Why light text on dark background is a bad idea
As this is a suggestion which comes up quite regularly, I felt it valuable to document some of the research I have collected about the readability of light text on dark backgrounds.
The science of readability is by no means new, and some of the best research comes from advertising works in the early 80s. This information is still relevant today.
First up is this quote from a paper titled “Improving the legibility of visual display units through contrast reversal”. In present time we think of contrast reversal meaning black-on-white, but remember this paper is from 1980 when VDUs (monitors) where green-on-black. This paper formed part of the research that drove the push for this to change to the screen formats we use today.
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.
Reference: Bauer, D., & Cavonius, C., R. (1980). Improving the legibility of visual display units through contrast reversal. In E. Grandjean, E. Vigliani (Eds.), Ergonomic Aspects of Visual Display Terminals (pp. 137-142). London: Taylor & Francis
Ok, 26% improvement – but why?
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.
Jason Harrison – Post Doctoral Fellow, Imager Lab Manager – Sensory Perception and Interaction Research Group, University of British Columbia
The "fuzzing” effect that Jason refers to is known as halation.
It might feel strange pushing your primary design goals based on the vision impaired, but when 50% of the population of have this “impairment” it’s actually closer to being the norm than an impairment.
The web is rife with research on the topic, but I think these two quotes provide a succinct justification for why light text on a dark background is a bad idea.
(Tip: If you want to be really good, use an offset grey on a light background like #222 on #fff as it’s a bit nicer on the eyes.)
Hi,
I haven’t read any papers on this topic, but one thing that I know is that the reason for people to try and switch to white on black is the fact that the eyes get really tired by looking for 12+ hours at the white screen.
So, the arguments you give here are may be relevant for short term, but what those articles say about long use?
vvvlad
October 14, 2008 at 08:30
Black print on a slightly yellow background (see my blogsite) is very readable AND helps on the tired-eyes issue.
BTW: Follow-Me trucks at airports are black and yellow form aximum visibility.
Ole Phat Stu
October 15, 2008 at 03:54
Agreed with previous responses. As a developer with very bad astigmatism and keratoconus, I notice that I am only good with dark text on white background for about 4 hours before my eyes hurt.
I can code with bright colors on black screen all day without my eyes hurting.
Maybe the having only one forecolor has a detriment not noticed when multiple colors are used say with Netbeans editor?
Michael F
October 16, 2008 at 02:03
An interesting angle. One question I have: assuming it’s true that nearly 50% of the population has astigmatism, wouldn’t many (most) of them have corrected it? I’ve seen an estimate that 25% of American adults are myopic to at least -1.00 diopters; does that mean “make the letters bigger?”
References cited in the Wikipedia article on astigmatism suggest a prevelance closer to 30%. One of those references points out that refractive errors, including astigmatism, vary significantly among children in four ethnic groups, even controlling for age and sex.
Dave Ferguson
October 16, 2008 at 05:25
Yeah, I use light on dark as well. Although, regardless of the light on dark or dark on light, I never use full black or full white.
I’ll typically use a light gray and a very dark grey, as I find it a little easier on the eyes.
Alex
October 16, 2008 at 05:44
[...] were hard to read. Apparently not being able to read light text on a dark background is due do to astigmatism. This was one drawback of bad eyes I have never heard of. Since all four contestants had the [...]
And the winner is « Bajook's Blog
October 18, 2009 at 01:33
As a CAD operator, light colors on a black background is a de-facto standard. It’s better for seeing details for longer periods of time with minimal eye fatigue.
Which strikes me curious that MS has all but eliminated the ability to accomplish this in any of their software. See for yourself by setting your windows colors to make this occur by default – menus, text fields, title bars, and other items that should coordinate with your settings don’t, they want to be black on white, and therefore become the same color for both.
Thank you MS for not getting the user base.
Vince
December 11, 2009 at 09:21