In an interesting new approach to high dynamic range photography, a group of researchers at MIT Media Lab have developed a method of increasing a camera's dynamic range to infinity, potentially ending the problem of overexposure.
Well, mostly. Despite the news making PetaPixel and Imaging Resource (among many other photography websites), if you read the actual paper and watch the video below, you'll note that the supplied photo that is making the rounds is a simulation. Also, there are situations where this doesn't work perfectly.
So perhaps we shouldn't be hailing the end of overexposure just yet. Regardless, the concept is sound (the researchers have used the technique for grayscale images as proof-of-concept) and I wouldn't be surprised if major camera manufacturers adopted the idea at the hardware level.
So how does it work?
By putting a "counter" on overexposed pixels.
Image sensors have millions of photosites that collect light. You might think of these photosites as tiny little 'buckets', collecting "raindrops" in the form of photons.
When the bucket is "empty" (e.g. "your lens cap is still on, stupid!"), the photosite doesn't collect any photons, and the colour black is recorded.
When the bucket is "full", the photosite records white light.
Colour is recorded by using red, green, and blue photosites, and then interpolating the results.
However, once the bucket fills up completely, it "spills over". In other words, the photo site receives more 'raindrops' than the 'bucket' can hold.
And that's how you get overexposure in a photo. In technical terms, the recorded information exceeds the upper end of a photosite's dynamic range.
Up until now, we've just had to live with this.
But in the new approach -the kind that makes you think, "Why didn't someone think of this earlier?", the MIT researchers created a counter for each photosite, so that when it fills up, it resets and begins recording anew.
Watch the video below explaining the process.