MegaPixel (MP)

Pixel :

Dgital imaging, a pixel, pel, or picture element is a physical point in a raster image, or the smallest addressable element in an all pints addresable display; so it is the smallest controllable element of a picture represented on the screen. The address of a pixel corresponds to its physical coordinates. LCD pixels are manufactured in a two-dimensional grid, and are often represented using dots or squares, but CRT pixels correspond to their timing mechanisms and sweep rates.

Bits per pixel

The number of distinct colors that can be represented by a pixel depends on the number of bits per pixel (bpp). A 1 bpp image uses 1-bit for each pixel, so each pixel can be either on or off. Each additional bit doubles the number of colors available, so a 2 bpp image can have 4 colors, and a 3 bpp image can have 8 colors:

• 1 bpp, 2¹ = 2 colors (monochrome)
• 2 bpp, 2² = 4 colors
• 3 bpp, 2³ = 8 colors

...

• 8 bpp, 2⁸ = 256 colors
• 16 bpp, 2¹⁶ = 65,536 colors ("Highcolor" )
• 24 bpp, 2²⁴ = 16,777,216 colors ("Truecolor")

Megapixel

Digital cameras use photosensitive electronics, either charge-coupled device (CCD) or complementary metal–oxide–semiconductor (CMOS) image sensors, consisting of a large number of single sensor elements, each of which records a measured intensity level. In most digital cameras, the sensor array is covered with a patterned color filter mosaic having red, green, and blue regions in the Bayer filter arrangement, so that each sensor element can record the intensity of a single primary color of light. The camera interpolates the color information of neighboring sensor elements, through a process called demosaicing, to create the final image. These sensor elements are often called "pixels", even though they only record 1 channel (only red, or green, or blue) of the final color image. Thus, two of the three color channels for each sensor must be interpolated and a so-called N-megapixel camera that produces an N-megapixel image provides only one-third of the information that an image of the same size could get from a scanner. 

A camera with a full-frame image sensor, and a camera with an APS-C image sensor, may have the same pixel count (for example, 16 MP), but the full-frame camera may allow better dynamic range, less noise, and improved low-light shooting performance than an APS-C camera. This is because the full-frame camera has a larger image sensor than the APS-C camera, therefore more information can be captured per pixel. A full-frame camera that shoots photographs at 36 megapixels has roughly the same pixel size as an APS-C camera that shoots at 16 megapixels.

Thus, certain color contrasts may look fuzzier than others, depending on the allocation of the primary colors (green has twice as many elements as red or blue in the Bayer arrangement).A megapixel (MP) is one million pixels, and is a term used not only for the number of pixels in an image, but also to express the number of image sensor elements of digital cameras or the number of display elements of digital displays. For example, a camera that makes a 2048 × 1536 pixel image typically uses a few extra rows and columns of sensor elements and is commonly said to have "3.2 megapixels" or "3.4 megapixels", depending on whether the number reported is the "effective" or the "total" pixel count (as opposed to the 2048 × 1536 = 3,145,728 finished image pixels).