How Infrared Photography Works in General
To understand how infrared photography works, we need to understand that infrared photography uses films or other optical means sensitive to infrared light, i.e. infrared radiation. All radiation can be characterized as a wavelength; in this sense, light is no exception.
What is considered “light” is visible light, the part of electromagnetic radiation that we can see with our sense of sight, including our eye and the part of the brain responsible for vision. In doing so, we see different colors, from purple, blue, green, yellow, orange to red and extremely red. Technically speaking, infrared light is radiation rather than light, however, the term “infrared light” is generally accepted, especially when talking about infrared photography.
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- History of Infrared Photography
- Classic Infrared Photography
- Applications of Infrared Photography
History of Infrared Photography
The first infrared photograph was published in February 1910 in The Century Magazine. Later in October of the same year, Robert. W. Wood publishes infrared photographs of landscapes in the Royal Photographic Society Journal using experimental film, adding colorants to silver halides, i.e. photosensitive emulsion. In this way, he was able to record infrared light and create unusual effects, so even today infrared photos are often called photos with the Wood effect.
In 1930, Kodak began producing infrared films used in astronomy. In the period 1930 – 1937, infrared photography became available to photography enthusiasts after first Ilford, and then Agfa and Kodak started producing infrared films, even for the needs of shooting feature films.
The false color infrared film launched in 1942 by Kodak under the name Ektachrome Infrared Aero Film and Ektachrome Infrared becomes a widely used film and was available in 35mm format for infrared photography. Infrared photography became especially used in the 60s of the 20th century to create album covers of then popular musicians due to its specific effects, unexpected colors and psychedelic aesthetics, promoted in the late 60s by Jimi Hendrix, Donovan, Frank Zappa and the Grateful Dead.
Many photographers such as Elio Ciolo and Martin Reeves used subtle black and white films sensitive to infrared light. With the development of digital infrared photography, this technique became very popular and appreciated, and such photographic works were often sold in art galleries around the world.
Classic Infrared Photography
Taking classic infrared photos was made possible by the production of adequate films for infrared photography, whether it is black-white infrared photography or infrared color photography. However, infrared photography film is extremely sensitive to visible light wavelengths.
Therefore, for taking classic infrared photos, special equipment is needed in the form of a filter that is placed in front of the lens of the camera, which blocks visible light and allows the passage of longer wavelengths of the infrared spectrum.
Black and White Infrared Photography
Black and white films for infrared photography are sensitive to shorter wavelengths of infrared light in the range of 700 to 900 nm and most are also sensitive to wavelengths of blue light.
The peculiar haze or glare effect often seen on the illuminated parts of infrared photographs is an effect resulting from long-term use of Kodak’s High-Speed Infrared (HIE) film and is not due to the infrared light itself, but is caused by the lack of a suitable layer on the back of Kodak’s HIE film.
Most black-and-white infrared photographs of artwork, landscapes, or wedding photography are made using orange, red, or opaque filters over the lens to block visible blue light during exposure. So, the purpose of the filter in black and white infrared photography is to prevent the passage of blue light wavelengths and allow the passage of infrared light.
Without a filter, infrared film negatives look a lot like classic film negatives because the blue light reduces the contrast and significantly prevents the infrared appearance of the film.
Some photographers use an orange or red filter to allow a slight entry of blue light wavelengths and thus enrich the film, which again reduces contrast. Intensely dark-red filters block almost all blue light, while opaque filters block not only blue light but also red light wavelengths. This results in a clean infrared photo with stronger contrast.
The aforementioned Kodak HIE film is sensitive to wavelengths over 900 nm and to the entry of visible light, so inserting and removing the film as well as its processing had to be done in complete darkness. The film itself, made of a polyester base, was very susceptible to scratches and required special care during handling in the process of developing and making photographs to avoid its damage. Due to the decrease in demand for this product, Kodak stopped producing it in November 2007.
Color Infrared Photography
Infrared color photography uses transparent color films that have three layers that, because of the way the colors are combined, reproduce infrared light as red, red as green, and green as blue light, shifting the wavelength toward smaller ones.
All these layers of the film are sensitive to the wavelengths of blue light, so a yellow filter must be used, since it blocks blue light but allows other colors to be obtained to obtain an interesting and color-rich photo.
Generally speaking, infrared color films are less sensitive to light than black and white films, and it is not necessary to insert them in complete darkness. The most widely used infrared color film was Kodak’s Ektachrome Professional Infrared/EIR, however Kodak announced in 2007 that it was discontinuing the production of the 35 mm version of this film due to reduced demand and continued to produce the 70 mm Aerographic format.
Many photographers think that with today’s digital cameras it is not possible to achieve the same results as with Kodak film for infrared color photography, although similar effects can be produced by using double exposures, one for infrared and one for full-color photography, with the application of post-processing of the film.
Infrared color photography, as part of the overall photographic spectrum, is becoming more and more popular. The ease of creating and taking photos of delicate colors with the integrated characteristics of infrared photography makes this type of photography more and more popular and interesting for both recreational photographers and professionals.
Applications of Infrared Photography
The application of infrared photography is multifaceted, and this is made possible by its main characteristic – the ability to display an image that is otherwise invisible to the human eye. Infrared photography records radiation and electromagnetic waves in the range beyond the visible spectrum, which is why the effects of infrared photos are sometimes surprising and very interesting.
However, infrared recorded material has not only an artistic nature, but is also used for very practical purposes starting from medicine, astronomy, criminology, and for military, meteorological, geological and other purposes.
Infrared Photography in Medicine
In medicine, the application of infrared photography has found its full justification, because using infrared radiation it reaches inside the human body, revealing medical problems at an early stage, for which timely diagnosis is often the key to successful healing and disease remission, for example in the case of tumors. In addition to the above, infrared radiation and infrared photography are based on their help in diagnosing diseases of the peripheral circulation and the circulatory system in general, as well as nerve damage.
Its role in dental medicine is also not negligible when detecting damage to the tooth enamel, which appears on the infrared image as darkening compared to the rest of the healthy part of the tooth.
Infrared Photography for Military Purposes
Infrared photography is used for military purposes primarily to detect desired targets, which cannot be detected by conventional imaging methods. If aerial photography is used, different brightness intensities will be observed in the photographs depending on the amount of radiation of the individual object.
Night vision devices are used when there is not enough light for normal vision. These devices work by converting light photons into electrons, which are then amplified, either chemically or electrically, and then converted back into visible photons. In this sense, night vision devices can be part of military equipment but also serve other peacetime practical purposes.
Infrared Photography in Criminology
In the field of criminology, infrared photography is essential when securing evidence, both at the crime scene and in subsequent laboratory examinations. In particular, infrared photography proved useful after the introduction of digital cameras, which ensure a sufficient number of photos for processing evidence, and also reduce the time of production and availability of finished photos as evidence, which is a big advantage compared to analog recordings.
Infrared photography can be used to document evidence related to prints and remains of gunpowder and other fire parts weapons, remains of tissue or blood, searching for remnants of clothing or recording injuries to either the victim or the suspect, both on the surface of the skin and under it. Also, for criminal purposes, infrared photography is used to detect fugitives in a wider area in the same way that it was explained when using this type of photography for military purposes.
The special importance of infrared photography is in the case of counterfeits of any form, where changes in the pigmentation of counterfeit parts of the object can easily be seen in the images.
Infrared Photography in Astronomy
Now we will give you a more detailed explanation of how infrared photography works for astronomy.
Infrared photography is widely used in astronomy and deals with the study of electromagnetic radiation emitted by all objects in space. This type of photography in space makes it possible to observe objects that are hidden behind clouds of gases, space dust and nebula that obscures the view in the visible part of the spectrum. Infrared photography captures galaxies, the birth and death of stars, interstellar molecules and electromagnetic wave currents, but also the center of our galaxy and planet.
Infrared photography is used to obtain data that will help determine the age of the parent galaxy, the age of the universe and its origin, and the phenomenon of its expansion.
Astronomers observe space objects in the infrared region of the electromagnetic spectrum, with all the parts for optical telescopes, including mirrors, lenses and detectors. To obtain images in the infrared spectrum, parts of the optical equipment must be carefully shielded, and the detectors are usually cooled with liquid helium.
The sensitivity of infrared telescopes on Earth is significantly limited due to water vapor in the atmosphere, which absorbs part of the infrared spectrum, which comes from space, except in the areas of “atmospheric windows”. For this reason, it is better to place infrared telescopes at high altitudes, place them in hot air balloons or airplanes.
Infrared telescopes are useful for astronomers because cold and dark molecular clouds of gas and dust obscure the view of many stars. Infrared telescopes are also used to observe protostars before they start emitting visible light.
Since stars emit very little in the infrared region, it is possible to detect reflected light from planets. The first infrared satellite launched into Earth’s orbit was called IRAS (Infrared Astronomical Satellite). Considering that the Earth’s atmosphere absorbs part of the electromagnetic radiation and does not pass it to the Earth’s surface, it’s positioning in orbit provides more precise data based on infrared photographs that improve human knowledge of the universe.
Infrared Photography in Geology
Infrared photography in geology is used to record and observe geological-morphological aspects that cannot be seen with the naked eye, color photography or conventional black-and-white photography. Using satellite or airplane imaging, areas of environmental, water or air pollution are determined because it emits different infrared radiation than normal.
Healthy vegetation appears white in photographs, while burnt or destroyed vegetation appears dark in infrared photographs. Photos taken near water attract certain vegetation and give a different infrared image than areas with less water. Taking infrared photos from satellites is significant in that mineral sources can be found, but also ground and tectonic plate movements can be measured. Infrared photography can also be used to measure the composition of the Earth’s crust.
Infrared Photography in Meteorology and Climatology
Meteorological satellites, equipped with radiometers, create thermal as well as infrared images, on which meteorologists can determine the type and height of clouds, the temperature of water surfaces and land, and thus make very precise and long-term accurate weather forecasts and climatological predictions.
Infrared Photography in Art History
Infrared reflectograms, as they are called by art historians, are used to reveal hidden layers of color in art paintings. This serves them to find out if the image is an original or a copy, or if the image has been altered with restoration work. Infrared devices are also useful in discovering old writings, such as the “Scrolls from the Dead Sea” or writings found in Mogao Cave.
What is infrared photography?
How infrared photography works?
Here is a quick answer on how infrared photography works. Infrared photography works by capturing light in the infrared spectrum, which is beyond the range of visible light. To do this, a special filter is used on the camera lens that blocks visible light and allows only infrared light to pass through. The camera then captures the infrared light and converts it into a visible image.
What types of cameras can be used for infrared photography?
Any camera that is capable of using interchangeable lenses can be used for infrared photography. However, cameras that have been modified, specifically for how infrared photography works, can produce better results. These modifications involve removing the camera’s infrared-blocking filter and replacing it with a filter that allows infrared light to pass through.
What are the benefits of infrared photography?
Infrared photography can produce unique and often surreal images that cannot be captured with visible light photography. It can also reveal details and textures that are not visible to the human eye, making it a useful tool for scientific and technical applications.
What are some challenges with infrared photography?
Infrared photography can be challenging because the infrared light that is captured can sometimes cause color shifts and other distortions in the final image. It can also be difficult to find the right balance between capturing enough infrared light and not overexposing the image. Additionally, infrared filters can reduce the amount of light that reaches the camera sensor, which can make it difficult to capture sharp images in low-light conditions.