Does "black" really save electricity?

[RESmonkey]

If I make my desktop background solid black, will I be conserving any power at all (even a tiny bit?)?

Does it matter if it is a CRT or LCD? I know it's something to do with electrons and energy levels.


Thanks

 

[xanis]

http://blogs.wsj.com/numbersgu...-save-electricity-104/

Basically, unless you're using an older CRT monitor, there really aren't any noticeable energy savings from using black versus colors.

 

[PolymerTim]

Makes sense it wouldn't effect LCD screens very much. You basically have a backlight that is always on full power and liquid crystals that change orientation to selectively block the light. I would guess that most of the power goes to the backlight.

 

[Eeezee]

I think on a CRT you may save a tiny bit.

The best reason to use a dark background is because it reduces eye strain. Why would you stare at a bright light? Also, the colors in vim are a lot cooler if the background is dark

 

[CTho9305]

Originally posted by: Eeezee
The best reason to use a dark background is because it reduces eye strain. Why would you stare at a bright light? Also, the colors in vim are a lot cooler if the background is dark

I've read that a white background is better because your pupils constrict, increasing the depth of field, making it easier to focus. Of course, you need a light behind the monitor - staring into a white light with darkness around is definitely bad in terms of eye strain.

 

[QuixoticOne]

It certainly saves power on CRTs and possibly on some kinds of flat panels like OLED displays or whatever.

It certainly saves one's eyes too, IMHO. I can't stand office applications, text editors, and PDF documents et. al that display black text on glaring white backgrounds. I always hack it so it does something like black on grey or blue on green or something less bright / contrasty.

It is annoying that so many of the web pages out there feel some kind of irresistible compulsive misguided need to override the browser based display formatting with their own fonts / colors / backgrounds / text sizes / image sizes. I'd be a lot happier picking my own fonts, colors, formatting, et. al. A lot of stuff just comes off unreadable and a is big waste of power / processing.

Keeping things darker is also nice if you're doing something like watching a video in one window and browsing in another.

 

[CycloWizard]

Originally posted by: CTho9305
I've read that a white background is better because your pupils constrict, increasing the depth of field, making it easier to focus. Of course, you need a light behind the monitor - staring into a white light with darkness around is definitely bad in terms of eye strain.

Your eyes are designed to see light things on dark backgrounds. This was proven by HK Hartline back in the 1960's using horseshoe crabs, which actually have compound eyes. Hartline won the Nobel Prize for medicine for his demonstration of neural inhibition, which causes the retina to essentially find edges on the fly. It does this by suppressing neural signals from cells adjacent to cells which are picking up higher intensities. So, if I have a black line on a white background, the border of the black line will appear gray. If I have white letters on a black background, the edges will become more clear and well-defined. If you consider color, the optimal design is a blue background with white or yellow text, which is what I use for all presentations and research posters.

 

[CP5670]

I have always used a Windows color scheme with bright green text on a black background. I find that much easier on the eyes, especially in a dimly lit room. However, the difference in power usage on a CRT is only about 15W (at least that's what I measured with mine), and there shouldn't be any difference at all on LCDs.

The only annoying aspect of these colors is that certain programs and websites aren't designed to work with them and keep the text black, so you get unreadable black text on a black background. These are rare enough though that I just put up with them.

 

[CTho9305]

Anyone have links to sources for the "light text on a dark background is better" arguments? The tables on the bottom of this pdf seem to indicate that dark text on a light background is better. This site claims, "Usually, black text on a white background is the least stressful to read for extended periods, although some people prefer green on white. The most stressful is white or yellow text on a dark background."

Personally I prefer dark text on light backgrounds. When I read reviews on HardOCP I notice the bright lines of text burn into my retina (if I move my eyes, regions where text were appear darker than the surrounding regions).

It does this by suppressing neural signals from cells adjacent to cells which are picking up higher intensities. So, if I have a black line on a white background, the border of the black line will appear gray. If I have white letters on a black background, the edges will become more clear and well-defined.

I don't buy that. My understanding was that the suppression worked about the same either way - some ganglia are sensitized to "dark inside bright outside", and others are sensitized to "bright inside dark outside" (see this picture).

 

[Mark R]

Another important advantage of a dark background is the increase in contrast sensitivity; the presence of a bright background results in light scatter in the optics of the eye - a phenomenon known as veiling luminance. The more background light there is, the more will be scattered into the dark areas. (Contrast perception is approximately logarithmic, and the smallest perceptible difference is a change of 0.5 - 2% depending on the source - so minimizing scatter into the dark areas of vision is critical to maximizing visual contrast). This is the reason that watching TV in a darkened room allows you to see more detail.

When considering presentations, it's also important to consider the audience's attention. A black or very dark background isn't conducive to keeping your audience alert, and some illumination is helpful unless you are presenting images where viewing conditions are important (although as this is my line of work, in practice, I've yet to find a projector that is even remotely close to calibrated, making this point moot). There is also an issue with depth of field; I think I'm getting old and I can no longer read the text on presentations with a dark background from the back of the room, as a result of the shallow depth of field offered by dilated pupils and loss of accomodation. (Ignoring the fact that this may be a sign that I should visit an optician).

 

[CycloWizard]

Originally posted by: CTho9305
I don't buy that. My understanding was that the suppression worked about the same either way - some ganglia are sensitized to "dark inside bright outside", and others are sensitized to "bright inside dark outside" (see this picture).

I taught Hartline's experiment in a neurophysiology lab with his academic grandson, who explained it all to me. I might even have a cool video that demonstrates the principle if I can find it... It's possible that the horseshoe crab is different (indeed, it is in some ways, since it only sees in black and white due to the presence of only a single opsin species). In any case, walk around an ophthalmology research conference and look at the posters of everyone who studies the retina. You'll notice that all of them are light letters on dark backgrounds.

 

[AleleVanuatu]

You can save more by turning down the brightness on your LCDs. Check your watt meter and see the differenCE!