Pixel density - can the playing field be leveled???

Started Jun 6, 2009 | Discussions thread
ejmartin Veteran Member • Posts: 6,274
Re: Pixel density - can the playing field be leveled???

Graystar wrote:

All of that being said, I personally have a theory that a sensor with
smaller pixels actually does produce an image with more noise than a
sensor of the same size with larger pixels. But that type of thing
is hard to prove, and it really doesn't matter because you can only
buy what manufacturers are offering anyways.

I would say it the following way. Taking the example of the 40D and 50D, I measured the noise as a function of spatial frequency for a midtone at ISO 1600 and found

They are the same at the same spatial frequency. However, the 50D has a higher Nyquist frequency, so the noise power spectrum extends further. The pixel level std deviation measures the area under the curve, and it is higher for the 50D because the spectrum extends further.

So noise at the same spatial scale is the same, noise at very fine scales is present on the 50D because the 50D has finer scales available than the 40D. The question is what is the visual impact of that extra noise power at fine scales. Well it's going to be similar to the visual impact of higher resolution -- if you can see the effect on resolution of the extra pixels of the 50D, then you're going to be able potentially to see more noise as well, but only at very fine scales. It should also be noted that interpolation errors are pushed off to finer scales, and are thus less objectionable, so there is somewhat of a compensating effect depending on how good the RAW converter is.

Now, what to do about it? One option is nothing, if the fine scale noise is not objectionable. Another is to apply a low pass filter, which is what downsampling does; this seems a bit silly, as it removes all image data beyond the cutoff of the low pass filter, both noise and image detail. Most sensible, if the noise is bothersome, is to use one of the better noise filters; that will dampen the high frequency noise while retaining much of the high frequency detail.

In short, don’t worry about pixel size or noise. Sensor technology
has matured to the point where there isn’t much difference in
performance between the various manufacturers. Just get the camera
with the features you desire.

Couldn't agree more.

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