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The Easy Guide to Understanding Infrared Photography

The "What's" of  Infrared Photography

Infrared photography is a look into the invisible world. In infrared photography, the scene illuminated by infrared light is captured using a camera. This produces some very distinct effects which make photographs aesthetically pleasing. 
Surrealistic effects produced when IR comes into contact with plants and grass are very popular among landscape photographers.

Some subjects like
the sky, water, foliage, human skin, some dyes and fabrics will appear different when viewed in infrared light. The most striking difference is the “Wood Effect”, an effect where leaves reflect light giving them a bright white look. (Note that Infrared photography has nothing to do with thermal photography, which need a specialized thermal camera.)

Visible light ranges from 400 nm (violet/blue) to 700 nm (deep red). Wavelengths above 700 nm and up to about 5000 nm are known as near infrared.

The CCD and CMOS sensors used in digital cameras today are sensitive to light with wavelengths up to around 950 nm. However, for standard photography, capturing infrared light is not desirable, so the manufacturers put an IR-blocking filter in front of the camera's sensor. The IR-blocking filter limits the sensitivity of an unmodified camera to wavelengths below 700-705 nm.

The "How's" of  IR photography 

There are three general ways to do IR photography.

Infrared film:

This was the first method developed and for a long time, this was the only way to shoot infrared. This required specialized film, the use of an infrared filter over the lens, and specialized developing. This can still be done today, but the film is hard to find.

Infrared portraits have unique effects such as white and smooth skin and coloured hair.

Black and white conversion of infrared portraits are even more appealing due to inherent lowkey effect.

Digital camera with an external infrared filter:

This is possible because modern digital sensors are sensitive to wavelengths between 300 and 1200nm.  To preserve the color fidelity for normal photography, manufacturers have integrated “IR Cut filters” over the sensors to block UV and IR. These filters are not perfect, so by placing a 720 IR filter on the lens and taking a long exposure, you can take infrared photos on some cameras. Pros: The cheapest way to try infrared. Cons: Long exposures require a tripod, motion blur, exposure and focus bracketing, fewer filter options.

Infrared converted camera:

Infrared converted camera: By removing the IR cut filter that is over the sensor and replacing it with an IR pass filter, the camera becomes fully sensitive to infrared. This infrared conversion removes the need for long exposures and lens filters. Pros: Normal exposure times, using the camera like normal, more filter options, sharper results. Cons: Pricier than a filter.

External infrared filter vs infrared conversion

With digital cameras, infrared photography is still possible without any modification. Digital cameras are sensitive to infrared light and contain an internal filter that blocks infrared light. Infrared photography is possible on these cameras with an external infrared filter like 720nm filter, but when doing this keep in mind there will be two filters in the light path. One filter blocking infrared light at the sensor, and the external infrared filter blocking visible light. These two filters tend to cancel each other out, requiring very long exposure times to get a properly exposed picture. The external opaque filter also makes composition on a DSLR difficult and requires the use of a tripod for the long exposure times. This makes it impossible to take clear infrared pictures of moving objects.
In an infrared conversion, the camera’s internal hot mirror is removed and replaced with a filter that only lets infrared light through. This makes a camera much more sensitive to infrared. This allows handheld infrared shots to be taken with normal exposure times and low ISO. There is no more need for filters in front of the lens, allowing for easy composition and lens switching. A converted digital camera is the only way to take good digital infrared portraits as the subject no longer has to stay perfectly still for a long exposure. Putting the infrared filter inside the camera instead of on the lens allows you to use the autofocus as well. An infrared conversion also allows more filter options, like the 590, 665, and blue IR, which do not work on stock cameras.

Choosing an Infrared Filter

What filter to pick for IR photography is depend on what infrared effect you want to produce. If you pick a filter with a too low pass point, you may be unable to produce the infrared effect. If you pick a filter with a too high pass point, you may not be able to capture enough light to produce a photograph. You may need to experiment to find a filter that is fit for your camera and for a particular task. Usually, for most cameras, infrared effects appear around 720 nm. That includes water going dark, foliage going bright, and human skin becoming translucent and showing veins.
The following table below shows a number of popular filters available on market:

Standard Filter Choices

Standard (720nm) Filter: Standard Color IR filter (720nm - R72) which allows the camera to capture all Infrared Light and a small amount of visible or color light. This filter will produce great Black & White images simply by desaturating the image in Photoshop.
Amplified Color IR (665nm) Filter: Amplified Color IR Filter (665nm) which allows all Infrared Light and more visible or color light than the Standard filter to be captured by the camera. This filter will produce good Black & White IR images simply by desaturating the image in Photoshop. Some additional adjustments may be needed to achieve the best Black & White results.
Extreme Color IR (590nm) Filter: Extreme Color IR (590nm) filter allows a very large amount of color as well as all of the IR spectrum to be captured by the camera. Example images using this filters are included in the gallery at the top of this page. This filter will produce good Black & White IR images simply by desaturating the image in Photoshop. Some additional adjustments may be needed to achieve the best Black & White results.
Black & White IR (830nm) Filter: Black and White (830nm - 87C) filter which allows only Infrared Light to reach the imaging sensor of the camera, creating deep, rich, black and white images with little to no post adjustments. For the purest black and white IR shooter, this is the filter of choice.
The image below shows a comparison of the effect produced by these filters:
Infrared Filter Options and IR Image Comparisons (Credits: Spencers Camera)

Sample photos

(All the following clicks are the copyright property of Basil Mathai, any unauthorized use is strictly prohibited). The photos are taken with converted canon 1200D, with 590 nm extreme color filter.

Further readings

Digital Infrared Camera Modification Tutorials: https://www.lifepixel.com/tutorials/infrared-diy-tutorials
Infrared Photography, Basics, How to: http://ir-photo.net
Post processing Infrared Photography: https://www.capturemonkey.com/redblueswap-lightroom-profiles

The Easy Guide to Understanding Infrared Photography The Easy Guide to Understanding Infrared Photography Reviewed by Unknown on Friday, August 17, 2018 Rating: 5

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