Pixel density revisited

Started Oct 22, 2008 | Discussions thread
OP igb Senior Member • Posts: 2,637
Re: Pixel quality vs Image Quality

John W Peterson wrote:

Thanks for your comments and insights. I'm guessing that you are an
engineer ? I am not, so any help is much appreciated.
I understand the point, which you made in your earlier posts about
the distinction between image quality and the pixel level
characteristic of S/N. These observations seemed correct /
non-controversial to me, which is why I didn't follow up on them.
My point, also I thought, not so controversial, was that sensor
design for any given manufacture improves over time, even though
there appear to be distinctions between the sensors produced by, e.g.
Canon vs Sony / Nikon. For that reason, comparing pixel density may
be useful primarily to help us think about differences between
differing cameras of the same generation. For example, canon has
introduced several digi-cams in the last year. Looking at pixel
density may help us to "pick the likely winners" amongst them as
regards pixel S/N.

In the event one is interested in pixel S/N instead of S/N of the final image.

As you raise the point of image quality, as opposed to pixel level
issues, let me just go after the dynamic range (DR) issue. You point
out that, for a given print size, the perception of image noise will
decline, as absolute pixel number increases. A simple way, that I
would look at it would be that the noise is lost in the sea of more
data. This however does not deal with the DR issue. If a given image
area, say, a white wedding dress, "pegs the needle" i.e blows out the
whites, then it won't matter how many pixels I have to record that
sea of perfect white. No increase in pixel number will make up for
that. What I need, are pixels with, individually, greater DR, and I
may need to put up with having much fewer pixels in order to get to
that. So, my conlusion is that although 'more and more pixels' might
help percieved noise, at a fixed print size, it won't help the DR
issue at all; in fact, it will hurt DR - unless some of those pixels
can be made to record at differing sensitivity levels (as with the
fuji sensor).
Comments ?

The pixel size and DR question has been discussed hereliterally dozens of times. Now I regret I didn't pay attention in any of them.

So much for my qualifications but instead of a comment let me pose you a question: for any given intensity of an evenly distributed 'rain of photons', which would fill earlier 10 pixels able to 'hold' 600 photons of 5 pixels able to hold 1200?

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