WHAT IS A MEGAPIXEL?
First, let’s look at what a megapixel actually is. Every image you see on a digital photograph is made up of tiny dots, each one called a pixel. A megapixel is a term for one million of these pixels, and megapixel is used to describe the resolution of a digital image, as well as the resolution of a digital image sensor.
For example, when a JPEG image has a resolution of 4000 x 3000, it means that the image is made up of 4000 columns by 3000 rows of pixels. It has a total of 12,000,000 (4000 x 3000) pixels, and since that’s a rather large number to say, we shorten it by describing it as a 12MP (12,000,000 divided by a million) picture.
Megapixel is also used to describe the total number of pixels on an image sensor. To create a 12MP image, an image sensor has at least 12 million pixels, or photosites, on it. Each photo site captures light as it passes through the camera’s lens and hits the sensor, and translates that into digital information which is rendered into
an image by the camera’s image processor.
The total number of ective pixels is diferent from the total number of pixels on a sensor. An image sensor can’t use every pixel on it for the simple reason that a sensor is rectangular and lenses are round. So there are always pixels falling outside of the lens’ coverage, and the e ective pixels are the actual number of pixels which remain to capture the light.
Every digital photo is made up of little pixels.