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Quantum Film Might Replace CMOS Sensors
An anonymous reader writes "Quantum film could replace conventional CMOS image sensors in digital cameras and are four times more sensitive than photographic film. The film, which uses embedded quantum dots instead of silver grains like photographic film, can image scenes at higher pixel resolutions. While the technology has potential for use in mobile phones, conventional digital cameras would also gain much higher resolution sensors by using quantum film material." The original (note: obnoxious interstitial ad) article at EE Times adds slightly more detail.
There is a physics problem when your image sensor is too small - photons have size and mass, and there is a point at which you cannot collect enough light to take a good picture.
That's why expensive cameras have larger image sensors - they aren't packing more pixels per square inch, they are actually packing fewer pixels per square inch. A high end 10 mega-pixel will have an image sensor that is 10x bigger than a pocket-sized 10 mega-pixel camera, and it will take phenomenally better pictures.
This is the source of the GP's confusion about what the summary means - is "quantum film" more sensitive to light? Or are they simply able to pack more sensors in a smaller area? If they are actually able to collect accurate color information from fewer photons (i.e. more sensitive to light), then you can shrink the size of high end image sensors and still maintain quality. If it simply allows them to pack more pixels onto a sensor without being able to collect accurate color data with fewer photons, then quantum film is absolutely worthless. It offers no benefit to the quality of images in that case, even if they can crank a camera up to 30 megapixels it will still look like shit.
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller
No, it doesn't. The lens system of the camera only has a certain resolving ability. Once you pass that point, you can make the sensor as high resolution as you want and you're just wasting your time because the lens isn't passing information at that level of detail anyway. Basically, you're measuring blur more and more finely.
Take a picture from anything less than a high end SLR or medium format camera and zoom in until you're actually looking at one image pixel to one screen pixel. Now tell me how good the image looks. Pretty crappy, hey? That's because the lens isn't capable of producing a decent image at even the resolution of the current sensor, never mind a better one.
This is about the laws of physics. I'm sure somebody will correct me if I'm not explaining this very well, but...
There's a limit to how precisely a lens can focus light. Now, in theory, as the aperture gets smaller, the diffusion decreases, so you might think that the small lenses would be result in a more precise image than larger ones. However, with those smaller lenses come smaller image sensors, which means that even if the lens can focus light to a smaller point, the pixels are also smaller, thus canceling out much of this improvement.
The bigger problem is that the smaller the lens, the greater the impact of even tiny lens aberrations on the resolving power of the lens. A speck of dust on a 1.5mm lens makes a huge difference, whereas it can be largely ignored on a lens with a 72mm diameter.
Also, as resolution increases, light gathering decreases. That's pretty fundamental to the laws of physics. Think about the bucket analogy. You have four square buckets measuring 1 foot by 1 foot. You place them side by side during a thunderstorm. You get another bucket that is two feet on each side. You place it beside the others. The same amount of rain (approximately) falls onto the four small buckets as the single large bucket, thus the large bucket has four times the amount of water in it that any one of the smaller buckets does.
The same principle applies to pixels. All else being equal, resolution and light gathering are inversely proportional. Small cameras are already hampered pretty badly by light gathering because of their small lenses. Increasing the resolution just makes this worse. I can tell the difference in noise between my old 6MP DSLR and my 10MP DSLR. I can't imagine what 20MP in a camera phone would look like. :-D
I think the real question should not be whether we can make smaller cameras, but rather whether we can make existing small cameras better by improving the light gathering. This technology might do that---whether it will work better than some of the newer CMOS sensor designs that already move the light-gathering material to the front remains to be seen---but at some point, making things smaller just means that they're easier to lose. I think we're at that point, if not past it....
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