Friday, October 23, 2015

Digital Infrared Photography - A Brief Introduction

Daisy. Color infrared  Macro.

Infrared or ‘IR’ photography is a small but growing photographic niche that allows photographers of all abilities and budgets to expand their skills, augment their artistic vision, and create unexpected and exciting images that cannot be captured in other ways. For the landscape photographer, IR photographs capture surreal images hallmarked by white foliage and dark skies – images that are at once familiar and unfamiliar. With a few manipulations, the sky can be blue and he foliage can be golden, lavender, or red. Black and white IR landscapes are striking even when the trees are bare. 

Architectural photographers are employing IR methods because the black and white images are contrasty and they often resemble high quality architectural drawings. Because IR light is reflected differently than full spectrum light, IR photos often reveal architectural details that are masked in visible light photography.

Lake Avalog near Hillman Michigan.
A growing number of wedding photographers are creating dreamy high key and IR fantasy photos as a value-added service. Fine art photographers use infrared photography to produce unique low key studies of shape and light and portrait photographers use IR to create flattering high-key images (and some creepy images) featuring dark eyes and porcelain skin. Even macro photographers are employing IR methods to capture eye-catching images of flowers, technology, and insects.

The reason for the growing appeal of IR photography is the widespread availability of IR-capable digital cameras. IR film was touchy, relatively expensive, and often difficult to use. The IR learning curve was steep in the film era because it could take days to realize you screwed up the shot. With digital cameras, the “shoot, evaluate, adjust” cycle can be performed immediately after the image is captured. Immediate feedback allows photographers to acquire knowledge and experience more quickly than they ever could when shooting IR film. In addition, it’s cheaper to climb the learning curve with digital photography because there is no film to purchase and develop.

How do I get started?

Like any form of photography or art, your reaction to IR photography is a matter of personal taste. Some people love it; some can’t stand the “look” of an IR photograph. I strongly urge every wannabe IR photographer to examine a wide variety of infrared photographs before they start spending money on new equipment. Looking at a variety of IR images is not only enjoyable, but it can shorten the learning curve by allowing the neophyte to concentrate on an IR style or look they find most appealing. To get you started with IR photography, I have included some gallery links at the end of this article.

The next major thing you will need is a RAW processing program and some photo manipulation skills. If your usual photographic style is to shoot JPGs and you are driven to “get it perfect in the camera” you may become frustrated by the IR photography experience. With very few exceptions, most IR photographs have to be manipulated after capture. One major reason for image manipulation is white balance. Only a few older Nikon cameras are capable of accepting a custom white balance that works for IR photos. Therefore, Nikon camera users must shoot RAW images and set the white balance with external software. In addition, most IR photos are dull and flat right out of the camera and adjustments are needed to make them presentable. The blue and green sky effects are created in post-processing. That said, LifePixel now has a hybrid filter that gives blue skies right out of the camera.

For those who are primarily interested in gear, this is where the good stuff starts. There are two primary methods for creating IR photographs - attaching an external IR cut filter to your camera lens and putting the cut filter inside the camera. An external filter allows the photographer to use their camera for normal photography when the filter is removed. IR conversion voids the camera’s warranty and after conversion, the camera becomes a dedicated IR camera.
Screw-on R72 filter.


External IR filters are usually a good place to start for most new IR photographers because filters are less expensive than camera conversion. External filters also have some challenges. The first challenge is that the filter is opaque to visible light and once the filter is attached, the photographer can’t compose or focus accurately through the viewfinder. Most filter users shoot in manual mode, set their composition and focus, and then attach the filter. The second challenge is that the filter reduces the amount of light striking the sensor by 5-7 stops. This means that longer exposures are necessary to get a good exposure. You can compensate for longer exposures by increasing the ISO, but that will eventually produce more sensor noise. Another major complication is that longer exposures contribute to motion blur. Photographers who use external filters will need a sturdy tripod to produce the best results. The last major challenge is setting the white balance and color rendering. Despite these challenges, many wonderful IR photographs have been created using external filters. External IR filters work especially well for studio work, for creating silky flowing water effects, architecture photography, and for landscape shots on a calm day.
The standard IR filter is the Wratten #89B filter which blocks 50% of the incoming light with a wavelength shorter than 720 nm. Also known as the Hoya IR72 or the Heliiopan RG720, this filter produces excellent IR photographs. Stronger filters including the Wrtten #87 (Hoya IR80 or Heliopan RC800) will eliminate 50% the light with wavelengths shorter than 800 nm are also available but the filter price is generally higher.

Exposure times will vary depending upon the type of filter, the sensitivity of the camera sensor, the strength of the IR blocking filter in the camera, and of course, the amount of IR light. That said, exposure times usually range from 10 seconds to 120 seconds for photos taken on a sunny day.

The last option for IR photography is to have a DSLR converted for exclusive IR use. This is more costly, but it produces the best results and offers the most photographic flexibility. This option involves camera disassembly and removal of the IR blocking filter that sits in front of your DSLR’s sensor. The IR blocking filter is replaced it with a filter that blocks visible and ultraviolet light. What are the benefits to this approach? The major advantage is that you can use your DSLR just as you do today. Exposure values and shutter speeds are similar to the values used for visible light images and you won’t have to waste time prefocusing and attaching the filter before shooting. And with a converted camera, you can shoot moving objects. As an added bonus, the conversion process removes the anti-aliasing filter that sits in front of the sensor. This can give your images a little boost in sharpness.

The disadvantages of using a dedicated IR camera are increased cost, the inability to use the converted camera for anything other than IR photography, and voiding your DSLR’s warranty. I got around my warrantee phobia by converting an older D90 that was sitting, mostly unused, in the closet. Once you decide to convert a DLSR, you will likely experience a bout of ‘analysis paralysis’ trying to decide which filter to have installed. This is where the Infrared Photography Forums are invaluable. There, you can ask a group of experienced IR photographers which choice they made and why.

What About Lenses?
Here’s a conundrum that may set your Nikon Acquisition Syndrome into a tailspin - some of Nikon’s very best lenses can be total duds for infrared photography. The major problem is hot spots. A hot spot is an area in an image (usually in the center) that appears to be lighter or brighter than the rest of the image. Hotspots can also produce color shifts in the image that are difficult to remove in post processing.

There are several reasons why hot spots occur, but the most common culprit is the black coating on the inside of the lens barrel. This coating is designed to absorb stray light and keep it from bouncing around within the lens. Lenses are designed for visible light photography and the coatings are well tested for that use. However some coatings don’t work well for IR light and the reflected light can produce a hot spot. Certain lens coatings can contribute to hot spots in the much same manner.

To confound the hot spot issue, there appear to be camera-related conditions (e.g., reflective microlenses or sensor elements) that conspire with lens designs to create hot spots when the aperture gets smaller. Camera specific contributions may be one reason why some lenses have different in hotspot reports in different lens databases. In general, the Nikonians IR lens database provides an excellent initial resource for determining if your Nikon lens has hotspot issues. Websites from Kolari Vision, Nasim Mansurov, and Bjorn Rorslett provide even more IR lens compatibility information for Nikon lenses and lenses manufactured by other companies. Some of the more popular “good performer” lenses include the Nikkor 18-55mm, the 18-200mm, and the 16-85mm VR lenses.

Another lens challenge is focus shift. Light bends when it passes through a lens and the amount of displacement depends upon the wavelength. Ultraviolet light bends the least while infrared light bends the most. Modern lens designs compensate for light bending and they are able to perfectly focus the middle of the spectrum on the sensor surface. Unfortunately, this means that the infrared light is back-focusing when the viewfinder says the image is in focus. Focus shift is especially problematic when wide angle lenses are used. (Wide angle lenses are the most ‘bendy’ lenses in your kit. They generate much more focus shift than long focal length lenses.) From a practical standpoint, this means that you have to focus on objects in front of your subject in order to get a well-focused IR image. Older lens designs with a distance scale often have a dot or bar indicating the infrared focus point for images that would normally be captured with infinity focus. When reputable IR conversion services alter a camera, they will adjust the focus calibration to compensate for focus shift. This calibration is done at a single focal length and the farther you go from that calibration point, the more focus error you will accumulate. Live View can compensate for this type of error because the focus engine uses the sensor image rather than the visible light image to control the focus. Stopping down can also compensate for some of the accumulated error by increasing the DOF. For most lenses, the best focus compensation is probably achieved at f/8 to f/11.


Some Parting Remarks

The ability to photograph an unseen world existing just beyond our normal perceptions seems like something right out of the Twilight Zone. However, IR photography is not an imaginary process. It’s available now and it offers exciting vistas for photographers who want to flex their creative muscles
Links to Infrared Photo Galleries and Discussions
Flickr Group Infrared

Flickr Group Magical Infrared

Flickr Vincent Versace IR Photos (mostly people)

Chris Maher - Fine Art Infrared Gallery

Don Ellis – IR Galleries are at the bottom of the page

Daniella - Infrared Landscapes

Dr. Kiss Ákos Zoltán– Infrared Landscapes with an external filter

LifePixel Infrared Photo Galleries

Bill Naiman Infrared & Digital Art Gallery

Kathy Cavallaro’s Infrared Gallery

2 comments:

  1. There is a cool application, which has repeatedly rescued me. If you have the contrast, color saturation image that lacks something NIR Color can greatly help out (but it mobile only, for PC will be great https://macphun.com/tonality )

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  2. I am a newbie. I have been reading blogs and experiementing with my camera different tricks to capture great images. A professional photographer introduced me to Trick Photography and Special Effects E-Book + Video Course. It helped me developed stunning shots and provides a lot of tricks and tips. It's very enjoyable to read. You can check this site http://bestdigitalcameraoutlet.com/photographytricks/ for more information. Hope this helps.

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