Digital Infrared Photography Manual

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Excellent collection of resources, tips and galleries for infrared photography.

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    Infrared (IR) basics for digital photographerscapturing the unseen

    Digital cameras make it easy to explore a world of invisible light just beyond red.

    In this topic...

    Why Infrared?o Extra-Sensory Perception

    o A Fresh View Within Easy Reach

    o The Digital Advantage

    o Sidebar: Jay Scott's Excellent IR Adventures

    o Near, Not Far IR

    o That IR Look

    IR Performance in Digital Cameras

    o Can Your Camera Handle IR?

    o What Makes a Good IR Camera?o Internal IR Cut Filters

    o Honey, Where's The Remote?

    o IR-Sensitive Cameras

    o Less Sensitive Cameras

    IR Filter Choices

    o First, Some Filter Terminology

    o NIR Transmission Spectra For Several Common IR Filters

    o The Ever-Popular Hoya R72

    o The Wratten 87 and 87co The Wratten 88a

    o What Do IR Filter Numbers Mean, Anyway?

    Basic IR Techniques

    o The Short Version

    o Apply Liberally

    o Know Your Sources

    o Sidebar: Black Body Radiation

    o Exposure And Camera Support

    o Supplemental Filterso Recording: Color vs. Grayscale

    o Focusing

    Whence the Digital IR Look?

    o Source Spectra

    o Relative NIR Reflectivities

    o Camera Variables

    o False Colors and Monochromes

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    o Sidebar: Forbidden Absorptions

    o R72 False Colors

    o Wratten 87 Grays

    o Wratten 87c Blues

    o White Balance Caught Blue-Handed

    o The Real Skinny?

    IR Contaminationthe Other Side of the IR Coin

    o If You Need Something To Worry About, Find Something Else

    o What Would IR Contamination Look Like?

    o Hot Mirror Filters A Cure Worse Than The Disease

    o The Heliopan 8125 "Digital" IR/UV-Cut Filter

    References and Links

    o IR Galleries

    o IR Information

    o

    Suppliers

    See also the IR/UV Checklist

    Last updated October 22, 2009

    Why Infrared?

    Conventional visible light photography is challenging enough. Why bother with infrared? Because it

    opens up an otherwise unseen corner of the world one of serene beauty and never-ending surprise.Digital cameras make this peek around the red end of the visible spectrum easier than ever before.

    On this page...

    Extra-Sensory Perception

    A Fresh View Within Easy Reach

    The Digital Advantage

    Sidebar: Jay Scott's Excellent IR Adventures

    Near, Not Far IR

    That IR Look

    Topic Index

    Last updated October 22, 2009

    Extra-Sensory Perception

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    Our senses strongly shape our understanding of theworld, as every photographer well knows, but theysample only small slices of the reality around us. Whatmight we learn and think and feel if we could hearbeyond 20-20,000 Hz, as our dogs do, or see beyondthe narrow visible light band at 400-700 nm?

    Curiosity about the world beyond natural perceptionmotivated some of our greatest inventions andscientific advances. Since the 17th century days ofGalileo and Leeuvenhoek, telescopes and microscopesworking with visible light have extended the reach ofhuman vision to ever larger and smaller scales today by many, many orders of magnitude. To say thatthese instruments have revolutionized all of scienceand much of Western philosophy and even religion inthe process would not overstate the case.

    In the last 2 centuries, visual observation escaped not only the human scale but also the visible spectrum that narrow band of electromagnetic (EM) radiation where the solar power spectrum and the sensitivityof the human eye both peak. (Certainly no coincidence there.) Cameras and films sensitive to infrared andultraviolet light gave us our first glimpses of a world awash in invisible light. Imaging devices based onmore exotic forms of light (X-rays, radio waves, etc.) soon followed and continue to proliferate.

    Today, as ever more sophisticated observing devices open up new segments of the EM spectrum to ourview and analysis, astronomers and cosmologists find it necessary to revise their understandings of thecosmos and even of our own solar system on an almost continuous basis. And along with theseviews of the world beyond the senses have come many scenes of unimaginable beauty. Any imageat Hubble Space Telescope Images by Subject or in the W. M. Keck Observatory gallery will attest to

    that.

    Out-of-spectrum experiences have generally been beyond the reach of theaverage photographer, but today's silicon-based consumer-grade digital camerasmake it easy to explore the strange and serene corner of the invisible worldfound just beyond visible red in the near infrared(NIR) band of the EMspectrum at 700-1200 nm (0.7-1.2) wavelengths. Throughout this article, theterms infrared,IR, near IR andNIR will refer to the 700-1200 nm band ofinterest to digital photographers unless otherwisenoted.

    To this day, the NIR remains one of the most usefulextra-visible bands in the EM spectrum. Aerialphotographers have long relied on NIR imagery tocapture the landscape with the greatestpossible clarity over a wide range of atmosphericconditions including some quite unsuitable forvisible light photography. For much the same reasons,

    Denver's Washington Park and the Rockies

    beyond

    Saturn's moon Titan at

    0.8-5.1 microns (near

    to far IR) as captured

    by Cassin on

    10/26/2004 from an

    altitude of ~450,000

    kilometers (280,000

    miles). Twin Keck telescopes

    atop Mauna Kea

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    the world-class Keck telescopes atop Mauna Kea (right) spend much of their precious observing time withsophisticated digital NIR detectors mounted. Abundant interstellar NIR radiation conveniently passesthrough dust, gas and our own atmosphere to allow glimpses into otherwise hopelessly obscured regionslike the Milky Way's galactic center.

    At left is one of humankind's first-ever looks at the surface of Titan, one of Jupiter's four large Gallileanmoons. The 0.8-5.1 micron infrared wavelengths were chosen specifically for the Cassini flyby in order to

    cut through the haze that completely obscured the surface to the Galileo flyby a decade earlier. Titan is inmany ways a frozen version of Earth.

    Page Index | Topic Index

    A Fresh View Within Easy Reach

    The world as seen in the NIR is at once familiar andstrange. The vastly different tonalities in the sunlit

    images at right show how widely the spectralproperties of common natural objects differ in theadjoining visible and NIR bands. Manmade objectsare full of surprises as well. (For some cheap fun,walk around the house with an IR filter mounted onyour digital camera and examine all your stuff throughthe LCD. You'll hardly recognize some of it.) We'llexplore some of the physical phenomena behind thesedifferences below.

    The false color schemes seen in digital IR images like the park scene at right and the leaf still-life

    at top are another matter entirely. The colors are nothing more than artifacts deeply rooted in camerahardware and firmware, with no direct connection to the objects imaged. Colors aren't even defined in theNIR, of course, but the false colors can add their own mystique to digital IR photographs, and somedigital IR photographers like Chris Miekus work hard to manipulate them to their own ends.

    In all fairness, NIR images aren't for everyone. As accomplished film IR photographer Josh Putnam onceput it on RPD, "... people either love [IR photography] or just don't get it, but the ones who loveit really love it." That seems to be more true of photographers than of viewers, however. IR photographerscommonly find that their IR images generate more interest than their visible light images. Many peopleappreciate IR's fresh view of things, but it's not just a matter of novelty. IR images have a rich beauty alltheir own.

    Page Index | Topic Index

    The Digital Advantage

    Unlike ordinary films, silicon-based CCDs and CMOS sensors turn out to be quite sensitive to the nearinfrared (NIR) in the 700-1200 nm (0.7-1.2) range so much so, in fact, that some of the incoming

    NIR reflectance patterns

    Visible Light Near Infrared

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    NIR has to be filtered out in order to reduce IR contamination artifacts to acceptable levels in the visiblelight images most buyers aim to take. The usual solution is to fit digital camera sensors withspecial internalIR cut filters (IICFs). These sensor-mounted filters vary in their IR transmission spectra,but mostconsumer-grade digital cameras let enough NIR through to allow some IR photography. Despitea clear trend toward ever-lower IR sensitivities in higher-end cameras, that's still true in 2004, but it getsharder with every passing year. If you get hooked on digital IR, you may end up searching high and lowfor an Oly C-2020Z or Nikon Coolpix 900, or for the more recent 5MP Minolta Dimage 7. These

    discontinued cameras are all still quite competent by any standard, but the high prices they commandlargely reflect their extraordinary IR capabilities. No, my C-2020Z isn't for sale.

    Special external filters passing NIR while blocking most or preferably all visible light make infraredphotography possible. Film-based IR photographers have been using such filters for decades, but dauntingtechnical and financial challenges continue to keep IR film photography well out of the photographicmainstream.

    Luckily, digital cameras have changed all that. Armed with even an inexpensive IR pass filter, asufficiently IR-sensitive digital camera makes IR photography

    Eminently affordable no need for expensive IR film and developing,

    Enjoyably impromptu no need to switch back and forth between regular and IR-sensitive films,

    Easily learnable via immediate feedback in the field,

    Immensely fun for the many surprises the NIR world holds (and for all the reasons above), and

    Intensely satisfying for the serene beauty you'll discover all around you.

    With quality IR pass filters like the Hoya R72 going for as little as $24, there's hardly a good reason nottotry IR if your camera's up to it.

    Page Index | Topic Index

    Sidebar: Jay Scott's Excellent IR Adventures

    In late 1999, dpFWIWcontributor Jay Scott shared with me his first forays into the IR realm with an OlyC-2020Z:

    I got a Hoya R72 IR filter, and I love it. Taking infrared pictures could not be easier. Putthe filter on the lens, optionally set the camera to black-and-white, and go. The camera has

    enough sensitivity to IR that daylight IR photos can be taken handheld, and I was even ableto get indoor IR photos under incandescent light. White plants, dark skyI love it!

    A few months later, Jay was still at it, more enthusiastic than ever.

    IR photography with a digital camera is almost like having an IR eye. You point thecamera and look at the display, and you see what it sees. It's so much fun to peer at thissurreal invisible world that I wonder why everyone doesn't!

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    Most infrared photos are made either outdoors or in a studio. But incandescent lights areIR-bright, and I found it easy to make IR photos in ordinary indoor lighting. You have tobe prepared for exposure times up to one second, depending on how bright the room is, butit's not a problem if you have camera support. Because incandescent lights are redder thandaylight, the "infrared effect" is stronger indoors, at least with my Hoya R72; you areeffectively photographing using longer wavelengths than you would outdoors. Householdobjects can surprise you with their weird appearance in IR; my blue dishwashing soap

    turned out to be IR-transparent.

    Plants are white in IR. Flowers are bright, but seed-heads are often dark. The sky is dark,but clouds are bright. Skin looks strangely smooth, which could be an advantage for someportraits. Any object which is hot enough to glow red is more than hot enough to glownear-infrared. I've photographed gas flames and hot coals.

    The camera's flash is bright enough for IR macro photography with the R72. A decentexternal flash should be bright enough to take pictures at portrait ranges. Someday I hopeto get an IR flash head so I can take IR photos at night without being noticed.

    Check out Jay's IR photos and commentary.

    Page Index | Topic Index

    Near, Not Far IR

    Let me emphasize here that digital IR photography typically relies on reflected NIR from sources like thesun and incandescent lamps. Digital camera sensors based on silicon are notsensitive to the far (thermal)IR wavelengths (typically 3.0 and longer) emitted by objects at room to body temperatures. Heat leaks

    from houses aren't visible in the NIR, and people, animals and other objects at room to body temperaturesdon't glow in the NIR any more than they do in visible light. To photograph them in the dark, you have toprovide proper NIR illumination using a suitably equipped camera like the Sony DSC-F7x7 or an externalNIR-only flash with no filter.

    This article doesn't have much to offer on NIR-illuminated night photography, but many other web sitesonly a Google search away address this rich and useful field.

    Page Index | Topic Index

    The IR Look

    Digital and film IR photographs have a look many describe as surreal. Clear, serene, bold and tonal areadditional words that come to mind, at least for landscapes. Physical and firmware-related factorscontributing to the IR look are discussed below. Aerial and reconnaissance photographers have longvalued the often stunning clarity characteristic of IR photographs, and it tops my list of IR virtues as well.

    Clarity

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    IR images owe their great clarity to the atmosphere'sexceptional transparency in the NIR. Scattering by airmolecules is much less efficient at NIR than at mostvisible wavelengths. As a result, NIR photons take onaverage a much straighter path from object to CCD.

    In visible light (left), scattering severely limits detail

    on the more distant portions of the far hillside in thishazy afternoon scene. Removing visible light withaHoya R72 IR filter takes out much of the detail-scrambling scatter. An impressive amount of detail shines through the haze in the IR image on the right,despite the odd false-color scheme.

    Usually monochrome or nearly so, IR images also partake of the deeply tonal beauty typical ofblack-and-white photographs. In combination, these visual charms make for some truly stunning IR images. To seefor yourself, take a moment now to browse the galleries in Beyond Red..., a site created by talentedlandscape photographer and dpFWIWcontributor Carl Schofield.

    Page Index | Topic Index

    IR Performance in Digital Cameras

    Before rushing out to buy an IR filter, test your camera to make sure it can do its part.

    On this page

    Can Your Camera Handle IR?

    What Makes a Good IR Camera?

    Internal IR Cut Filters

    Honey, Where's The Remote?

    IR-Sensitive Cameras

    Less Sensitive Cameras

    Topic Index

    Last updated October 22, 2009

    Can Your Camera Handle IR?

    Warning! Some digital cameras are better suited to IR work than others, and a few are downrighthopeless.

    Ever since 3 MP CCDs hit the consumer scene in late 1999, digital cameras have varied widely in their IRperformance, but the overall trend has been toward lower and lower IR sens...

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