There is a very common myth when it comes to camera and there megapixel count. Most consumers believe that more the megapixel, better is the image. While some of it (megapixels) is of course necessary, it is entirely a different thing when users start demanding 16, 20 or even 22 megapixels! Probably for users such as these the Nikon D800 is the answer. But honestly, does a gigantic amount of megapixel is even at all necessary? Unfortunately however, more than 60% of the times an user approaches the camera store clerk with a question, it is usually about megapixels. How much of it is in a particular model invariably makes or breaks the deal. It is about time that some of the myths about megapixels are explained and may be broken!
What are pixels? – If you compare the sensor of a camera with a big plate with numerous cavities, then each cavity is a pixel. These pixels are light sensitive and capture a particular wave length of light among the three primary colors of red, blue and green. When all these light information is collated (also known as interpolation) we have an image. Of course the more pixels there are, the more detail the image has. A million of these pixels are what makes one megapixel.
If you compare an average computer monitor it is about 1000 pixels x 1000 pixels. That means if you have a 1 megapixel camera, it will be enough for capturing and sharing images on the Internet and enjoyed on the computer monitor. So the first answer whether 22 megapixels is necessary is NO. You don’t need a lot of megapixels for shooting reasonable sharable quality images. Even if you want standard 4” x 6” print, a 2 or 3 megapixel camera is more than enough.
However, megapixels do seem to matter when you want to print large sized pictures and or want to make a tight crop. Many times fashion photographers do not always get the right shot when they are taking a picture. As such during post processing the RAW frames they crop the image to ensure that the picture is perfect for publishing. More details is better in such cases as even with a tight crop the image never appears blurry and pixilated. Cameras like the Nikon D800/800E or the Canon EOS 5D Mark III with their extreme megapixel count are perfect as such for their requirements.
It appears as such that more megapixels do have an impact on the detail of the final image. But even before all you megapixel worshippers can jump in joy, I must add that more megapixels have to be taken together with the size of the sensor. The more megapixels you pack in a sensor, the smaller the size of each individual pixel will become. That evidently means less and less light capturing ability and more noise. So unless you have a large sensor size, such as a full frame one, increasing the megapixels will actually have a detrimental affect on the final picture quality.
Read more on Megapixel vs Print size