Digital Camera Megapixels and Sensor Size
Some people believe that the path to a good photograph is a camera that has a sensor that can capture a huge amount of megapixels. This is only partially true. Not all megapixels are created equal. If you remember back in the dark ages when photographers used film, there were different film formats. Each film format designated the size of the negative.
Negative sizes ran the gamut from the miniscule 110 film, which was used in miniature cameras and had a negative about the size of your thumbnail, to large format cameras with negatives as large as 8 x 10 inches. When you start with a larger negative, you can create a larger print.
The same is true of digital cameras. The small point-and-shoot cameras (which can fit in your shirt pocket) have small sensors. Digital SLR cameras have larger sensors, full-frame dSLRs have even larger sensors, and medium-format digital cameras have even bigger sensors.
If you cram a lot of pixels onto a small sensor, and put the same number of pixels on a larger sensor, the pixels on the larger sensor are bigger. All other things equal, you end up with better image quality when you enlarge images captured with the camera that has the larger sensor.
When you have a camera with a smaller sensor, a lot of circuitry is confined to a very small space. As a result, the smaller sensor is likely to create more digital noise than you’d find on an image created with a camera with a bigger sensor. The increase in digital noise becomes more apparent when you increase the sensor’s sensitivity to light by increasing the ISO.
At low ISO settings, most point-and-shoot cameras yield acceptable pictures. When you take photographs in low-light situations at higher ISO ratings, though, digital noise becomes apparent, especially in the shadow areas of the image. The digital noise may not be noticeable in a 4 x 6 print of the image; when you create an 8 x 10 print of the same image, however, the digital noise will be visible.