Understanding Photoshop is a biweekly column that takes an in-depth look at how digital photographs are built and manipulated. It is a college-level course in plain english for free at Photofocus. To learn more see this article.
Before you open your first image in Adobe Photoshop, its very important that you understand how a digital image is built. Knowing how computers represent your digital image data is essential to your career. Being a technical person will not make you more creative, but it will make you faster and more confident. Lets take a quick look at what a working professional must understand.
When it comes to digital cameras, most photographers (and salespeople) seem obsessed with megapixels. Because everybody knows that having more pixels means better images (it doesn’t by the way). Whats lacking in all this hoopla is a clear understanding of what pixels are and just how many of them you need.
The more pixels you have, the more RAM you’ll need to open the images and the more hard drive space to store them all. So its in your best interest to understand some of the technology behind the images you want to capture, manipulate, output, and store.
In the beginning
Essentially, computers, cameras and video devices use pixels to express image information. Each pixel is a small square of light. The pixel is the smallest portion of an image that a computer is capable of displaying or printing. Too few pixels and an image will appear blocky because there is not enough detail to work with. Too many pixels and the computer or output device slows down because it has to process more information.
But where did the term pixel come from? Pixel is an abbreviation for picture element. The word was coined to describe the photographic elements of a television image. In 1969, writers for Variety magazine took pix (a 1932 abbreviation of pictures) and combined it with element to describe how TV signals came together. There are even earlier reports of Fred C. Billingsley coining the word at NASAs Jet Propulsion Laboratory in 1965. Although the exact origins of the word may be disputed, its meaning is not. The word pixel quickly caught on, first in the scientific communities in the 1970s and then in the computer-art industry in the mid 1980s.
So what are megapixels?
When you shop for a digital camera, you are bombarded with talk of megapixels. Consumers are often misled about what megapixels are and how many are needed. A megapixel is simply a unit of storage, whether internal or on a removable card. A megapixel is one million pixels and is a term commonly used to describe how much data a digital camera can capture. As with your car, just because your tank can hold more gallons of gas doesn’t mean its more fuel efficient or better than your friends car.
Digital cameras use card-based storage, like this Secure Digital card, to hold the captured pixels.
For example, the iPhone 6 can capture pictures at 3264 2448 pixels, it is referred to as having 8 megapixels (3264 2448 = 7,990,272 pixels).
If you were to print that picture on paper at 300 ppi (pixels per inch), it would roughly be a 11 8 print. Professional photographers may need more pixels than this, but a consumer may not. It all depends on how the pixels are meant to be displayed or printed.
The more pixels you capture, the larger the image is (both in disk space and potential print size). Consumer usage (such as email or inkjet prints) is less demanding than professional usage (such as billboards or magazines). Professionals need more megapixels than consumers; hence, high-end cameras cost more because they are targeted at people who make money by taking photos.
TIP: Don’t believe the megapixel myth
More megapixels do not guarantee a better picture. Instead of picking a camera solely on how many pixels it will capture, investigate cameras with better lenses or options that are important to you. If you are shooting for large-format output, you’ll need a larger megapixel-count camera, but if you’re shooting for personal use, consider how you output most of your pictures.