Check Out What A Big Difference The iPhone 4S Camera’s IR Filter Makes



Infrared light. We can’t see it, but it surrounds us, permeating everything… especially our digital camera sensors, leading to images filled with off, unnatural colors.

With the iPhone 4S, Apple introduced an infrared filter to improve color quality in the images. But what are the practical effects of this filter? Much more accurate color and the elimination of the reddish tint that plagues so many iPhone photos.

Over at Camera Technica, there is a great overview about how infrared affects image quality, and why Apple’s IR filter leads to so much higher quality photographs. Here’s an overview:

When IR light is allowed to pass through to the sensor, the IR light contaminates the channels (mostly the red channel) with information that was not visible in the original scene. The result is an image with a color cast. The images below show the impact of IR contamination on a scene with a dark background. The iPhone 4 image shows a reddish cast due to the extra IR light recorded on the red channel. The 4S image shows a background which much more closely resembles the original scene.

This sort of filter is especially important for the iPhone 4S, because there’s no other way to accurately eliminate the IR contamination otherwise. On SLR cameras, you can muck around with RAW files to fix things up, but on an iPhone, everything’s preprocessed into JPGs, meaning all adjustments need to happen in-camera.

Just another example of Apple putting a lot of thought into the small details no one else ever notices.

  • PaulG

    Are those photo lables round the right way? The iPhone 4s picture looks very red

  • Algr

    Adjusting the RAW files is not a reliable way to correct for infrared, because different objects reflect different amounts of IR.  I have a black bag that I shot when experimenting with IR photos. In visible light, the whole bag is black, but in IR, only the handle is black, the rest of the fabric is grey.  So IR contamination can let you see things that simply aren’t there.

  • JustinM

    The background on the left picture is more red, but the blacks are a lot richer, deepr and true. The picture on the right has a greenish grey tinge and the whole thing looks desaturated. I prefer the image on the left and wouldn’t be using this set of pictures to show the 4S camera is ‘better’. Look at the red spot on the lens on the right hand picture. It looks almost yellow and is more unnatural than the picture on the left.

  • Sam

    I’m pretty sure these must be around the wrong way? The photo on the right looks much worse?

  • Osirus66

    Years from now they’ll be a 3rd party app to put the infra red info BACK in the photo.

  • Chase Brownell

    Why do you never link back to the original article? I love that you aggregate news, but please at least allow me to read the original without starting a separate google hunt.

  • iDaBoss

    both images look terrible