Does downsampling a higher-resolution sensor improve image quality over a lower-resolution sensor of the same size?
Asked 12/12/2013
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If two camera sensors are the same physical size, but one has many more pixels than the other, can the higher-resolution sensor produce a better final image when its output is downsampled to match the lower resolution? For example, if a 41MP sensor is reduced to about 5–8MP, would that generally look better or worse than using a native 5MP sensor of the same size, assuming good downsampling and no cropping?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
12y ago
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The pixel reduction from 41 to 8mp has the impact of improving the accuracy of colour capture and reducing the appearance of sensor noise since for each output pixel you've got a handful of pixels to calculate the best value. Obviously there's a tradeoff that you've got less spatial resolution and it comes down to what makes for the most pleasing image in the end.
Digital supersampling systems aren't new. Fuji's Super CCD cameras (like the 2002 S2 Pro which sampled 12megapixels but output at 6) were widely applauded for the quality of their colour reproduction/tonal range compared to their Nikon & Canon peers.
According to reviews the output between the likes of the Lumia 1020 and iPhone5 tend to be comparable under good lighting. But PureView devices generate better output in the kind of challenging situations where people are less likely to be carrying a camera with a larger sensor. In practice the whole system performs as well or better than a native 8mp sensor in a similar package.
The maths & physics involved mean that beyond a certain pixel density there are diminishing returns. Probably Nokia are very much at this point but the scope for improvement might be more about their processing than goosing the pixel density much further.
Originally by user14028. Source · Licensed CC BY-SA 4.0
user14028
12y ago
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Often yes, if it is done well. Downsampling a higher-resolution capture can improve the final lower-resolution image by averaging multiple sensor pixels into each output pixel, which can reduce visible noise and improve color accuracy. It can also act like a very effective digital anti-aliasing step, helping reduce moiré and jagged artifacts more cleanly than a physical optical low-pass filter.
The tradeoff is that the final image still has only the lower output resolution, so you do not keep the extra spatial detail after downsampling. Also, benefits depend on the quality of the sensor, processing, and lighting; it is not automatically better in every situation.
In practice, supersampling approaches have been used successfully in cameras and phones, and they are often praised for cleaner output, especially in lower light. So, for two same-size sensors, a higher-resolution sensor that is well downsampled can produce a more pleasing low-resolution image than a native low-resolution sensor, though the result depends on implementation.
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