Pulling out the infrared light in a photo might clean things up, but it can't save a blurred picture. Photo credit Preston Scott
Infrared light. Good for: remote controls, keeping lizards warm, detecting Arnie in Predator. Bad for: your photos. The fix? An IR filter.
There are two kinds of IR filter — the one in your DSLR that blocks IR light, and the kind you use on a camera flash or over a lens to pass only infrared light, to spooky effect. The iPhone 4S added the first kind, improving things quite considerably.
Preston Scott, of the ever-impressive Camera Technica blog, takes a look at the differences a simple IR filter make to the iPhone’s camera. He has made a video showing the IR-blocking capabilities of the 4S’s camera next to the filter-free iPhone 4. By pointing the cameras variously at remote controls and other IR emitters, he shows that the 4S blocks IR very well.
Who cares? You, hopefully. When infrared light is allowed to contaminate an image, it pours into the camera’s sensor and fills up the red sensors. This not only gives the image a color cast, but also stops the actual red light in a scene from being recorded. This could lead to overexposure in the red channel.
With RAW files, you can probably fix things up well enough, but with the pre-processed JPGs the iPhone spits out, you want to get things right in-camera. And as you can see from Preston’s photos above, the iPhone 4S does just that.