Infrared in cinema: the new golden age

In 2024, at least four films including scenes filmed with infrared (IR) were released in cinemas: The Area of ​​Interest, Dune 2, Planet B et Aggro Drift. The latter is even the first fiction feature film entirely shot in IR. These films, ranging from experimental to blockbuster, make 2024 a high point in the little-known history of IR in cinema.

Infrared is a long-time companion of cinema, often unnoticed by film viewers. For nearly 90 years, this light has sometimes been used for various image manipulation processes (including American night, the strangeness effect, contrast accentuation) or to document its military use.

In the same way as visible light or X-rays, infrared corresponds to a delimited set of electromagnetic radiation, characterized by a wavelength between 0.7 and 1,000 μm. Infrared radiation is invisible to us because our eye does not perceive wavelengths greater than 0.7 µm, corresponding to red. The infrared spectrum is subdivided into five wavelength ranges, all of which have their own applications.

The two domains used in cinema are NIR and LWIR. NIR, for “near infrared” in English, brings together the smallest wavelengths, from 0.7 to 2.5 µm. LWIR, for “long wave infrared” in English, extends from 7 to 14 µm.

A first golden age exploiting the NIR

The discovery of infrared is attributed to William Herschel in 1800. His son John produced the first infrared image 40 years later. In 1925, Kodak marketed the first so-called “infrared” film: it was sensitive to visible radiation and also to NIR radiation. Several other brands marketed them in the following years, specializing in different combinations of wavelengths (such as UV, blue, and NIR): up to 33 different infrared films were available in 1937. This paved the way to the first infrared “golden age” of cinema, which spanned mainly the years surrounding the Second World War.

At a time when films were shot exclusively in black and white, a chromatic particularity of the images obtained in the NIR proved to be interesting: the sky observed in the NIR appeared black, which was ideal for simulating nighttime by shooting during the day ( filming process called “American night” in France). The technique is, however, complicated to use and requires a lot of adjustments to avoid obtaining an image with strange contrast. It often requires painting specific surfaces of the set, adapting the color of the costumes or even applying special makeup to the actors’ faces. Most of the films shot with IR during this period will be to produce American nights, but not only.

This first golden age will end with the decline of black and white, around 1960. A film can be presented as its swan song: I am Cuba (1964), by Mikhail Kalatozov. This film is of extreme formal ambition: it is made up of sequence shots of insane sophistication for the technical means of the time, and uses infrared, which accentuates the contrast of the black and white image and reinforces the chromatic beauty of certain sequences. To do this, the filmmaker and his cinematographer had to divert a stock of film from the Soviet army.

Predator and the beginnings of the exploitation of the LWIR

At the same time, infrared video imaging technology is booming, thanks to its military applications – infrared imaging is used by the army to see at night, through fog or camouflage. The first so-called “thermal” cameras were marketed in 1965. Such cameras image in the LWIR spectral domain, also called “thermal infrared”. All objects emit electromagnetic radiation whose wavelength and intensity depend on their temperature. This explains the phenomenon of incandescence: a metal turns red then whitens when it is heated to white. Objects at room temperature are too cold to emit light visible to the human eye – the light they emit is actually infrared in the LWIR range. Since the energy of light is inversely proportional to its wavelength, LWIR radiation is much less energetic than NIR, requiring a very different and more sophisticated detection technology.

Until the development of thermal cameras, LWIR radiation was therefore technically inaccessible to film cameras, and therefore to cinema. But from 1965, it would take another 20 years for the history of infrared and cinema to intersect again, in fact until 1987 with the release of Predatorby John McTiernan.

This film narrates the hunt by an extra-terrestrial creature of a squad of soldiers in the middle of the jungle. The most striking feature of the Predator is that it sees in a range of wavelengths corresponding to LWIR. This translates on screen into numerous scenes imitating a first-person view during which the viewer “sees in infrared”.

They were filmed with the help of a FLIR military camera, which represented a technical feat at the time. The difference in resolution of the video signal from the thermal camera compared to 35 mm film is so abysmal that a device was invented to optically combine the IR thermal image with the visible one. Another limitation: the thermal camera was no longer able to distinguish the heat of a human body from the rest of the scene as soon as the temperature exceeded 34°C. When filming in the middle of a tropical jungle, the production sometimes had to cool the forest by spraying ice water!

Using thermal IR for a film in 1987 was therefore a real technical tour de force. Two examples still allow us to measure this. In Aliens, the returnreleased shortly before Predatorthe marines responsible for eliminating aliens are equipped with infrared glasses. In one scene, they try to spot them by their heat signature – but no image of their IR vision will ever be shown on screen. Then in Robocopthis time released shortly after Predatorthermal IR vision is indeed shown on screen, but it was obtained without using an LWIR camera: the sequence was in fact shot at night by a conventional camera with actors covered in fluorescent paint. The visual rendering, with the retrospective vision of a viewer today, is not at all convincing!

Predatorthrough its pioneering status, is certainly the most important fiction film for the democratization of infrared imaging among the general public. The film has already had four sequels. But from an artistic point of view, its use of IR remains limited to a simple transposition of the military use of IR technology into a fictional SF framework.

A second golden age enabled by the digitalization of cinema

From 2000 to 2010, cinema shifted to digital, with the indirect consequence of the advent of a second golden age of IR. The CCD sensors of digital cameras are in fact naturally sensitive in the NIR – an optical filter is in fact installed to cut these wavelengths… which simply needs to be removed or changed to film in the NIR. Digital technology also greatly facilitates the use of images obtained by LWIR video cameras in film editing. Modern uses of IR in cinema can be classified into three categories.

First, IR is used for the same reasons as in the First Golden Age. It was used to produce American nights in Nopeor to simulate the lighting conditions prevailing on an extra-terrestrial planet (the Moon in Ad astra and Giedi Prime in Dune 2) – as had already been done in 1937 in the serial Flash Gordon’s trip to Mars.

The second category of use includes films featuring armed forces: infrared sights are now part of the military equipment, it is natural to find IR images in works featuring them (Neither heaven nor earth).

Finally, the new artistic uses of IR constitute the last category: representing an altered state of consciousness: intoxication (Cherry), near-death experience (Alexandre), show the goodness of a little girl in the hell of the camps (The Area of ​​Interest), give a psychedelic-cyberpunk look to a gangster film (Aggro Drift).

The technological developments which enabled the conquest of the moon in the 1960s were nourished (and vice versa) by artistic representations of this conquest, particularly cinematographic ones.

In the same way, will cinema inspire future uses of infrared? One of the motivations for using LWIR to Aggro Drift is that the resulting images were easier to modify by artificial intelligence – the film is full of digital pattern overlays on the characters’ skin or in the sky. IR camera manufacturers are working on integrating AI into their products…