What does interpolation or pixel oversampling mean on the Nokia 808 PureView, and is the 41MP claim real?
Asked 2/27/2012
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The Nokia 808 PureView is advertised as having a 41MP sensor, but many descriptions say it uses “interpolation” or “pixel oversampling” to combine several sensor pixels into one output pixel. Does that mean the 41MP figure is fake, or is the sensor genuinely that high resolution? How does this oversampling work, and does it really improve image quality or zoom compared with a normal phone camera?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
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The white paper in your link explains this very nicely.
The "jiggery-pokery" that Engadget speaks of is not faking the high resolution, but rather going the other way around: the sensor really does appear to have that many tiny little photosites, but under normal use, it pixel bins. (Presumably, the image quality is pretty atrocious at the pixel-peeping level.)
Nokia says:
Pixel oversampling combines many pixels to create a single (super) pixel. When this happens, you keep virtually all the detail, but filter away visual noise from the image.
The sensor they're using is relatively big (for a compact camera) — they're saying it's a 1/1.2" format sensor, which would be a 13mm diagonal, which is only slightly smaller than the Nikon CX.
Digital Photography Review now has a blog post explaining this, with pretty pictures. One key thing that they note (and which I didn't bother to work out but should have) is that the larger sensor means that the photosites-per-area is the same as for a typical 8mpix cell phone or ultra-compact camera.
And, I'm going to re-quote something they take from Nokia's blog (the link you posted):
5Mpix-6Mpix is more than enough for viewing images on PC, TV, online or smartphones. After all, how often do we print images bigger than even A4? [It] isn’t about shooting pictures the size of billboards! Instead, it’s about creating amazing pictures at normal, manageable sizes.
I sure hope DSLR makers take that same philosophy as large-sensor cameras increase in megapixels as well. (Canon's on the right path with sRAW.)
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
14y ago
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The 41MP claim refers to the sensor itself: it really has a very high number of small photosites. The trick is that the phone usually does not output full 41MP images in normal use. Instead, it combines data from several neighboring sensor pixels into one output pixel — often called pixel oversampling or pixel binning.
That is not the same as inventing detail by interpolation. It’s more like averaging multiple samples into one “super pixel,” which can reduce visible noise while keeping most of the real detail in a smaller output image, such as 5MP.
A second benefit is zooming: because the sensor starts with so many pixels, the camera can crop into the center and still produce a reasonably detailed lower-resolution image without relying as much on digital zoom.
So the sensor resolution appears to be real, but the practical benefit is not “41MP phone photos” so much as cleaner low-resolution images and better crop/zoom flexibility. The sample images may look impressive for a phone partly because the sensor is relatively large for a phone camera, but the real test is image quality in finished output rather than pixel-level inspection.
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