Light is something that all photographers and filmmakers need to master if they want to become good at their craft. The problem is, our eyes don’t see light the same way that our cameras do. Infrared is outside of the human spectrum of vision, but it’s not necessarily outside of your camera’s, and it can cause all kinds of problems with the colour of your footage.
Infrared light has only really become a problem for photographers and filmmakers since the dawn of digital. Regular daylight film simply wasn’t sensitive to it at all, so it was never an issue. Now, though, that’s changed.
For photographers, infrared light is most commonly an issue for long exposure photographers. A lot of people go buy their first 10-stop ND so they can make those minute-long daytime exposures and then when they get home and look at the images they jump on Facebook and rant about colour casts and leave bad reviews.
The thing is, though, the filter’s doing its job, for the most part. It technically doesn’t really have a colour cast, and it’s blocking the visible light exactly as it should. What it’s not doing, though, is blocking the light we can’t see. Infrared light. In an ideal world, the filters over our sensors would block it, but they don’t. Much of the near-infrared close to the visible spectrum still gets through. Different manufacturers block it out to different degrees which is why the same filter can show different colour casts on different cameras.
The same thing holds true with video, once you start to add around 3 or 4 stops of ND over the end of your lens. And it’s not just a colour shift, either. Infrared light pollution can make an image appear muddy and even soft.
The solution to the problem is “IR blocking” or “IR corrected” ND filters. These have been around for a few years now, and as well as blocking the visible light, they also block the infrared light, offering a more natural colour when you need to reduce the light entering your lens. You can also purchase filters to stack with your existing neutral density setup to just block the infrared light, and create a more pleasing final image.
Tiffen isn’t the only company out there making neutral density filters for filmmakers and photographers that correct for infrared, but they are one of the most popular, particularly in Hollywood.
Many of those making neutral density filters designed for photography already implement IR blocking into their filters for long exposure use, but if you do start to see weird colour casts in your photographs or video footage, then infrared pollution is probably the cause. And for stills, at least, it’s quite easy to correct for with 14-Bit RAW files. But with lower bit depth video files, not so much.
How do you deal with infrared pollution? Do you use IR blocking filters or attempt to correct it in post?