Infrared photography tutorial
Time for a journey beyond the visible
Passionate about this technique, I have concocted a complete infrared photography tutorial for you, from theory to post-processing. You will learn in this tutorial the physical properties of light, the sensor modification needed to allow your camera to capture infrared signal, the camera settings to shoot correctly and the post-processing steps to edit your RAW files.
My portfolio of infrared pictures show you all the potential of this technique. You can discover it clicking HERE.
The visible spectrum goes from 400nm (blue) to 800nm (red). Near infrared is the part of the light spectrum between 800nm and approximately 1µm. Beyond that is deep infrared radiation, used in thermal imaging.
Infrared radiation, although invisible to the naked eye, can be captured by the sensors of digital cameras. Digital infrared photography therefore aims to capture the infrared radiation of a scene while cutting off the lower wavelengths in varying proportions.
The pictures taken with an infrared filter cutting at 720nm, for example, offer white tree leaves, creating dreamlike landscapes.
Nevertheless, to achieve a correct result, some hardware and software modifications are to be expected. For this tutorial I used a full spectrum Canon EOS 50D camera and a Canon 16-35 F/4 IS lens in front of which I screwed a Hoya R72 filter. The photos having been processed in Lightroom and Photoshop.
Essential hardware modifications in infrared photography
As mentioned in the introduction, the sensors of digital cameras can capture infrared radiation. In practice, however, a filter cutting light above 720nm, called a hot mirror, is placed in front of the sensor. Three methods are then possible to take infrared photos:
Use of an unmodified camera associated with an IR filter screwed on the lens. This method is the least expensive and will only require you to purchase an infrared filter.
However, the hot mirror filter placed in front of the sensor involves very long exposure times. For example, with a Canon 5D mark II in the middle of a sunny day, an exposure time of 30s at 400 iso is necessary to obtain a suitable exposure.
This method therefore has some disadvantages: use of a tripod for long exposures, significant chromatic aberrations, digital noise and additional risk of hot spots with certain lenses.
Use of a modified digital camera with internal built-in infrared filter. This modification replaces the hot mirror in front of the sensor with an infrared filter.
The IR filter is therefore not screwed onto the lens here, making it impossible to change the filter and therefore the wavelength. So the choice of the IR filter is essential.
This method allows you to take pictures handheld and to be able to frame via the optical viewfinder of your reflex camera.
Use of a modified digital camera with full spectrum conversion. This is the solution I use: the infrared cutting filter in front of the sensor is replaced by a clear filter allowing the entire light spectrum to pass.
Just like the first method, an IR filter has to be screwed in front of the lens in order to select only the infrared light. The IR effect can then be changed by simply choosing the type of IR filter used.
However, framing through the optical viewfinder is no longer possible, the human eyes not being sensible to infrared rays. But the add of Live View function on most cameras removes this restriction.
How to choose the right infrared filter?
In infrared photography, the choice of IR filter directly impacts the rendering your photos will have. The most commonly used filter is the Hoya R72 filter cutting at 720nm. The equivalent model from Kolari Vision is also a good choice and also has an anti-hotspot coating. Finally, the Heliopan 695nm filter offers a little more nuance in the whites tones. With these filters, the leaves of the trees appear completely white and the sky is adorned with a deep blue.
With wavelengths below 700nm, allowing part of the visible spectrum to pass in addition with infrared light, the leaves of the trees can take on a yellow-golden hue depending on the setting of the white balance. Wavelengths beyond 800nm are only suitable for black and white photography.
For this infrared photography tutorial I use a Hoya R72 filter. However the post-processing is similar for lower wavelengths. I also wrote a second tutorial about color infrared photography at 665nm.
Post-processing steps required in digital infrared photography
Post processing is needed in order to obtain a good result in IR photography. The first step is essential because it directly influences the infrared effect: adjusting the white balance. For this reason I advise you to shoot in RAW format, which allows you to manually adjust this parameter with your editing software.
Another method is to use a custom white balance obtained by shooting a neutral gray card. In this tutorial I take the example of a photo taken with an automatic white balance, and therefore requiring a manual modification in Adobe Lightroom. In the case of a custom white balance, this first step is not an obligation.
I set the white balance as follows:
- Temperature: -2000K
- Tint: between -40 and -30 (720nm filter)
The tint value depends on the period of year: with a spring-summer sun, I set it between -40 and -35; in summer-autumn between -35 and -30. The hue serves as an adjustment value so that the blue and red components of the RAW file’s histogram are superimposed. The following image illustrates from left to right the rendering of the RAW of a photo taken at 720nm SOOTC, after correcting the white balance and after reducing the exposure:
I apply the lens correction profile, export the RAW in 16bit TIFF and switch to Photoshop. At this step, we will invert the red and blue channels of the RGB colour space in order to obtain a blue sky. This will also lead to increase the whiteness of the leaves. The procedure to follow is as follows:
- Open the « Channel Mixer » tool.
- Select the « Red » channel, change the « Red » gauge from 100 to 0 and the « Blue » gauge from 0 to 100.
- Select the « Green » channel, change the « Red » gauge from 0 to 50, the « Green » gauge from 100 to 0 and the « Blue » gauge from 0 to 50.
- Select the « Blue » channel, change the « Red » gauge from 0 to 100 and the « Blue » gauge from 100 to 0.
The photo obtained is very close to the final result, but lacks contrast. I use luminosity masks to significantly increase this parameter:
The final result obtained after cropping is the following:
The sky is blue, the trunks and branches are brown and the leaves are white: the white balance has been correctly adjusted.
Conclusion of this infrared photography tutorial
Now you are ready to practice digital IR photography in the best conditions. If you need any additional information, feel free to comment this article.
If you want to use some of the pictures in this article for illustration or commercial purposes, contact me directly by presenting your needs and the desired types of use. I will get back to you as soon as possible with a suitable commercial offer.
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