1.What is Megapixel/MP
A “Megapixel” is a short form of Million Pixels. 1 Megapixel is equal to 1 million pixels. That means a 1-megapixel camera contains 1 million pixels on his sensor. It is used to define the resolution of a digital camera camera. If a camera has, say, 20 megapixels, there are 20 million pixels in the sensor. Also the maximum resolution of the images the camera produces is 20 megapixels. However, because there is complex calculation done to the image including correction of geometric distortions these pixels do not go one to one. Unlike say in TV where each pixel has three colors sub pixels, in a digital camera sensor each pixel senses only one color component. Typically half of the pixels sense green, a quarter each for blue and red. To create all components to each pixel the neighboring pixels are used. Then the mage is, especially on fixed lens cameras, corrected for geometric errors as it is easier to make a lens that produces distortions and correct them than to make a distortion free lens. It is also subjected too much other correction like noise reduction. Cameras even can mask bad pixels away so that they will not show.