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In our office we have transparent glass doors and we want to put text stickers on them. For example, name of the person or room function.
The question is what color should be stickers to provide optimal readability? We are deciding between black or white, but maybe there's a better solution?
There is a better solution, at least in terms of legibility, perhaps not so much aesthetically. And I'm 99% sure you've already seen it.
Black border, white letters.
White letters are almost always brighter than the background, and the black outlines act as a sort of shadow, separating the text from the background.
Of course, the best legibility is still achieved by controlling the background; so adding a flat colour backdrop.
Both of these solutions, however, require the use of 2 colors, so this might not be the answer you're looking for, due to it being more complex and likely more expensive.
Years ago I worked at a sign shop doing vinyl lettering. White.
Black might get hard to read as shadows cast (including walking by the door). Unless the background is light enough to guarantee, I think white is your best option.
There's no one-size-fits-all answer. The answer might depend on the reflectiveness of the door, how dark the room behind it is, and even the position of the lights. To determine what's appropriate for your environment, try the following quick experiment.
Take a picture of the door from roughly where someone might stand to read the sign. Blur the picture a little, and sample the color of several pixels roughly near where the sign would be posted to get their hex codes. Then use a contrast checker such as this one. Contrast the sampled pixels' hex codes with both black (#000000) and with white (#FFFFFF). Select the variation that give the higher contrast ratios.
WCAG guidelines suggest a minimum contrast ratio of at least 4.5:1. If you're not reliably getting that for all of the sampled pixels in your chosen variation, it's probably an indication that the contrast is too low and that a sign on the door will not be sufficiently readable. (If that's the case, consider giving the text a background or placing the sign somewhere else.)
I think Pixel's answer makes sense on displays, but wouldn't look so great in the physical world. It sure is "optimal for readability", but I think the aesthetics are a factor to consider, in the physical world.
An important difference between superimposed text on an image and text on glass is the ability to change the background. On physical glass, not only does vision with two eyes allow you to better pick out the text, you can even physically move to make the background move in perspective. Physical-world shadows and off-white colors will also make color differences a little more evident. With white text on white pixels, there's not a lot of room for error.
As a watcher of TV series House MD and Suits, I was reminded of their fancy names on their office doors:
While not maximally optimally readable, I'd advance white text is at the intersection of reasonably readable and good-looking.
#fff vs #ddd in that context, etc.
Mar 22, 2016 at 13:21
In a building I perform security for, there are a number of doors/offices/whatnot that have identifiers that are [solid color] on top of a metallic semi-reflective layer. This representation is both classy and provides clear readability to those looking at the identifier. The background auto-adapting to the lighting conditions is a secondary plus.
In general, white or yellow on semi-reflective may be more visible/readable than black on semi-reflective since even in high illumination environments, there will be plenty of semi-dark (not-quite-bright) that the semi-reflective will render as darker than the white/yellow.
