Cellphones with high megapixel cameras allow photographers to print larger photos and crop images without noticing a loss of quality. While computers monitors often only need between 1 and 3 megapixels for optimal appearance, a 14-by-11-inch printed photo requires at least a 7-megapixel image to look its best, or higher if the image needs cropping. Since megapixels are only one facet in determining a camera's overall quality, some lower megapixel cameras can also produce pictures with excellent quality.
When a camera produces a high megapixel image, the quality of the image can suffer if the sensor is too small or a low quality. This occurs because each pixel space is smaller and captures less light. As a result, off-color pixels from electronic noise appear on the image because the sensor compensates by becoming more sensitive to light. A camera with high-quality image processing capabilities can mitigate this problem to a degree.
A megapixel is a measurement in which each unit is 1 million pixels, which are the square dots that comprise a digital image. A 5-megapixel camera produces images containing 5 million pixels. The megapixels of an image are calculated by multiplying its dimensions. For example, a 2000-by-1000-pixel image is exactly two megapixels.