Question: I am going to buy myself a digital camera. I am a bit confused about “megapixels” and print dimensions. Can you explain? – Simon
Answer: Digital camera technology can be very difficult to understand, especially if you just want to take a picture. After all, film cameras are a point-and-click affair, in which you rely on a photo store to get the images out of the camera and onto paper.
Digital cameras let you do all your own “developing” using your printer. You don’t develop images from a digi-cam in the traditional sense, though.
Perhaps, if I go over the basics, this megapixel business will make sense. Digital cameras are sold based on the number of megapixels they produce.
So what’s a megapixel? Let’s start smaller. A pixel is a single dot in a graphic image, because images are made up of clusters of dots. It’s short for “picture element”. Mega means one million. Since a megapixel is a measurement of an area of an image, it consists of one million pixels or one thousand pixels vertically and one thousand pixels horizontally.
Imagine that you are in a plane flying over a snowy schoolyard filled with children. The children have colored hats on, so from above they each look like tiny dots of color, which is what a pixel is. If very talented teachers managed to get 1,000 rows of 1,000 children per row to stand very still, from above you’d see 1,000 x 1,000, or 1 million colored hats. If you coordinated the colors of the hats, the very well-behaved children would en masse look like a square image and you’d have a one megapixel of children.
One-megapixel digital cameras can take photos that have up to one million pixels in them. Two-megapixel cameras can snap images that have two million pixels in them and three-megapixel cameras can take pictures that have, you guessed it, three million pixels in them.
For simplicity’s sake, the digital camera makers round to the nearest million. You’ll see ratings like 1.3 megapixels or 2.1 megapixels, too, though. There are two ways to view an image. One is on the screen and one is on paper run through a printer. If you plan to view images on a computer screen, you can get away with using a lower resolution (meaning fewer megapixels) camera.
Here’s why: Screen resolution is typically 72 dpi. The dpi acronym is short for “dots per inch”. A dot in this context is the same as a pixel. So a digital camera image that is 640 by 480 pixels would appear to be approximately 8 x 6 inches in size on a screen. If you printed the same image out at 72 dpi on a printer it would appear very grainy. Normally, you’ll need a printer resolution of 300 dpi for a decent image on paper. If you look at your printer manual, you may find that your printer has a maximum resolution of 600 x 600 dpi or even better. So the higher the number of pixels, the better the image you are going to get.
The approximate rule of thumb is a one-megapixel camera will give you good quality 5 x 7 inch prints.
A two-megapixel camera will produce 11 x 14 inch prints and
a three-megapixel camera will produce 12 x 17 inch prints, assuming that you printer could handle that size of paper.
If you have a three-megapixel camera and don’t have a printer capable of 12×17, is it a waste? Not necessarily. You could snap a shot of a landscape, for example, and then – using photo software – trim (or “crop”) the image and get a great printout on 8 x10 inch paper.
One final note: Digital cameras have multiple settings so, for example, a three-megapixel camera can still take low-resolution images. These cameras normally come with large memory cards. The cards are used to store the images until they can be moved to a computer. So when taking low-resolution images with a high-resolution camera, you will be able to store lots of them before running out of storage memory.
Also, if you have a printer that can produce output at a resolution of 600 dpi, you’ll want a high-resolution camera to produce an image with as many pixels as possible so you can create a high-resolution print.
After all of this techno-babble, if you are still interested in purchasing a digital camera, here are a few places you can search online: