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Which is a better and usable Smart Phone or Tablet keyboard?

  1. White / light characters on Black / Dark keys on the keyboard layout.
  2. Black / Dark Grey text on the white / light grey colour keys layout.

From the usability and user experience point of view, which should be the less stressful and easy on the eyes and can have a better visibility in terms of contrast and day-time or night-time usage?

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    I think this will depend a lot on display technology. 1) AMOLED displays don't emit light from black pixels, LCD displays do, and 2) with black-on-white, you need thicker lines. If the display resolution is low, thick letters may be less recognizable, because you have to add too much whole pixels. But high dpi displays will not have this problem. And this is without taking eInk devices into account, which are a completely different matter. There are no phones with eInk yet, but in theory, there could be, so the question encompasses them in general.
    – Rumi P.
    Nov 19, 2013 at 13:18
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    @RumiP. 2) with black-on-white, you need thicker lines. You meant I think that the other round way.
    – Roger Attrill
    Nov 19, 2013 at 14:21
  • @RogerAttrill good catch, thank you. Concentration sometimes makes me mix up the names of concepts I am talking about :(
    – Rumi P.
    Nov 19, 2013 at 14:47

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Within the context of the keyboard only (ignoring the rest of the screen) - it (nearly) doesn't matter.

On Contrast

Since it's grayscale you are talking about (luminance) most colour theory goes out of the window. The contrast between white and black is exactly the same as that between black and white (or any other two grayscale colours for that matter). This would not be the case if colours were involved since the smaller the colour patch the more important luminance becomes.

If there are more than 2 grayscale colours on the keyboard, read a bit on Luminance Nonlinearity.

Days and Nights

As far as night/day differences, more white means more brightness, which means a narrower pupil. In dark settings, often once you look away from a bright display, it takes a few seconds for the pupil to adjust its width to the low-light environment. In day light, the pupil width is little determined by the display brightness, since there are plenty of photons emitted from the environment.

To support night (low-light) interaction better, a darker interface would be beneficial.

In addition, you may wish to base your decision on other colours/grayscale on screen.

Reference: Visual Thinking for Design (Ware, 2008); Chapter 4 (Colors).

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(I will refer White-on-Black as WOB, and Black-on-White as BOW for brevity's sake.)

Answer to this question is not something one-liner.

It heavily depends on multiple factors. The major concerns are

  • the user himself, i.e. his own preference,
  • time of usage, e.g. WOB is easier in daylight, whereas that just hurts eyes when only the monitor is emitting light at mid-night.
  • location of usage, e.g. BOW is a nightmare for using outdoors
  • user's age,
  • the application of the usage. e.g. office-mail will differ than Instagram per se.
  • the device, e.g. Kindle may differ from 27" iMac etc.

The safe bet is to stick with black-on-white for it legacy similarity with ink-on-paper, regardless it is technologically, ergonomically, better or not.

However, that might not be the best bet for your majority users.

You can also check some deep analysis here: http://uxmovement.com/content/when-to-use-white-text-on-a-dark-background/

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Another reason supporting black on white is that even when performance is equivalent, users often perceive pages with darker backgrounds as loading slower.

I have seen this is user studies I have run, and here are some papers and articles which explore color and perceived load time. These address some specific colors, not just dark/light, but it establishes the concept:

http://www.itdinteractive.com/2013/web-design-tips-use-red-for-slow-load-times/

http://journals.ama.org/doi/abs/10.1509/jmkr.41.2.215.28668?journalCode=jmkr

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  • Do you have any research or references to qualify your answer?
    – Charles Wesley
    Nov 22, 2013 at 17:37
  • These are good research papers Kassy. Very helpful. Thanks!
    – Justin Samuel
    Mar 28, 2014 at 4:30

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