Why are pixels important? What are megapixels? A megapixel, often abbreviated as MP, is 1 million pixels. A pixel is a single element of a digital image. The number of megapixels determines the resolution of an image and a digital image with more megapixels has a higher resolution. A higher resolution is certainly desirable in digital photography, as it means that the camera uses more pixels to create the image, which should allow for greater accuracy.
The technical aspects of megapixels
On a digital camera, the image sensor records the photograph. An image sensor is a chip that measures the amount of light that passes through the lens and hits the chip.
Image sensors contain tiny receptors, called pixels. Each of these receptors can measure the light that hits the chip, recording the intensity of the light. An image sensor contains millions of these receptors and the number of receptors (or pixels) determines the number of megapixels that the camera can record, also called resolution amounts.
Don't mess with the Megapixels
This is where things get a little complicated. While it is obvious that a camera with 30 megapixels should produce better image quality than a camera that records 20 megapixels, this is not always the case. The physical size of the image sensor plays a more significant role in determining the image quality of a particular camera.
Think of it this way. A larger image sensor with physical dimensions that contains 20 MPs will have larger individual light receptors on it, while a larger image sensor with physical dimensions containing 30 MP will have very small individual light receptors.
A larger light receptor, or pixel, will be able to more accurately measure the light entering the lens from the scene than a smaller light receptor. Due to inaccuracies in the measurement of light with a small pixel, you will get more errors in the measurements, resulting in "noise" in the image.
The disturbances are pixels that do not seem to be the correct color in the photograph.
When the individual pixels are closer together, as they are with a small image sensor, it is possible that the electrical signals generated by the pixels may interfere with each other, causing errors in the measurement of light.
Therefore, while the number of megapixels a camera can record has a role in image quality, the physical size of the image sensor has a greater role. For example, the Nikon D810 has a resolution of 36 megapixels, but it also offers a very large image sensor, so it has the best of both worlds.
Changing the MP settings
Most digital cameras offer the ability to change the number of megapixels recorded for a particular photo. So if the maximum resolution of the camera is 20MP, you may be able to record images that are 12MP, 8MP, 6MP, and 0.3MP.
Although it is generally not advisable to record photos with fewer megapixels if you want to ensure a digital photo that will require a limited amount of storage, you shoot with a lower megapixel setting, such as recording with a larger number of megapixels or higher resolution requires more storage space.