OS X Yosemite public beta enables an intriguing feature referred to as Dark Mode. No one is quite sure why it's there, but it's very cool.
From the dawn of Mac time, menus have been black text on a white background. Perhaps, at some point, Jony Ive asked: "Why must that be so?" And so, behold, we have Dark Mode.
Dark Mode consists of:
- Turning the menu bar black
- Turning the menu background to a dark gray with white text
- Darkening the background of the dock.
In my reading, I can't find anyone who knows for sure why this feature exists. I doubt if it's for energy savings because the LCD's LED backlight is always on, and it takes a bit of extra energy to block that light and turn pixels black. Even so, the difference in energy between a black pixel and a white one isn't dramatic. You can read more about that at Scientific American and Techlogg .
Dark Mode affects several areas of the Yosemite display.
My own theory is that the feature isn't to conserve energy but, rather, a feature designed to reduce the amount of light striking our eyes from those areas in very low light conditions — such as an airliner on a night flight with cabin lights dimmed — when turning down the whole screen brightness just doesn't do the trick or isn't visually pleasing. I could be wrong. [UPDATE: I have been told that it's for photographic work.]
Trek Into Dark Mode
Turning Dark Mode is easy. In Yosemite, go to System Preferences > General and check the box for "Use dark menu bar and Dock." The effect takes place immediately.
Sytem Preferences > General
While there's no guarantee that that this feature will survive to the final OS X Yosemite 10.10 release, the prognosis looks good. Previous betas enabled this feature, and only problematically, on the Unix command line. So it's a good bet that the current, more pleasing operation, which now works great, is here to stay.