When shooting with a digital camera, it's important to know how many megapixels the sensor supports, because it can have a direct effect on image quality. Below, we've outlined how megapixels vary between camera models, how they affect sharpness, and why there is such a thing as "too many megapixels".
What are megapixels?
Simply put, a megapixel (often abbreviated as "MP") is one million pixels. When a camera boasts "12 MP", it means it can effectively produce images that contain 12 million pixels total. To capture visual information, digital cameras use special image sensors, which are either complementary metal-oxide-semiconductors (CMOS) or charge-coupled devices (CCD). Typically, these sensors have dedicated elements that record each primary color — red, green, and blue — which are then brought together to produce the final photo.
What about the camera lens?
Megapixels may represent how many pixels a camera can capture, but the lens plays a major role in image sharpness as well. When a camera manufacturer lists the megapixels of various models, this is only what the camera sensor can achieve, and it doesn't take the lens into account. To deal with this discrepancy, photographers often rely on the "Perceptual MegaPixel" (P-MPix), which is a ranking system that lists the resolution of different camera-lens combinations. Some lenses reduce a camera's MP more than others, so it helps to check the P-MPix for a more accurate measurement.
Do image sensors affect the megapixel count?
A camera may boast 22 MP, but the sensor makes a difference in how those pixels are captured. Larger sensors offer better performance in low-light conditions, produce more dynamic range (i.e. difference between light and dark areas), and reduce unwanted image noise. This heightened sensitivity produces cleaner and more accurate images, even if the pixel count is effectively the same.