I recently had my older camera, a Sony a6000, converted for infrared photography. What this means is that the camera was modified to remove the original infrared-blocking filter that sits in front of the imaging sensor and replace it with a filter that allows infrared light to pass. Camera sensors have the ability to "see" light beyond the visible spectrum that we can see with our eyes. Digital camera sensors are sensitive to both ultraviolet and infrared wavelengths of light, so cameras are equipped with these filters to block out most of the non-visible light from reaching the sensor. Removing this filter while blocking some or all of the visible light spectrum allows us to capture captivating images of this alternate invisible world that is around us all the time.
I had my camera converted to allow light of wavelengths longer than 470 nanometers (nm) to pass, or roughly all of the visible spectrum from middle blue to red (ROYGBIV without the indigo or violet) plus the invisible infrared wavelengths. The company that converted my camera, LifePixel, calls this the Hyper Color conversion (because they already used the terms Standard, Enhanced, and Super Color). What this really means is that I can add other light-blocking filters in front of the lens to achieve more of an infrared effect to the images. For example, I have a 590 nm filter that allows orange, read, and infrared wavelengths into the camera, and a 720 nm filter that only allows in deep reds and infrared.
Why did I pick the 470 nm Hyper Color filter? Because I couldn't decide, and it provides more flexibility because I can always add an external filter to get a deeper infrared effect, but the filter inside the camera is permanent. I looked at a lot of infrared images when I was trying to decide, and ultimately I picked the option that gives me the most options. At this point, my favorite images have been shot with the 720 nm filter, but then again I've only used the camera for one day.
A few days after receiving the camera back from LifePixel, my daughter and I went out to Palo Duro Canyon to take some photos. Even though it is now late February, the junipers and yuccas still reflected a lot of IR light, and the winter sky was perfect. I had planned to shoot a lot of images using all three filters (470, 590, and 720), but in the end I really favored the 720 nm look-I used the 720 nm filter on more than half of the images and the 470 nm on only about 5 percent. I'm not surprised-I originally became interested in infrared photography because of the high contrast black and white landscapes associated with deep infrared images. Besides, mid-winter in a semi-arid canyon is really not the ideal time or place for testing of an IR camera, but I did learn a lot and came away with a few nice images.
Shooting with a mirrorless camera allows me to preview the image in the viewfinder before taking the picture. I found that regardless of the filter, I could get a good preview image by setting the picture style to monochrome with +2 contrast. In fact, for black and white images, several of the camera JPGs looked really nice. But for infrared, it is critical to shoot in RAW. Another benefit of mirrorless is that the camera autofocus still works accurately whereas a DSLR must be in Live View for accurate autofocus. This was only a partial benefit since one of the two lenses I used is manual focus (Samyang 12 mm f/2), but focus peaking and the focus magnifier in the viewfinder were both helpful. I also found that I needed about +2 EV exposure compensation regardless of the filter. I used a range of +1.7 to +2.3 EV for all of the images shown on this page with one exception using +0 EV. Going forward I'll probably stick to +2 and leave the camera in Aperture Priority.
Lens selection is another potential issue for infrared photography because internal reflections within the lens can produce hot spots in the images. I shot with the Sony 24 mm f/1.8 Zeiss and Samyang 12 mm f/2. Both lenses worked well with no hot spot issues at the apertures I was using (mainly f/5.6 and f/8).
Processing the images is possibly more challenging than the capture. The easiest option is black and white, but even for those the character of the images is greatly different from anything I've ever worked with. I ended up with more monochrome images from the day, mostly because I used the 720 nm filter for more shots and because monochromes are the easiest to process in Lightroom. But I did experiment with a few of the color images and actually produced a few that I like. Processing the color IR images is more difficult in part because I am having to learn to use processing tools other than Lightroom; Photoshop (or something similar) is essential for swapping color channels, and the Nik Collection seems to be a favorite of most IR photographers posting online. Monochrome images, either 590 or 720 nm, can be processed in Lightroom with good results. Hyper Color images can also be processed in Lightroom depending on the desired final look. But any kind of false color processing requires a more powerful editor. I plan to write some future blog posts on IR processing once I develop some better skills.
So far, I'm really happy with my decision to go with the Hyper Color (470 nm) conversion for my a6000. The Hyper Color images are the closest to reality, but with a surreal twist, while the Super Color images are definitely other-worldly. And the intense contrast produced with the 720 nm filter is wonderful. Once again, winter is not the ideal time for capturing false color imagery of vegetation, so I'll definitely be exploring more with artistic processing these in the future.