An Introduction to Infrared Photography: Part 1

by Dr. Patrick Buick

Posted: May 16, 2012

Editor’s intro:  In the past, I experimented with infrared photography, which yielded a most interesting effect.  When I heard that Dr. Patrick Buick, from the Venice Camera Club, was using a converted Nikon D70 to shoot in infrared digitally, I was amazed.  Let’s take a look at what this all means, and how to get that wild look…f-stop

Photography is creating and capturing images from light.  It began as chemistry with silver-based chemicals that reacted to light, on a film on glass in a camera. This evolved into a similar process with silver-based emulsions on film.  Other chemicals were used in the darkroom to develop the film, and it was then projected into two-dimensional images on paper for viewing. Today, the light is detected by a sensor in a digital camera which convert it into electronic signals that are used to create two-dimensional images that we can enjoy with various media.

IR images have a surreal appearance, as different surfaces emit, reflect or absorb the IR light.

Physics of Light

You may think of light as a visible quantity, but most is not.  Only a small range of wavelengths (or energies) are visible to the human eye.  We see light as colors, ranging from red to blue (violet).  Just outside the visible range we find UV (ultraviolet) light, and on the other side, IR (infrared) light. And further afield are x-rays, radio and TV signals, microwaves, gamma rays and more. Google “Electromagnetic Spectrum” for more information on the frequency ranges of visible and invisible light. Photography has long concentrated on visible light, but on occasion we’ve captured 'invisible' infrared light, initially with film cameras and later digitally.  We will now focus on IR photographs using

digital cameras.

Chlorophyll reflects IR light, making for lovely images of plants, like this palm tree.

More Physics

Subjects reflect visible light; that’s how we are able to see them.  They also reflect infrared light, because it is part of total light from the sun and other light sources.  All subjects either emit light,  absorb light,  are transparent to light or reflect light. (O.K. I didn't mention “refraction” which is how camera lenses work. And IR light refracts differently than visible light.) And every substance reacts differently to light. For instance, blue subjects absorb red light and reflect blue light, which is what we see.  Since human eyes do not see infrared light, we are generally unaware how IR light interacts with a given subject. Some subjects reflect infrared to a greater degree, some less so.  Chlorophyll, a substance found in plants, reflects IR light very well, which makes for some spectacular IR images.  Interestingly, human skin looks much smoother, with fewer imperfections

in IR images.

Using a Digital Camera to Capture IR

How do you shoot IR?  Two ways:

• Use an IR filter in front of the lens. It blocks visible light, and allows IR light to pass to the sensor.

• Use a converted camera.  It has a modified filter inside the camera body just in front of the sensor, that blocks visible light, but allows IR light to pass through.

With an external IR filter, you must first compose and focus your shot before carefully putting on the filter. You cannot see the remaining infrared light through the viewfinder. The visible light is filtered out, allowing the infrared light to reach the camera sensor to create an IR image. The IR converted camera lets you use the viewfinder (or live view), because the filter is after this viewfinder light-path, but in front of the sensor within the camera.

For comparative purposes, all of the images in this article were taken with an external Hoya 72 filter, except for the 3^rd  and 5^th images, featuring the red skies and club members at the beach. These images were taken with a Nikon D70 converted by Life Pixel featuring their internal Super Color IR Filter and using a Nikkor 18-70mm f3.5-4.5G ED lens. 

Red is often very prevalent because of its proximity to IR in the color spectrum.

Generating the IR Image

The IR light information is stored inside the digital camera, ready to transfer to your computer for development into a visible image for projecting or printing.  This is the tricky part - we use software to modify the sensor data and create an image for viewing.  There is no color in pure IR images, so black and white is the easiest way to display an image. But there are many shades of gray to manipulate in the software.  Most converted cameras have a filter that allows some colored light to pass to the sensor, so color manipulations are also part of the software processing in IR photography.  The most common color that sneaks in is red, because it is closest to IR light in the spectrum.  Those red skies look better when converted to blue skies using the software. Adobe Photoshop CS5 allows you to swap red channels for blue channels in image processing via Channel Mixer, by selecting Image>Adjustments>Channel Mixer. I also use Nikon’s Capture NX2 for editing IR imagery. Lightroom4 and PSE 10 (Elements) do not have the range for acceptable IR-based channel mixing.

Detect counterfeit bills by utilizing IR photography.

The best software choices are specific to your particular brand of camera, but that discussion  must remain for subsequent articles.  This is an introduction to IR photography--not the detailed final word.  There is no “final word”, because “photography is a journey, not a destination.” But stay tuned, learning is ongoing.

I will share one small, tangible bonus to experimenting with IR photography - you can detect counterfeit money.  Real five dollar bills have a couple of vertical bands on the back that are only visible with infrared light. IR photography could keep you out of jail.

A day at the beach in IR.

Final Suggestions for IR Photography

Try the external IR filters before you convert your camera to IR exclusively. But keep in mind. external IR filters, like the Hoya 72R, don’t work very well on newer cameras, because the newer internal camera filters remove more of the infrared light before it gets to the sensor.

You can convert your old camera using equipment from Life Pixel. Use your old or secondary camera because you will be giving up color photography and black and white photography with visible light.  One of the most frequently modified camera bodies for IR is the Nikon D70; these can be found on places like eBay for $100+/-.

Stay tuned for IR Photography, Part 2: The essentials of capturing and developing images of infrared light and Advanced IR Photography: Tips and techniques for photographers who are shooting IR images.

Dr. Patrick Buick has taught Biology, Chemistry, Physics, Astronomy and Computer Science in public and private institutions and at nine colleges and universities. Although he is now retired, he cannot give up teaching and his addiction to organizing and presenting scientific knowledge.  For Dr. Buick, experimenting with IR photography is a way to satisfy his other addiction—learning.  Dr. Buick is a Nikonians gold member and a member of the Venice Camera Club.