When considering the purchase of a digital camera, you’ll notice that a great deal of emphasis is placed on how many megapixels a particular camera can capture. Why are megapixels so important? What do they mean to you? Are all cameras rated a given number of megapixels equal? How many megapixels do you really need? This article will tell you what you need to know. Let’s get started.
Pixels
Let’s begin with pixels. What are they? Pixel is a shortened form of picture element, meaning one individual spot of color in your picture. Digital images are made up of hundreds, thousands or millions of pixels.
Megapixels
How many pixels are in a Megapixel, then? One million. Let’s say you have a rectangular image 3000 pixels high and 4000 pixels wide. 3000 X 4000 = 12,000,000 pixels or 12 Megapixels. Simple enough, right?
So What?
But what difference does it make how many Megapixels a camera can capture? The size of your digital image affects quality, printing, and cropping.
Quality
The relationship between the number of pixels in your image and its quality is pretty straightforward. The more pixels, the better the quality of your image. Why? There’s more information in the image! If I take a picture of the same object with a 1.2 Megapixel camera and a 12 Megapixel camera, the 12 Megapixel image with have ten times more information about the object, because there are ten times as many pixels. That’s ten times as many spots of color, making a sharper, denser image.
Printing
The relationship of megapixels to printing is defined by PPI, or Pixels Per Inch. The printing standard used by magazines and professional printers is 300 PPI. That means they will not print an image with lower resolution. To understand how this relates to a given image size, let’s use our 12 Megapixel, 3000 X 4000 pixel image as an example. To determine the maximum print size, divide each of the dimensions of your image by the desired PPI, in this case 300. For our example image, this means the largest professional quality print that can be made is 10″ X 13.33″. You can choose a smaller PPI when making a print on your own, but the quality will begin to suffer when you do. As you reduce the PPI, the image will appear less sharp, and if you go low enough you’ll actually begin to see the square pixels in the print.
Cropping
Cropping is the practice of choosing some portion of your image to use for printing or viewing. This portion will have fewer pixels, and so is reduced in quality and potential print size. Let’s return to our 12 megapixel, 3000 X 4000 image. If you select an area that’s just 1200 x 1600, then the biggest professional quality print you can make is 4″ X 5.33″. If you started with a 24MP, 6000 x 8000 image, the same area of the image would be 2400 x 3200, allowing you to make a print of 8″ x 10.66″.
So, More Megapixels are Better, right?
Not always. There are a lot of variables that contribute to the image quality that a given camera will produce, and the number of megapixels the sensor can record is only one of them. The size of the sensor, the quality of the lens, and the software built into the camera all have an effect on image quality.
Then How Many Megapixels do I Need?
The right choice of megapixel capacity in a camera depends on what you do with your pictures. If you aren’t prone to extreme cropping and you primarily post your pictures online or make prints 8″ X 10″ or smaller, then anything over 8 megapixels is likely to be just fine. If you’re a heavy cropper or like to make big prints, go big on the megapixels. Fixed lens cameras are available up to about 16 megapixels these days. Interchangeable lens models are available up to 24 megapixels or so. When you get to those extremes, though, be prepared for some sticker shock, as you can spend thousands of dollars on the camera alone.
Summary
Megapixels are a useful measure of the amount of information a digital camera captures. The number of megapixels a camera can capture has a direct relationship to the size of the professional quality prints you can produce and the amount of cropping you can do with a particular image. Consider your needs and habits carefully when determining how many megapixels you need. Lastly, remember that megapixels are only one part of image quality. Rely on reviews and sample images to guide your selection, not just megapixels.