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Do megapixels matter with modern sensor technology?

Mobile phone manufactures now advertise their phones having camera with bigger megapixel count. Does it mean the quality of the pictures increase with the MP? Recently Nokia released a phone with 41 MP. That is really a big amount.
I read some articles and I came across the term absolute resolution. How can I know the absolute resolution for a camera?
Thanks.

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A bigger pixel count gives you a higher resolution image, which - all other things being equal - should lead to a better quality image. You'll be able to see finer detail as there are more blocks for the image to be broken down into. This will also allow you to print the image at a larger size without seeing the pixels.

However, with camera phones the limiting factors will probably be the quality (or otherwise) of the lens and the size of the sensor.

Once you reach the quality limits of the lens it won't matter whether the image is 30, 40 or 50 megapixels the image will look the same.

A smaller sensor will generate noisier images the the equivalent sensor on a DSLR. This will also limit (probably more so) the quality of the image.

Camera manufacturers have latched onto the raw megapixel number as an easy way of comparing cameras that looks like it should measure quality but it's not as simple as they are trying to make out.

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  • From your post what I understand is quality of the lens is a striking factor when it comes to devices like camera phones. Say there are two camera phone devices, one with Carl-Zeiss lens but with 5MP, other device with just a generic lens but with 10 MP. Since the lens from Carl-Zeiss are of better quality the first device will produce better image, right? – user2112 Jul 10 '12 at 12:28
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    @kadaj - possibly :) I won't say a definite "yes" for your example as the numbers might mean that the generic lens does produce a better image at 10MP than the Carl-Zeiss at 5MP, but essentially you're right. – ChrisF Jul 10 '12 at 12:31
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    There's also noise to consider. The more pixels crammed onto a sensor, the more noise you get. This is why point and shoot cameras are generally noisier than DSLRs, because people (erroneously) think more MP = better images, and so the manufacturers cram stupid amounts of MP onto tiny sensors for consumer cameras. The result: 98% of Facebook. – ElendilTheTall Jul 10 '12 at 12:56
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    Don't forget: smaller sensors are also diffraction limited at wider apertures. Once you reach a certain megapixel size, diffraction becomes visible even when the lens is wide open. Once you reach that point, adding megapixels only serves to make diffraction more obvious. Additionally, this means small sensors basically can't do macro (either DOF will be too shallow, or diffraction blur will be too severe - at least without focus stacking). – D Coetzee Jul 10 '12 at 20:48
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    @DerrickCoetzee: Keep in mind, while diffraction limitation occurs sooner, the SIZE of an airy disc is smaller than with a lower resolution sensor. If you have a 20mp sensor and a 40mp sensor, sure, the 40mp sensor is going to hit its DLA sooner, but your still resolving a hell of a lot more detail than the 20mp sensor. Many people think that once diffraction occurs, it degrades IQ BELOW that of a lower-density sensor...that is incorrect. Diffraction simply limits your maximum resolution...it will never reduce IQ below that of a less-capable sensor. Below the DLA, you just aren't gaining much. – jrista Jul 11 '12 at 3:21