Digital photography represents nothing less than a revolution in the way we take and manipulate images. Even so, the basic fundamentals of film photography apply with digital. Both require a lens to focus light and a shutter to let that light pass into the camera. The principal difference between digital and film photography is how the image is captured.
Traditionally, you needed to have your film developed in a darkroom using various chemicals (none of which were very environmentally friendly). The process of developing the film produces “negatives” that needed to be further processed and printed before any usable image was produced. Needless to say, the moment that the shutter was originally snapped is long gone by the time you actually see the product of your image making. With digital, the image is captured using an electronic sensor. This sensor is made up of millions of individual “pixels”, or picture elements, that convert light into a zero or one (binary code). Thus, instead of waiting days or weeks (at best, hours) to see your image, with a digital camera, you see it almost instantaneously.
The quality of the image with a digital camera depends in large part to the number of pixels it has. This is commonly referred to as the “resolution” of the digital camera, and can be expressed as a dimension (800 x 600), or the number of pixels per inch. 800 x 600 is a common resolution for computer screens. A screen with this resolution will display 800 pixels from side to side, and 600 from top to bottom, totaling 480,000 pixels. Modern digital photography normally uses a much higher resolution than your average computer screen, going up into the millions of pixels, or megapixels. Thus, a camera with a resolution of 2048 x 1536 represents 3.1 megapixels.
We know that each pixel is represented by a number. The color scale of that pixel is determined by the size of the number. Black and white images can be produced by pixels a mere 8 bits in length. A quick refresher in binary arithmetic tells us that an 8 bit number represents a decimal number between 0 and 256. Therefore, and black and white image can have 255 shades of gray, plus black, 0, and white, 256.
For color, we need more bits. At 16 bits per pixel, we can have a color scale with 65,536 different shades. 24 bits brings that into the millions. Most digital cameras nowadays use 24 bits, with some professional equipment utilizing all of 48 bits for a whopping 280 billion shades. That’s a lot of color!
Several factors affect the quality of a digital camera. Pixel resolution is normally considered the most important one. To choose and adequate pixel resolution, you should take into consideration the size of images you wish to print – or if you are going to print your images at all. The number of pixels in an image doesn’t change, so larger images will have fewer pixels per inch, resulting in a loss of detail that will continually degrade the larger the picture gets.
Most photo labs print images at 300 pixels per inch. Use this as a base to calculate the megapixel resolution for your digital camera. A two megapixel camera at 300 pixels per inch will produce a maximum print size of 5.8″ x 3.8″, less than the standard 4″x8″. Considering a four megapixel camera will produce a print, at 300 pixels per inch, of 8.2′ x 5.4″.
There is nothing stopping you from printing larger pictures, of course. These are just guidelines. A 200-pixel-per-inch image isn’t as sharp as the standard 300 pixels per inch, but for many purposes can still be quite acceptable. At this resolution, you can bet images up to 8.7″ x 5.8″ with a two megapixel camera, all the way up to a 12.2″ x 8.2″ image from a four megapixel camera.
Now that we have pixels and megapixels swimming in your head, it’s time to step back and just enjoy all the advantages offered by modern digital photography.