more pixels are better!

Started Dec 14, 2008 | Discussions thread
Graystar Veteran Member • Posts: 8,373
Re: more pixels are better!

Iforgetwhat8was4 wrote:

Let me take another shot at understanding...

For a given sensor size and given chunk of light (more or less base
ISO), the camera can fill its pixels with enough photons that it can
statistically supress noise. This allows a 12mp compact, in good
light, to produce a file that can be enlarged beyond a 6mp DSLR
without showing pixelization. (Other limitations of the small format
might separate the image quality, however.) This is the easiest way
for a compact to rival some of a DSLR's capacities, so the designers
are motivated to do so.

No, sorry...this is a strike. Given similar pixel technology, noise depends entirely on sensor size. Given the same framing, the small sensor image will have more noise than the large sensor image. It is possible that the image from the 12MP compact will have more detail. That's certainly a possibility in good light. But even with more detail, it will have more noise. Even if the detail is reduced to match the 6MP sensor, it will have more noise.

Smaller sensor = more noise. There's no way around it. This, along with some other reasons, is why compacts with small sensor can't rival DSLR images (and they really don't...really.)

Now, if you add more pixels, you cannot capture more information.
The noise increases with the number of pixels, and you end up
dividing up noise and signal without increasing the latter. The same
thing happens when you increase ISO (reduce the chunk of light - the
signal). So at higher ISO, the sensor is not optimized to that level
of light and binning isn't perfect, so you lose more than you would
with fewer Mp to begin with. (???)

Hmmm...not how I would put it. At higher ISO you take in less light. Less light causes the noise to be statistically greater. Since the image is darker, the signal/noise combo is amplified to get the correct exposure, but that's not making the noise any worse...the noise was worse in the capture. In any case. Binning and such won't help...if it did all large sensors would be doing it...but they don't...because it doesn't help.

Am I warm?-)

Certainly at least 98.6 F

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thw
cpw
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