Are there any reasons to avoid using white text on a black background?
Here's an article on it. To quote the article's quotes:
However, most studies have shown that dark characters on a light background are superior to light characters on a dark background (when the refresh rate is fairly high). For example, Bauer and Cavonius (1980) found that participants were 26% more accurate in reading text when they read it with dark characters on a light background.
People with astigmatism (aproximately 50% of the population) find it harder to read white text on black than black text on white. Part of this has to do with light levels: with a bright display (white background) the iris closes a bit more, decreasing the effect of the "deformed" lens; with a dark display (black background) the iris opens to receive more light and the deformation of the lens creates a much fuzzier focus at the eye.
If you do want to use a dark theme, see how others use it:
- Gray on black
- Large font
- Eggshell on gray
- ClearType (zoomed out on an LCD, the text looks yellow-white; you don't notice the blue)
Timothy Samara in Design Elements: A Graphic Style Manual provides interpretation of the colors black and white. Samara tells us that the color black is "extreme [...] the strongest color in the visible spectrum." He further calls it dominant and also typical of the feeling of nothingness. The color white, on the other hand we know is "all" colors, that feeling of wholeness and clarity.
A dominant darker-value color region (the black field) will cause our brain to expand lighter-value colors placed within it. The effect is that lighter-value objects will tend to bleed into the void of the very dark-value region. Practically, white characters will look heavier in a dark background.
Letters require a certain amount of space between each other to be readable—they need to be close enough to look like a grouped collection (and look like a word) but not so close that the boundary between letters becomes indistinct (and makes the group look like a blob). As the letters look thicker, the apparent space between them decreases and words tend toward bright white blobs. Unless the font presentation is modified, this makes white-on-black less readable and therefore undesirable.
White-on-black can be achieved, however, with a little extra effort in the interface's style sheets (or whatever is used to define how/what text is presented).
- First, a "thin" or "light" (not "narrow") font or font-weight will reduce the effect of the letter body bleed. Alternatively, a larger type size will provide the letter glyphs with enough surface area to successfully battle the black background for visual dominance.
- Secondly, an increase in letter spacing (more-so for the smaller font sizes) will give the glyphs the bit of extra room they need to look like letters. These two effects can mitigate the usability losses of standard fonts in white on a black background, allowing you to use said alternative color combination.
It's mostly about the contrast and the medium. If the contrast is too high than glowing letters on a dark background may strain the eye.
Here is an interesting conversation on the subject with lots of thoughts.
A few points:
The eyes' iris' adjust to according to the amount of light the eyes receive. If most of the area is black and then you have a very bright light it can strain the eyes, therefore if the screen has a strong intensity level gray on black is more recommended than white on black, however, the intensity level of screens can be adjusted so this is less of an issue.
As Matt quoted, in our perception of the images we view, bright areas expand to darker areas, thus regular text seems more bold when the text is brighter than the background. If the text is bold to start with, the result of white on black may seem too bold, however, for regular text, I find that the text seems to "stand out" more and is easier to read.
If I am not mistaken, most text is not bold, therefore it makes more sense to optimize the viewing of regular text that that of bold text.
If you are reading in a dark environment, then a white background will strain the eyes when ever you look away from the screen or back at it.
If you are reading in a bright environment, then refer to this answer.
If you are reading formatted text with many colors/shades (e.g. reading/writing code) or working with images then darker colors on a black background will be easier to perceive than brighter colors on a white background (see formula for contrast here).
It is a common (mis)conception that white backgrounds are preferable, however, those I know that have really tried working with modern screens and dark backgrounds with suitable foreground colors prefer it.
As Fraser pointed out, the studies quoted are outdated and not enough factors were measured (e.g. period of time in front of screen, screen type, room lighting, diversity of text shades and colors).
Cleartype is used on modern LCDs (new "LED" screens are really LCDs too, just with LED backlight instead of florescent) for white on black and for black on white. It is a method of anti-aliasing by using sub-pixels and has nothing to do with which is darker.
While it has since been fixed, there was a time when Safari (the default browser on Mac OS X) antialiased light text on black very differently than dark text on white, making it look too bold (which looked especially bad on very bold text tracked tightly).