more pixels are better!

Started Dec 14, 2008 | Discussions thread
bobn2 Forum Pro • Posts: 72,009
Re: More pixels are not necessarily better...

DaSigmaGuy wrote:

Iforgetwhat8was4 wrote:

or are they?

Could someone try to give a clear but comprehensive explanation of
why more Mp doesn't improve IQ?

Given a fixed sensor size the camera with higher "resolution" will
produce a physically larger image than one with lower "resolution"
but one that is noisier and has reduced image quality, because
smaller photosites equal more noise, fact.

Brave man, wading into the discussion without bothering to read it, and offering a contentious (and wrong) view. OK then....

Statement 1, wrong. The file produced by a higher "resolution" camera is not physically larger. If by higher resolution you mean higher pixel count (they are not the same thing, since a camera could have higher resolution but a smaller sensor and thus have fewer pixels) then the physical size of the image is dictated only by the output medium. The file produced by the camera has no physical size, it is a collection of bits, which are immaterial.

Statement 2, wrong also - both because small pixels do not produce an image that is noisier and also because higher pixel count increases image quality, all else being equal.

I understand that more pixels means more noisy pixels, and i've seen
that in my own cameras.

Well then why do need to ask?

Fishing to catch chumps who'll make ill informed posts?

But should twice as many pixels give twice the dynamic range, simply
because you could sample two pixels for a value with twice the range
of a single pixel?

Completely the opposite. A single Bayer pixel is actually the
combined output of at least four adjacent photosites, often
more...Make the photosites smaller by increasing the "resolution" and
it just increases noise whilst allowing slightly more detail to be
captured (and I do mean slightly more) its normally at the expense of
pixel level image quality....There is no such thing as a free lunch.

Got that back to front. A single Bayer pixel is a single photosite, receptive to one of three light wavebands. There is no such thing as 'pixel level image quality' - a pixel cannot record an image, it can only record a single value (unless it's a Foveon pixel) to measure the light incident on its own area.

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