French photographer Mathieu Stern is well known for his “weird” cameras and lenses, and one such is Stern’s converted full-spectrum Sony Alpha 7 II. Stern recently visited London with it and documented the experience of using it for travel photography.
The experienced folks at Kolari Vision modified Stern’s Alpha 7 II. Kolari offers a wide range of camera conversions, including ones like Stern’s, that accept clip-in filters to capture images at different wavelengths.
In Stern’s case, he used these clip-in filters — including IR830, IR590, and IR Chrome — to dramatically change the look of his photos. He tells PetaPixel that, “my favorite infrared filter right now is the IR Chrome filter from Kolari Vision. It makes the vegetation a vibrant red and keeps the other colors natural. The sky stays blue, and people’s skin is not affected too much.”
For photographers who want to simulate infrared photography without having their camera modified, Stern offers an infrared look-up table (LUT) to allow editing apps, including video editors, to transform green foliage into the trademark red of infrared photography.
“Because converting a camera to full-spectrum can be very expensive, I created an Infrared LUT for people who want to play with the infrared look but don’t want to modify their camera,” Stern tells PetaPixel.
While not without its limitations, “The LUT gives you a very good result on photos and videos. You get vibrant red foliage, and the sky stays blue.” Users can adjust intensity and hue when using Stern’s Infrared LUT in Photoshop and Premiere Pro.
A real modified camera will allow users to achieve similar results in-camera. However, Stern observes that post-processing is often required to achieve the best results, even when using a full-spectrum camera and the filter of choice.
Nearly all cameras arrive to customers with an infrared-cut filter in front of the image sensor. This is important for most typical photography applications, as it allows the camera to see only visible light. Without an infrared-cut filter, images would have unexpected and unusual colors.
A typical human eye sees light from 400 to 700 nanometers (nm). This wavelength is called “visible light.” Cameras come with a filter designed to eliminate wavelengths of light outside the visible light range. After all, most photographers want to capture images that look like what they can see with their own eyes.
If a camera is modified not to have an IR-cut filter, its sensor can capture light from a much more comprehensive range of wavelengths, going from as low as 300nm (ultraviolet) to 1,100nm (infrared). However, if a sensor is hit with all that light, it needs to be controlled somehow, or images can appear blurry and soft. Different wavelengths of light don’t focus at the same point.
The clip-in filters Stern uses on his modified full-spectrum a7 II limit the wavelengths of light that reach the image sensor, which dramatically changes the appearance of colors. For example, his IR590 filter makes green foliage look yellow and blue skies darker and bluer. An IR Chrome filter allows visible and infrared light through to make green look orange.
Each wavelength offers different visual effects. Stern says that it’s vital that photographers understand different infrared wavelengths and how various filters change the look of their photos.
“The main challenge with a full spectrum camera is choosing the right filter for the occasion. It’s important to know beforehand where and what you will shoot,” Stern remarks. “Some places will look very good in red but boring in black and white, while others will reflect more infrared rays than others. The contrast between natural and architectural elements also looks different depending on the filter you choose.”
Companies like Kolari Vision offer multiple conversion options, including infrared and full-spectrum. A full-spectrum camera provides more possibilities than an infrared camera, including use for ultraviolet and astrophotography. An infrared conversion limits a camera to a specific infrared wavelength.
“For me, infrared photography is a way to have fun in places that would maybe look very boring,” Stern tells PetaPixel. “I love experimenting with photography and new techniques, and my YouTube channel is all about that.”
Photographers seeking to modify their cameras can mail them to companies like Kolari Vision for conversion. Kolari also offers conversions specific to astrophotography and agricultural monitoring. Stern recommends that photographers know beforehand what they will shoot and how it might look with a converted camera. He also says it’s a good idea only to convert a backup or secondary camera you don’t need for typical photography.