questionscan somebody explain poor/good/better/best for…

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Generally the larger the sensor size, the less noise and better image you will get. Unfortunately, this sort of information isn't made much of except in DSLR's. I would stay away from 12MP pocket cameras - they're cramming too many pixels onto a sensor and you'll get noisy photos as a result. 6 or 8MP is plenty. I have a 12MP Nikon D300, and the RAW files for each photo are 10-13MB each! If they made it in a 6MP version with lower noise I would get it.

Canon has finally quit the megapixel race with in their G-series cameras and gone for quality over quantity. Hopefully other manufacturers will follow suit soon.

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I should mention that the D300 picture quality is very good in case I gave the wrong impression. DSLR's have larger sensors than pocket cameras and can handle more pixels without problems.

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There are two different types of sensors. CCD and CMOS.

CMOS will have less noise and can do higher ISO (how sensitive the senor is, usually is adjusted by the camera to the optimum level to balance getting the levels right and reducing the noise).

CCD is cheeper and can usually pack more of the sensors in but there will be more noise and less ISO.

8x10 prints...6 MP will be fine unless you are printing it on a really high end printer, even then only professionals and perfectionists can pick out the differences.

I own two cameras: Nikon D90 with a CMOS sensor at 12 MP I think (you can see how important that is to me). I agree that if they offered one with 8-10MP then i would have gotten that to reduce my noise and possibly increase the ISO.

I also have a Samsung NV7. My favorite camera ever! Only two problems with it are the size of the non removable lens and the noise at high ISO. This camera has won me awards!

If i were buying now? SLR with a CMOS sensor around 10MP.

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@frankandbeans: That's kind of misleading... the larger the pixel site, the more discreet levels of charge it can see, so the size relates to dynamic range. Smaller, more dense sensors are given to 'bloom' and blow-out, because the sites can only hold so much charge.

Noise in these kinds of systems has to do with rejection of spurious information, like stray charges from the circuits and random events that get recorded. Software in the cameras looks for what it considers noise (isolated pixels that are vastly different than the surrounding pixels). Since large sensors are more sensitive, they are more susceptible to true noise.

Where your observation is correct is in low-light situations, but again that has to do with the ability of the sensor to collect different levels of light, not how susceptible to noise they are. Smaller pixels need to stay active for longer to collect low-light, so lose discrimination.

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This came up randomly, so I figured I'd update it...

There are two different things being discussed: pixel size and sensor size. Pixel size is how big the little light collectors are, while sensor size reflects both the physical dimensions and how many pixels there are. A full-frame sensor may have 8MP, so relatively few pixels, which means the pixel sites can be bigger and more sensitive. The Nikon D800 has a 36MP sensor, with pretty small pixels, but the processor has gotten amazingly good.

That means the above discussion is not as relevant as it once was. Camera phones now routinely cross 6MP or larger in size, and still have decent performance. The wary consumer now should rely more on actual results than tech specs. Fortunately there are tons of review sites out there, so if it matters to you, wait for the products to get reviewed and check out the sample images on your own.