Infrared photography
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In infrared photography, the
to about 900 nm. Film is usually sensitive to visible light too, so an infrared-passing filter is used; this lets infrared (IR) light pass through to the camera, but blocks all or most of the visible light spectrum (the filter thus looks black or deep red). ("Infrared filter" may refer either to this type of filter or to one that blocks infrared but passes other wavelengths.)When these
The other attributes of infrared photographs include very dark skies and penetration of atmospheric haze, caused by reduced Rayleigh scattering and Mie scattering, respectively, compared to visible light. The dark skies, in turn, result in less infrared light in shadows and dark reflections of those skies from water, and clouds will stand out strongly. These wavelengths also penetrate a few millimeters into skin and give a milky look to portraits, although eyes often look black.
History
Until the early 20th century, infrared photography was not possible because silver halide emulsions are not sensitive to longer wavelengths than that of blue light (and to a lesser extent, green light) without the addition of a dye to act as a color sensitizer.[2] The first infrared photographs (as distinct from spectrographs) to be published appeared in the February 1910 edition of The Century Magazine and in the October 1910 edition of the Royal Photographic Society Journal to illustrate papers by Robert W. Wood, who discovered the unusual effects that now bear his name.[3][4][5] The RPS co-ordinated events to celebrate the centenary of this event in 2010.[6] Wood's photographs were taken on experimental film that required very long exposures; thus, most of his work focused on landscapes. A further set of infrared landscapes taken by Wood in Italy in 1911 used plates provided for him by C. E. K. Mees at Wratten & Wainwright. Mees also took a few infrared photographs in Portugal in 1910, which are now in the Kodak archives.
Infrared-sensitive photographic plates were developed in the United States during World War I for spectroscopic analysis, and infrared sensitizing dyes were investigated for improved haze penetration in aerial photography.[7] After 1930, new emulsions from Kodak and other manufacturers became useful to infrared astronomy.[8]
Infrared photography became popular with photography enthusiasts in the 1930s when suitable film was introduced commercially. The Times regularly published landscape and aerial photographs taken by their staff photographers using
Infrared movie film was also available and was used to createFalse-color infrared photography became widely practiced with the introduction of Kodak Ektachrome Infrared Aero Film and Ektachrome Infrared EIR. The first version of this, known as Kodacolor Aero-Reversal-Film, was developed by Clark and others at the Kodak for camouflage detection in the 1940s. The EIR film became more widely available in 35mm form in the 1960s but has been since discontinued.
Infrared photography became popular with a number of 1960s recording artists, because of the unusual results; Jimi Hendrix, Donovan, Frank Zappa and the Grateful Dead all issued albums with infrared cover photos. The unexpected colors and effects that infrared film can produce fit well with the psychedelic aesthetic that emerged in the late 1960s.[citation needed]
Infrared light lies between the visible and microwave portions of the electromagnetic spectrum. Infrared light has a range of wavelengths, just like visible light has wavelengths that range from red light to violet. "Near infrared" light is closest in wavelength to visible light and "far infrared" is closer to the microwave region of the electromagnetic spectrum. The longer, far infrared wavelengths are about the size of a pin head and the shorter, near infrared ones are the size of cells, or are microscopic.
Focusing infrared
Most
Most
Zoom lenses may scatter more light through their more complicated optical systems than prime lenses, that is, lenses of fixed focal length; for example, an infrared photo taken with a 50 mm prime lens may have more contrast than the same image taken at 50 mm with a 28–80 zoom.
Some lens manufacturers such as Leica never put IR index marks on their lenses. The reason for this is that any index mark is only valid for one particular IR filter and film combination, and may lead to user error. Even when using lenses with index marks, focus testing is advisable as there may be a large difference between the index mark and the subject plane.
Film cameras
Many conventional cameras can be used for infrared photography, where infrared is taken to mean light of a wavelength only slightly longer than that of visible light. Photography of rather longer wavelengths is normally termed thermography and requires special equipment.
With some patience and ingenuity, most film cameras can be used. However, some cameras of the 1990s that used 35mm film have infrared sprocket-hole sensors that can fog infrared film (their manuals may warn against the use of infrared film for this reason). Other film cameras are not completely opaque to infrared light.
Black-and-white infrared film
Black-and-white infrared negative films are sensitive to wavelengths in the 700 to 900 nm
The majority of black-and-white infrared art, landscape, and wedding photography is done using orange (15 or 21), red (23, 25, or 29) or visually opaque (72) filters over the lens to block the blue visible light from the exposure. The intent of filters in black-and-white infrared photography is to block blue wavelengths and allow infrared to pass through. Without filters, infrared negative films look much like conventional negative films because the blue sensitivity lowers the contrast and effectively counteracts the infrared look of the film. Some photographers use orange or red filters to allow slight amounts of blue wavelengths to reach the film, and thus lower the contrast. Very dark-red (29) filters block out almost all blue, and visually opaque (70, 89b, 87c, 72) filters block out all blue and also visible red wavelengths, resulting in a more pure-infrared photo with a more pronounced contrast.
Certain infrared-sensitive films like Kodak HIE must only be loaded and unloaded in total darkness.[11] Infrared black-and-white films require special development times but development is usually achieved with standard black-and-white film developers and chemicals (like D-76). Kodak HIE film has a polyester film base that is very stable but extremely easy to scratch, therefore special care must be used in the handling of Kodak HIE throughout the development and printing/scanning process to avoid damage to the film. The Kodak HIE film was sensitive to 900 nm.
As of November 2, 2007, "KODAK is preannouncing the discontinuance" of HIE Infrared 35 mm film stating the reasons that, "Demand for these products has been declining significantly in recent years, and it is no longer practical to continue to manufacture given the low volume, the age of the product formulations and the complexity of the processes involved."[12][13] At the time of this notice, HIE Infrared 135-36 was available at a street price of around $12.00 a roll at US mail order outlets.
Arguably the greatest obstacle to infrared film photography has been the increasing difficulty of obtaining infrared-sensitive film. As of 20 October 2020[update], the discontinuance of Kodak HIE and Efke's IR820 has now narrowed the selection for black and white infrared film to the Rollei Infrared 400 film, which has become the only IR film on the market with good sensitivity beyond 750 nm; the Rollei film does extend beyond 750 nm but IR sensitivity falls off very rapidly.
Color infrared film
Color infrared transparency films are based on an emulsion which, similar to standard color film, contains at least three separate photosensitive layers. Each layer is specifically sensitized to produce a desired color. Grains of light-exposed silver halide in these layers react with a reducing agent to form metallic silver particles. This produces oxidized developer, which reacts with compounds called color couplers in the emulsion layers to form various color dyes, respective to how the silver halide was originally sensitized for each layer.
Due to the fact that silver halides are sensitive to exposure outside of the visible range of the electromagnetic spectrum, at longer wavelengths, they can readily be used to produce dyes which correspond with infrared light. Without specialized intervention, silver halides are only sensitive to a wavelength shorter than around 450nm.[14]
Conventional color film is primed with a cyan forming layer, which gets exposed to light prior to the yellow and magenta forming layers stacked behind. Since these layers are also sensitive to blue light, often times, a yellow filter layer is placed in between the cyan forming layer, and the yellow and magenta forming layers. This serves to minimize undesired passthrough of wavelengths that are not supposed to expose the latter layers. The emulsion layer design for conventional color film is fairly direct: visible wavelengths correspond with respective layers designed to produce dyes which represent how we perceive these wavelengths as colors, using subtractive means. Color infrared film, in contrast, relies on translation. For example, long-wavelength infrared radiation forms yellow and magenta dyes to produce a red color, even though red dyes in this context do not describe something we can see in color. Further, red band radiation wavelengths form cyan and yellow dyes to produce a green color. Green band wavelengths form cyan and magenta dyes to produce a blue color.[15] Blue light is typically to be blocked out using a yellow filter. This is because the biased sensitivity towards short-wavelength radiation, characteristic of color infrared films, makes exposure to blue light undesirable, and unintended by design of the emulsion. Color infrared films have no intended blue-sensitized dye forming layer to expose, and thus, often no subsequent internal yellow filter layer built into the film. This requires photographers to use external minus-blue lens filters.
The health of foliage can be determined from the relative strengths of green and infrared light reflected; this shows in color infrared as a shift from red (healthy) towards magenta (unhealthy). Early color infrared films were developed in the older E-4 process, but Kodak later manufactured a color transparency film that could be developed in standard E-6 chemistry, although more accurate results were obtained by developing using the AR-5 process. In general, color infrared does not need to be refocused to the infrared index mark on the lens.
In 2007 Kodak announced that production of the 35 mm version of their color infrared film (Ektachrome Professional Infrared/EIR) would cease as there was insufficient demand. Since 2011, all formats of color infrared film have been discontinued. Specifically, Aerochrome 1443 and SO-734.
There is no currently available digital camera that will directly produce the same results as Kodak color infrared film although equivalent images can be produced using a full spectrum infrared digital camera and a Kolari Vision Color IR Chrome lens filter. [16] Similar effects can be achieved by taking two exposures, one infrared and the other full-color, and combining in post-production. A yellow (minus-blue) filter can also be used, which provides a single image that can also be post-processed to emulate the Ektachrome look.[17] The color images produced by digital still cameras using infrared-pass filters are not equivalent to those produced on color infrared film. The colors result from varying amounts of infrared passing through the color filters on the photo sites, further amended by the Bayer filtering. While this makes such images unsuitable for the kind of applications for which the film was used, such as remote sensing of plant health, the resulting color tonality has proved popular artistically.
Color digital infrared, as part of
Availability
In 2008, Los Angeles photographer, Dean Bennici started cutting and hand rolling Aerochrome color Infrared film. All Aerochrome medium and large format which exists today came directly from his lab. The trend in infrared photography continues to gain momentum with the success of photographer Richard Mosse and multiple users all around the world.[18]
Digital cameras
Since the Bayer filters in most digital cameras absorb a significant fraction of the infrared light, these cameras are sometimes not very sensitive as infrared cameras and can sometimes produce false colors in the images. An alternative approach is to use a Foveon X3 sensor, which does not have absorptive filters on it; the Sigma SD10 DSLR has a removable IR blocking filter and dust protector, which can be simply omitted or replaced by a deep red or complete visible light blocking filter. The Sigma SD14 has an IR/UV blocking filter that can be removed/installed without tools. The result is a very sensitive digital IR camera.
While it is common to use a filter that blocks almost all visible light, the wavelength sensitivity of a digital camera without internal infrared blocking is such that a variety of artistic results can be obtained with more conventional filtration. For example, a very dark neutral density filter can be used (such as the Hoya ND400) which passes a very small amount of visible light compared to the near-infrared it allows through. Wider filtration permits an SLR viewfinder to be used and also passes more varied color information to the sensor without necessarily reducing the Wood effect. Wider filtration is however likely to reduce other infrared artefacts such as haze penetration and darkened skies. This technique mirrors the methods used by infrared film photographers where black-and-white infrared film was often used with a deep red filter rather than a visually opaque one.
Another common technique with near-infrared filters is to swap blue and red channels in software (e.g. Adobe Photoshop) which retains much of the characteristic 'white foliage' while rendering skies a glorious blue.
Several Sony cameras had the so-called Night Shot facility, which physically moves the blocking filter away from the light path, which makes the cameras very sensitive to infrared light. Soon after its development, this facility was 'restricted' by Sony to make it difficult for people to take photos that saw through clothing.[20] To do this the iris is opened fully and exposure duration is limited to long times of more than 1/30 second or so. It is possible to shoot infrared but neutral density filters must be used to reduce the camera's sensitivity and the long exposure times mean that care must be taken to avoid camera-shake artifacts.
Phase One digital camera backs can be ordered in an infrared modified form.
See also
Notes
- ^ The Wood Effect results from the transparency of chlorophyll at wavelengths over 500 nm allowing light to be reflected within the plant cells. Normally the effect is invisible because so much green light is reflected by the foliage but it is possible to see the effect, albeit dimly, with the naked eye by looking through a 720 nm filter (or similar) on a sunny day and allowing your eye to adjust to the low light.
- ^ "Chemistry of Photography". Retrieved 28 November 2006.
- ^ Robert W. Wood (February 1910). "A New Departure in Photography". The Century Magazine. 79 (4). The Century Company: 565–572.
- ^ Robert W. Wood (October 1910). "Photography By Invisible Rays". The Photographic Journal. 50 (10). Royal Photographic Society: 329–338.
- ^ "Pioneers of Invisible Radiation Photography – Professor Robert Williams Wood". Archived from the original on 12 November 2006. Retrieved 28 November 2006.
- ^ "100 Years of Infrared". The RPS Journal. 148 (10). Royal Photographic Society: 571. December 2008 – January 2009.
- ^ Annual Report of the Director Bureau of Standards to the Secretary of Commerce for the Fiscal Year Ended June 30, 1919 U. S. Govt. Print. Off., United States National Bureau of Standards, pp. 115–119, 1919.
- ^ Harvard paper, 1932 Early Infrared astronomy
- ^ Walter Clark (1939). Photography by infrared: its Principles and Applications. Wiley.
- ^ American Cinematographer 1941 Vol 22
- ^ This is because HIE lacks anti-halation layers and has a completely transparent base rather than being directly due to infrared sensitivity. Film usually has a slightly fogged base and anti-halation layers coated on it in order to stop light bouncing around in the substrate once the image has been taken. Light can enter film through the tail protruding from a 35mm canister and without a fogged base it will be piped into the film and expose it. Without an anti-halation layer any light entering the substrate through the emulsion will be reflected back and forth inside the film, becoming diffuse as it travels and causing halation. HIE lacked a fogged base and anti-halation layers for two reasons: sensitivity is increased by allowing light to reflect back and forth and it was difficult to find any way of treating the film that would be effective at infrared wavelengths.
- ^ Kodak, Discontinuance notice
- ^ "Due to declining demand, KODAK High-Speed Infrared Film / HIE has been discontinued, effective YE 2007."; Kodak, "Archived copy" (PDF). Archived from the original (PDF) on 9 May 2008. Retrieved 31 October 2016.
{{cite web}}
: CS1 maint: archived copy as title (link) - ISBN 978-3-642-05902-5.
- LCCN 77-90786.
- ^ "Kolari Vision IR Chrome Lens Filter". 6 February 2019.
- ^ "Emulating infrared Ektachrome".
- ^ "Jotta - Article". Archived from the original on 12 November 2014. Retrieved 12 November 2014.
- ^ "Photographic Techniques". www.armadale.org.uk. Retrieved 3 April 2018.
- ^ a b "Ultra-Personal Sony Handycam" (Press release). Reuters wire service. 12 August 1998. Retrieved 9 February 2007.
- ^ "Internal Cut Filter Transmission - Kolari Vision". kolarivision.com. 4 March 2015. Retrieved 3 April 2018.
- ^ "Digital Infrared at Jim Chen photography". www.jimchenphoto.com. Retrieved 3 April 2018.
- ^ "110mb.com - Want to start a website?". surrealcolor.110mb.com. Archived from the original on 15 February 2012. Retrieved 3 April 2018.
- ^ "IS-1 web page including EULA". fujifilmusa.com. Archived from the original on 22 July 2009. Retrieved 3 April 2018.
External links
- Media related to Infrared photography at Wikimedia Commons
- Simple Introduction to Digital Infrared Photography
- All you ever wanted to know about digital UV and IR photography, but could not afford to ask
- Gisle Hannemyr's Digital Infrared Resource Page will help you decide if your digital camera is IR-sensitive, and more
- Conversion instructions for the Canon G1
- List of cameras and their usefulness in digital infrared photography, and lenses that do and don't produce "ir hot-spots".
- Short video showing how to take infrared photographs
- Make your own budget IR camera
- Common problems with shooting digital infrared and how to avoid them