Contrary to conventional wisdom, higher resolution actually compensates for noise
Sunday, November 16, 2008 News| Introduction | Modeling small pixels | Comparing the SNR of cameras with different resolutions | Real-life comparisons | Conclusion |
The argument above provides a method to compare cameras with different resolutions. A high-resolution camera can still be turned into a low-resolution camera by averaging its pixels.
In
order to compare all cameras and not just pairs, a reference resolution can be
chosen and equivalent SNRs at this resolution are computed. Let Nref
denote this reference resolution. Consider a camera with N Mpix. To
obtain an image with Nref pixels, N / Nref
pixels need to be averaged out to produce a single pixel in the output image,
so the noise decreases by a factor of 
.
We then deduce that SNRref at resolution Nref
can be obtained from the nominal SNR (in dB) using the formula
Notice that if the reference resolution Nref is very large, or if the initial sensor has a low resolution, the normalized SNR can actually be lower than the nominal SNR.
Further readings for the Contrary to conventional wisdom, higher resolution actually compensates for noise
To provide photographers with a broader perspective about mobiles, lenses and cameras, here are links to articles, reviews, and analyses of photographic equipment produced by DxOMark, renown websites, magazines or blogs.
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The new "advanced compact" category that adds DSLR features (such as RAW output, manual operation, and interchangeable lenses) to classy, compact-style cameras, continues to be populated with new models—e.g., Canon Powershot G11 and S90, Olympus EP1 and EP2, Panasonic GF1, Leica X1, etc. |
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On DxOMark, we evaluate and rank many types of digital cameras with image sensors that vary widely in pixel count, pixel size, and digital signal processing. To ensure that sensor performance comparisons between cameras are fair, it is very important both to test under identical shooting conditions and to take viewing conditions into account. |