In my earlier newsletter, I talked about how IR (infrared) light pollution can be a problem on some cameras – especially on new cinema cameras such as the URSAs from Blackmagic. Both the Minis and the full-size URSA don’t have any internal filters that will cut out infrared light.
If you are wondering if your camera suffers from the same problem, then first check if the camera has a low-pass filter. Most cameras with built-in low-pass filters also include an IR element. But if your camera doesn’t have a low-pass filter or comes with exchangeable ones, then there is a good chance that IR pollution could cause you some headaches. In the end, the best way to find out is to test out your camera.
To see if your camera suffers from IR pollution, just take a test shot without any filters; then repeat the shot but with strong ND filters.
If you see a significant shift in colors towards reds – especially in the shadows – then your camera has an IR pollution problem. Usually, this will become only apparent when using ND filters, because ND filters reduce the intensity of the visible light spectrum – i.e. the light that I and you see.
However, camera sensors actually see more light than we can. They can see wavelengths of light known as infrared. Since this light is on the warmer side of the light spectrum, it means that if you reduce the intensity of the visible light (with an ND filter) BUT not the infrared light, then your whole image will turn a lot more red.
So to prevent that, you have two options. You can get different ND filters that will block the visible light spectrum AND the infrared light. These filters are commonly known as IRND filters.
Second option is to get a clear filter that will stop only the infrared light. You then put this filter in front of your lens, together with a separate ND filter.
In the video below, you can see me test out both approaches to this problem. Hope you guys find these tests useful.
Here are the filters I used in my tests: