Monday, January 11, 2010

11. Light Text, Dark Background

The Idea: Because most of the world's books present black text printed on white paper, most web pages do the same—people are accustomed to reading black on white and so it's become standard. Yet a paper page utilizes reflected light to produce an image that the eyes can see. Light shines on the page and bounces off the white part and that it what we're seeing. Meanwhile a computer monitor uses projected light aimed right at the retina. Though the irritable strength of this projected light is considerably lower in a modern flat-panel LCD than with an old-school cathode ray tube, any light-emitting monitor is projecting light directly at the eyes and this can be harmful to the vision. By reducing the amount of light beamed into the eyes, the retina is spared some of a computer screen's ill effects.

How To: Try using inverted text (a lighter color on a darker background) on your computer monitor. There are several ways to do this:
• On a Mac: Hold down the 3 keys next to the space bar (⌃⌥⌘ or Control-Option-Function) and the number 8. This will reverse black and white, as well as all colors, so you may need to toggle back and forth to look at photos and other images. This function can also be accessed in the Universal Access section of System Preferences.
• In Windows: Open the Control Panel in the Start menu and select Accessibility Options. Click on the Display tab and select the Use High Contrast check box. All text will appear as white on black and in bold. This might mess up the formatting of some web pages and certain programs, but is doesn't invert the colors on images. You can also adjust your computer's high contrast function by clicking the Settings button.
• Microsoft Word: Under the Word menu, select Preferences and click on the General Menu. Check the box that says "Blue background, white text" and hit OK. The document's text will appear as white on dark blue paper, but will print as black on whatever color paper you put in your printer.
• Using Google: Some folks have set up an inverted text search engine called Blackle, based on the notion that projecting so much white light uses an excess of energy. If excessive white light is straining the power grid, what's it doing to our eyes?

More Info:
• There are lots of arguments both for and against the use of inverted text. A web search leads to several forums full of users advocating black text on a white background, saying that inverted text hurts their eyes. These web forums are, of course, on sites using black text on a white background, so it is more likely for their users to be attracted to and argue for this format. Try using inverted text for a week and then see how your eyes feel.
Lighthouse International and the American Foundation for the Blind both advocate white or yellow text on a black background for older people and people with impaired sight.
• Other operating systems, programs and websites have options for inverting text (including the blog-hosting site that you're looking at right now). If you know of others, please post them as a comment below:


  1. Ive read about how the prevalence of high-contrast lighting in our culture is unhealthy for us. For example, its common to be temporarily blinded when we step into, say, a dark alley or room from a brightly-lit space, or vice versa, leaving us more likely to have an accident for those few moments, or more open to attack.

    I think I read about this phenomenon in the description for the winner of some sustainable design contest. The design team created light-sensitive street lamps that dimmed and brightened in response to the amount of light coming from the sky.

    In addition to using light text on a dark background, I'd like to try using low-contrast color schemes (I'll test-run it on my blog) for a while and see how that impacts my vision.

    Good stuff Morgan!

  2. Apple's iPhone also uses a light sensor to adjust the contrast on its screen—as do our eyes! Our pupils contract and expand to adjust for different amounts of light. To help adjust to different amounts of lighting, try Sunning—there's a reason why I made it the first entry on this blog.