the first digital PLF systems struggled to maintain the same rich and sharp image, but recent technology, including HDR and laser light sources, have helped them to keep up with the growing screen sizes. Both film and digital cameras are capable of much higher resolutions, but the final screen image is limited by the projector’s pixel count. When asked to fill bigger than normal screens, the resulting pictures could be compared to the earlier 35mm films blown up to 70mm, with a good, bright larger image, but without its full potential.

And The film’s the thing too

The success of a PLF screening can depend on the film’s subject matter and style of photography. Plenty of action and all-embracing wide shots can add to the excitement and help draw the audience into the heart of the story. However, quieter, more intimate stories, can end up with a rather distracting over-blown look, with in-your- face close-ups better observed from a little further away with less visual intensity. For the leading systems, the choice of suitable films also involves the film-makers and distributors. IMAX, for example, currently produces its own DCP, incorporating its optimised image, which may have been re-formatted to make the best use of the screen. Another, Dolby Cinema, hides Dolby’s own enhancements, including its Dolby Vision version of HDR, within the normal DCP, which, looks good on any size of screen.

Create your own PLF

The principal branded PLF systems use their own customised, or specified digital projectors, with usually a pair needed to help fill the largest screens, together with the obligatory immersive sound. However, there’s nothing to prevent any cinema from creating its own bigger screen auditorium, using its own choice of technology and thinking up a good name for it — IHS Markit recently established that there are currently 72 brands worldwide. Names already promising a premium viewing experience in the UK and beyond include: Impact, Isense and Finity which, like those from the past with ‘70’ in the title, mean that cinemagoers are again in for something special — which can only be good!