What Makes IMAX Different

INTRODUCTION

There are two parts to getting a movie into a cinema.

First, the film needs to be captured with a camera.

And second, it needs to be presented by projecting that image onto a screen.

Imax basically took both of these parts from traditional cinema and supersized them, creating a camera system that captured enormous, top quality, high resolution images, and combined that with a projector that cast the film onto a gigantic sized screen.

So let's dive a bit further into the details of this technical process by looking at what makes Imax cameras different from regular cinema cameras, how it affects the footage and why this high quality format is only used on a small handful of movies. 

IMAX CAMERAS

To understand Imax and what makes this format different, we need to first know how most mainstream movies are captured. Up until about a decade ago, almost all movies were shot and presented using 35mm film. These have since been replaced by digital cameras, but we’ll get to that a bit later. 

35mm film is a photochemical emulsion that, as the name suggests, has a total width of 35mm, which records by passing it vertically through the camera. However, as some of that frame width needs to be used to accommodate sprocket holes, which are called perfs, that pass the film through the camera - the total usable size of a 35mm frame is around 24.90mm.

Different methods can be used to record 35mm frames at different heights, which I went over in another video, however the tallest possible 35mm film size that can be shot is 18.70mm.

If we compare this to the Imax frame, with its approximate size of 70x48mm we can see that it’s over eight times the size of what traditional cinema cameras capture.

The larger the surface area of a piece of film, the more photographic information it will contain. This means that an Imax image resolves much more detail and has very little visible film grain. Basically, Imax footage will look significantly cleaner and higher quality.

But, how do these cameras record such a big frame?

Instead of using 35mm film, they use a larger gauge 65mm stock. Again, once the extra space for the perfs on the side has been removed, it leaves us with a frame width of around 48.5mm.

If you compare 35mm and 65mm frames on film, you may also notice that the perfs for the 65mm sprockets are on the top and bottom rather than on the left and right. This is because 65mm Imax film runs horizontally through a camera, rather than 35mm which runs vertically. 

Passing through the gate horizontally gives Imax the advantage of being able to record a frame width that is larger than its 48mm size - which now becomes the frame height.

Each frame that Imax cameras record is 15 of these little perforations long, which is why this format is sometimes referred to as 15/70.

IMAX CAMERA GEAR

There are only 26 of these incredibly niche Imax cameras in the world. As such it’s a bit tricky to find information about these cameras but one of the most popular Imax film cameras is the MSM 9802, which is a sort of general purpose camera with a magazine that can hold 1,000ft of film.

Then there are also the Imax MKIV, MKIII and MKII bodies, which includes a “lightweight” version that holds 500ft of film.

Because the size of the film is so large, Imax have designed special lenses that have enough coverage to be used with these cameras without vignetting. They are made from glass by Carl Zeiss which are rehoused and designed specially for Imax.

Other third party lenses, such as rehoused Hasselblad medium format lenses from Panavision or their large format Sphero and System 65 lenses can also be used to cover the Imax format.   

DIGITAL IMAX CAMERAS

Since the early 2010s digital cinema cameras have largely overtaken using physical film to shoot movies.

However, because of its enormous negative size, many have argued that there is still no digital equivalent that can match up to the extremely high resolution, photographic feel and colour that Imax film delivers - which is estimated to be the digital equivalent of around 18,000 pixels.

DIGITAL IMAX CAMERA GEAR

Having said that, Imax has moved with the times and approved a list of high end digital cinema cameras, which they consider to be ‘Imax certified’. These include the 6.5K Arri Alexa 65 Imax, the Alexa LF and Mini LF, the Sony Venice, 8K Raptor and Monstro from Red and the Panavision DXL2 - with its rehoused Red sensor.

PROJECTION

Just like the Imax camera, that captured footage by moving the film horizontally, so did the first Imax projector need to be reconfigured and designed so that the film could pass horizontally past a gate, pause for a tiny fraction of a second as the light from the projector bulb illuminated the image on the massive Imax screen, before moving to the next piece of film.

The area that they projected onto was also much larger than traditional cinema screens - with the average screen size being around 18x24m.

ASPECT RATIOS

15-perf Imax is shot and presented in its tall, native aspect ratio of 1.43:1. This squarer format is a great ratio for using more symmetrical, central compositions, for framing singular characters, and incorporating more lateral height into the shot.

While the film industry was transitioning to shooting on digital cinema cameras, so too were cinemas changing from film to digital projection. In 2008 Imax introduced their first 2K Xenon digital projector - which they used to extend the number of Imax screens by expanding to regular cinemas - not only the custom built, enormous Imax screens.

Digital projection changed Imax in two important ways: firstly it changed the aspect ratio for 2K digitally projected Imax movies to a wider 1.90 frame - that chopped off the top and the bottom of the original Imax frame. Secondly it greatly reduced the resolution of the projection from the estimated 12K to 18K pixels in the Imax film negative to a 2K file.

In 2014 a 4K digital Imax projector was also introduced. This higher resolution projector used lasers as a light source to project an image twice as bright with a better contrast ratio than the 2K projectors. 

The increased power of this projector allowed it to show both the 1.43:1 full Imax negative on larger screens, or the wider 1.90 frame on smaller screens.

This means that some movies can now be distributed to both 2K Imax venues in 1.90:1 and some Imax film projectors in 1.43:1. 

Filmmakers need to keep all of these formats in mind when lining up their shots, to find a frame that works well in a wide aspect ratio as well as a tall one. Usually this means that the original Imax negative will include a lot of headroom for characters, which can then get cropped for the wider format.  

VISUAL CHARACTERISTICS

So, what is it that makes movies shot on Imax feel different from regular 35mm film or the equivalent Super 35 digital cinema cameras? Other than highly resolved detail and clean shots with minimal specs of film grain or noise.

Because the size of the negative that you are shooting on is so large, it produces a different field of view. In other words if you use the same lens on a Super 35 camera and an Imax camera, the Imax footage will look a lot wider, while the Super 35 footage will look more ‘cropped in’.

Cinematographers will often compensate for this extra width by using longer focal length lenses. So, where they would normally use something like a 21mm lens on a Super 35 camera to get a wide field of view, they’d have to go to a 50mm lens on Imax to get a similar wide perspective.

Using longer focal length lenses means that the depth of field will be shallower. 

So, practically, this means that Imax cameras can film wide shots on longer lenses, and achieve a shallow depth of field - where the background is out of focus. 

Whereas Super 35 cameras would use wider lenses to shoot a similar perspective which renders much more of the shot sharply in focus.

DRAWBACKS

Imax does come with some notable downsides. The first and most obvious drawback is cost. Imax cameras are incredibly niche which makes them a bit expensive to rent. But, more importantly, the price of buying and processing the amount of 65mm film required to shoot on Imax is incredibly high. 

This is because 15 perforations per frame moving through the gate 24 times in 1 second, works out to around 337ft of 65mm film for every minute that is shot.

If we do a super rough calculation: 400ft of 65mm film costs $619, developing and scanning one minute of film can cost somewhere around $490, so you’re probably looking at paying somewhere close to $1,000 for each minute of film that is shot. Of course they'll be bulk discounts and whatnot for features but, point is it’s not going to be cheap.

Another negative is that because the 15 perfs of film need to run through the camera so much quicker than regular 4 perf 35mm, Imax cameras are incredibly noisy when shooting. This makes it difficult if not impossible to record clean sync sound audio without hearing the whir of the film running.

Finally, they are incredibly bulky, heavy and cumbersome to operate. They were designed to be operated from tripods or on a remote head on a helicopter - certainly not handheld.

These limitations meant that Imax was only used for many years to shoot exhibition sorts of films, like short documentaries with aerial footage and wides of landscapes.

Imax footage was later incorporated into feature films in key action sequences, while the majority of the film’s dialogue sequences were filmed using more traditional 35mm camera systems.

However in recent years, filmmakers like Chritopher Nolan who have access to large budgets have pushed hard for the format to be used to shoot entire narrative feature films. This has involved finding solutions to some of the technical challenges posed by these bulky, noisy, expensive machines.

Recent news has also come to light that Imax will release a new, redesigned version of the Imax camera, based on feedback from filmmakers, in 2024. 

This may make the format even more usable and easy to work with as a feature film making tool. So, it seems that as long as cinema releases remain a thing and as long as there are directors and audiences that appreciate this super high quality format then Imax should still be around for quite some time.