Power-Saving Web Pages: Real Or Myth? 424
An anonymous reader writes "Are dark webdesigns an energy saving alternative to a snow white Google? The theory is websites with black backgrounds save energy, based on the assumption that a monitor requires more power to display a white screen than black. Is this a blatant green washing ploy by Blackle.com, or an earnest energy saving tweak for a search tool we use every day? To find out, PCSTATS hooked up an Extech Power Analyzer to a 19" CRT and a 19" LCD and measured power draw — turns out there is a not insignificant difference ..."
Seriously? (Score:3, Insightful)
Did anyone here actually believe this? The big power draw is from the backlight, which is still running even with black pixels.
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I bet "Anonymous Reader", our submitter, who probably shills for "blackle.com", "believes" it.
I can't decide if this story is an intentional slashvertisement or an astroturf.
"Blackle.com"? Really? It's only slightly clever to raise the possibility that they're trying to greenwash the issue of "website-specific power consumption", especially since TFS very conveniently refutes that. ("not insignficant?" Sheesh.)
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Unless the screen is OLED, the answer to "does dark sites save power?" is a flat out NO.
That being said, reading white text on a black background looks a lot better on monitors because the entire background is not light emitting.
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You realize that CRTs use less power with darker images for basically the same exact reason?
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I like reading black on white. With white text on black bg I have afterimages of text lines and this is sometimes rather confusing when trying to read text with another line spacing.
Re:Seriously? (Score:5, Informative)
Unless the screen is OLED, the answer to "does dark sites save power?" is a flat out NO.
How you do figure, where's your data? Their data clearly shows that a CRT displaying all white uses 85W, and the same monitor displaying all black uses 63W, which sounds to me like it's using 25% less power to display the black screen. For an LCD the difference is only about 10%. The grayscale comparisons clearly show a relationship between darkness and power draw.
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Have you actually visited blackle.com? It is just a Google search box with a black background. No advertising, no agenda other than someone who seems to have a genuine point.
Even LCDs seem to benefit to the tune of 10% energy savings. 10% over thousands or millions of computers is a lot.
It would be interesting to see stats from more monitors, and also from mobile phones with OLED screens. I have a feeling that the Samsung monitor they tested is one of the smarter ones that reduces blacklight levels when the
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Did anyone here actually believe this? The big power draw is from the backlight, which is still running even with black pixels.
No, the big power draw is from CRT displays.
Both of them. They'll die someday and things will be nice and green again....
Re:Seriously? (Score:5, Funny)
No, the big power draw is from CRT displays.
Both of them. They'll die someday and things will be nice and green again....
Back in my day the CRTs were green... or sometimes amber.
Re:Seriously? (Score:5, Informative)
Yes, anyone here actually believed this. I guess in your hurry to post, you misread the double-negative in the summary...
Note that their measurements apply specifically to the two models they tested, a CRT and a particular LCD.
If 'white' means you have to drive the LCD, then white takes more energy. If 'black' means you have to drive the LCD, then black takes more energy. Most LCD drivers are standardized, though - and given the prevalence of lighter content, it may be worth it to the industry (even if only so they can use it in marketing) to switch the defaults.
Re:Seriously? (Score:4, Informative)
The link was to pcstats.com, which actually tested the claim. There was a ~25% difference between all-white and all-black screens on their test CRT, and a ~12% difference between the two on their test LCD.
They tested a lot more sites than just Google and Blackle.
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I am fine with this data being spread and loads of websites switching to white text on a black background. I think it looks cooler, and moreover it is way, way easier to read. Sometimes the white background of a screen just assaults the eyes.
Re:Seriously? (Score:4, Informative)
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I've never understood this argument they had about black bakgrounds. The backlight is always on and hence why we should all be using LED or the newly available translucent monitors that use ambient light. I think the myth is due to our perception of light & dark. We fail to understand black on a monitor is a lack of color and an absorption of all light but the backlight as stated operates independently of the display's image.
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No, the power draw is from the heaters and the deflection circuitry, but each gun that is turned on at full intensity also adds to the total (that's why full screen yellow uses more power than full screen red or green).
Re:Seriously? (Score:5, Insightful)
The LCD they tested is also 8 years old [google.com].
I'm not saying newer LCD screens would perform differently (dynamic contrast, local dimming, etc. == marketing stats boosting and terrible) but basing a blanket statement like "B) Websites with darker colours tend to cause the monitor to consume less power." on a test with one LCD monitor is stretching it.
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Did anyone here actually believe this?
I dunno...but I DO know my eyes are funny for a few minutes after I try to read any amount of white-on-black text - it causes massive afterimage.
(Yes, I have the "nostyle" Firefox plugin to deal with these websites)
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Actually, it can. Modern LCD displays are crap at this - they employ crap like "local dimming" and "global dimming" to get their stupid contrast ratios. As a side effect, displaying a dark screen does save power because the backlight dims to make the black blacker.
Conversly, displaying a white screen cranks up the backlight to make it brighter, which takes more power.
Since contrast
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Other thing... white on black is hard on the eyes because of "black creep". If you're a typesetter, you know this - if you have light text on dark background, you have to increase the siez of the text in order to keep its apparent size the same. Also, thin fonts sink, so you may have to apply bolding to "fatten" them so they're still legible when the black background slims them down.
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Re:Seriously? (Score:4, Informative)
So they show a 1.6 watt difference (LCD) on the same image, where their stated difference between google and blackie is 3.8 watts.
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That's not inconsistent. It's called error, or noise. Never trust a value with no error bars.
Really? (Score:3, Funny)
Oh god. I was wondering why my screen randomly seems to increase/decrease in brightness.
I hate this feature. It makes me think someone slipped me some acid, and then I'm disappointed, because no, it's just bad attempts at saving power.
Re:Really? (Score:5, Informative)
No, it's not. It's supposed to make the screen feel like it has a higher contrast ratio than it actually does.... and has nothing to do with power consumption.
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.... and has nothing to do with power consumption.
Really? My external monitor at work defaulted to "Energy Smart Mode" (until I turned it off) which means "Dynamic dimming activated". I wouldn't say it has nothing to do with power consumption.
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I guess then it's intended to do what marketing says it is. I wonder what the actual intent was when the idea was brought to the table?
Re:Really? (Score:5, Informative)
Well, he probably wasn't aware exactly which model of monitor you had. Generalizations tend to be bad for this reason.
I, for example, have an LCD projector with a dynamic iris. It dims the bulb for dark scenes, and it is only for the improvement in contrast ratios. I know this, because it doesn't dim the bulb by decreasing the voltage over the filament, but by closing shutters (the iris) between the bulb and the LCD panel. It's described in more detail here [projectorcentral.com]
I don't know the full history of the feature on monitors, but I'd assume it was originally to increase contrast ratio. After one marketer slapped a "energy efficient" sticker on the box, the manufacturers realized the marketing benefit of the feature, and probably renamed the menu for later models.
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Yeah, but you can dim the fluorescent lamp without changing the spectrum too much. WIth your projector, I'm guessing by your use of the word, "bulb," that you have a blackbody emitter as the light source. Reducing the power reduces the light output, but also changes the peak wavelength - http://en.wikipedia.org/wiki/Planck's_law [wikipedia.org]. There are a few ways to handle this, but the iris is probably the most practical.
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It's a poor attempt at making the monitor have the same black levels as a CRT. Of course, a CRT would have the same black level whether the rest of the screen is white or black. It is not as good, but at least it is a step in the right direction. Ideally each pixel would have its own light source that is separately controlled.
Another way of achieving good contrast ratio is increasing the maximum brightness, after all, there is a large ratio between a 100W lightbulb and the sun...
Re:Really? (Score:4, Interesting)
You should hate it. It's a shitty hack to make it look like your LCD has better contrast on paper.
I briefly owned a display like that. If I turned the dynamic contrast off, it looked washed out, and no amount of tweaking would get it looking even halfway decent. It was a shitty LCD but it was also 1/3rd the cost of my current photorealistic dazzlers.
It's the visual equivalent of the bass and treble boost knobs on cheap stereos.
Blackle seems all well and good... (Score:2)
Double Negative (Score:5, Funny)
"turns out there is a not insignificant difference "
Double negatives are not not bad.
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In this case, the double negative has a valid use. By saying "not insignificant" it leaves all other possibilities except for insignificant. This doesn't necessarily mean that the difference is significant, just that it isn't insignificant. If they said there is a "significant difference" then they have left only one option - that the difference is significant, and that statement carries more weight.
OLEDs and readability (Score:3)
So the answer is... (Score:4, Insightful)
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The time-honored metaphor for this is "carefully arranging the deck chairs on the Titanic as it sinks." We can fiddle trivial stuff and satisfy ourselves we're "DOING SOMETHING FOR <great cause>" while not actually changing the costly, momentous, or personally-significant things.
See also Matthew 7:3-5 if you're not opposed to Biblical proverbs.
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Well if you already did that....
Frankly, I wonder why they didn't test the one thing I do as soon as I get a new LCD, which is actually recomended by several sites out there.... turn the brightness down to under 20%, sometimes, I go all the way to "0" (interesting that 0 brightness is not a black screen).
As an N=1 test, after realising that I couldn't easily tell the difference after a minute or two, was to take one of the most observant and territorial about her PC people I know, and changed the brightness
OLED's (Score:4, Informative)
The idea is valid for all of the smartphones running OLED displays. OLED's take no power (or very little) to display a black pixel. It takes full power to display white.
AMOLED? (Score:2)
Power is more of a concern on mobile devices and mostly dark/black displays will allow AMOLEDs to turn off some pixels to save power and extend battery life.
I should have submitted this too... (Score:5, Insightful)
"Are not dark webdesigns an energy unsaving alternative to a snow white Google? The theory is that websites with black backgrounds don't save energy, based not on the assumption that a monitor requires more power to display a white screen than black. Is not this not a earnest endeavor by Blackle.com, or a not earnest not green not washing not not not not not ploy by not Blackle.com? To find out, PCSTATS didnt't not hook up an Extech Power Analyzer to a 19" CRT and a 19" LCD and measured power draw — turns out there is a significant difference ..."
Mine would have been shot down for being too readable though.
Webpage almost crashed IE8 (Score:4, Interesting)
Maybe PCstats should apply their own power-saving strategies to themselves (less CPU-intensive flash crap).
Anyway it appears only the CRT has a significant savings with White google versus Black blackle.com. LCDs gain almost nothing.
For one person, no - but... (Score:2)
I'm not really double checking my #'s here....
1 billion queries per day in 2011 (quick online search)... lets say that 1 user makes 100 queries/day (so 10 million users) and each query takes about 10 seconds to complete. 100 million seconds burning 4 watts yields 400 megawatts per day. If we average that out per hour, then we're burning 16 megawatts per hour 24/7. Each day, enough to power 8-16 households (1000-2000kwh) for a month... so over a month: 240-480 households with pretty wasteful practices.
SO,
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Could you explain what megawatts per day means?
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a single day of queries (1 billion), ended up (in my calculation) resulting in using 400 megawatts. so, 400 megawatts being used per day.
I'm finally green!!!! (Score:3)
Yay! My Black Sabbath fan site is one of the most environmentally-friendly sites on the internet!!
So do I win some kind of a prize? (Score:2)
I've been running MessageBase [messagebase.net] with a black background because of this exact reason since the late 1990s. Everyone told me it was a stupid idea and the power savings were negligable.
Think of all the power I've saved people! I've done my part.
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It's not just good for power. It's hard to stare at a white backlit source for a long time. Muted colors on a black background are the easiest on the eyes.
Their own number don't even agree... (Score:2)
Re:Their own number don't even agree... (Score:4, Insightful)
Web pages with FLASH waste more power.
Grey levels? (Score:3)
Anyone else notice that (further down in the article) they measured 6 different levels of grey between 'white' and 'black', and 4 of the levels of grey actually measured MORE of a power draw than pure white on the LCD monitor?
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Shadowing the backlight consumes some power in LCDs, except if the part is dark enough so they can dim the light in that sector.
Re:Grey levels? (Score:5, Insightful)
That's not so strange in electronics.
Take FETs - undriven they're fine, saturated they're fine, but the Ohmic region you typically (when using it as a switch) want to stay out of because the FET's just going to burn the excess off in the form of heat.
There's a bunch of reasons why some regions may take more energy than others. I wouldn't know what the reason is for the panel they used, somebody more intimately familiar with driver design and panel response would have to chime in.
The real power-saving web pages (Score:5, Insightful)
Re:The real power-saving web pages (Score:4, Informative)
The best enegery saving, battery-life extneing thing I've done is to use FlashBlock. (Or in Chrome set it up to not load any extension without a click.) This has been the difference between getting 8 hours out of my laptop and getting 2 1/2.
Now if only web pages would be smarter about using setTimeout [mozilla.org].
What about the CPU? (Score:5, Interesting)
Firstly, I'm extremely skeptical of one of the conclusions - 'flash will make a CRT monitor use more power' - which I just don't believe - it will use an amount of power dependent on the average screen brightness - which may be an increase over black.
LCDs are different - the panel does actually take some energy to change state, and the lag compensation circuitry will use more in motion.
Secondly - a huge part has been missed out of this.
Power consumption of the computer.
Flash, or javascript, even in the background, can considerably increase power.
For example, I just closed all of the flash/animated things in the background on other tabs in firefox, and the CPU usage is now bouncing around 2%, with the computer using 17W.
If I start up a new tab with some flash, and gif animations, it goes up to 25W. (+8W)
Even switching away from the tab only takes it to 23W or so. (+5W)
It would be interesting to work out the total electricity wasted by common flash ads.
Mobile Applications (Score:3)
What about the rest of the computer ? (Score:4, Interesting)
It would have been interesting to include the whole computer in the power measurement. How much more electricity is drawn by a javascript infested site than one that is just static HTML and images ? How much more is drawn if there are 100 components to build the page instead of 20 (don't forget to include the consumption of your broadband modem, etc, ...) ? How much more electricity does flash use ? How much more through heavy use of AJAX ?
The biggest difference that they showed was that the use of a glass monitor was about double that of a LCD. With an LCD the CPU/... consumption would be a bigger fraction of the whole thing.
Is this even a thing? (Score:2)
Depends on your definition of significant (Score:2)
A 11% difference between full white and full back is more or less insignificant to me.
2 issues with smartphones (Score:2)
Some phones have OLED screens that consume less power when displaying dark colors.
Another reason is nighttime usability on a smartphone. Too much light is blinding after your pupils have dilated to accommodate the dark.
Reduce http hits and HTML complexity first? (Score:2)
Meh... What I'd want to know is, by how much do you decrease a site's power consumption when you strip out:
1. Needlessly complex HTML. (sidebars, header, footer, occasionally content...)
2. Scripts, CSS files and cookies from all over the place (I'm looking at you, ads)
Or to put it another way: Give me what Safari Reader gives me, plus a few nav links, and I'll be happy.
Offset against heating costs (Score:2)
Save even more power (Score:5, Funny)
If they want to save power... (Score:3)
How about less Java, flash, and videos?
CPU and network still takes power, too...
Energy usage generating the page? (Score:3)
Re:Watts aren't a unit of energy. (Score:5, Funny)
If you wait a few seconds, your watts will turn into joules.
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if you cross the Atlantic, your Joules will turn into ergs
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I always thought ergs were a unit of frustration. For example, doing energy based calculations in Imperial/US customary units is a ton of ergs.
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Think of electricity as waves crashing against the beach. Amps are how tall they are, volts how many are arriving in a frame of time or frequency. Watts is a measurement that gives a volumetric answer to power usage. It's a perfectly valid way to measure since we pay based on wattage per hour.
Re:Watts aren't a unit of energy. (Score:4, Informative)
Amps are how tall they are, volts how many are arriving in a frame of time or frequency.
Not that it affects the product (charge/energy), but amps measure transfer of charge over time, and volts measure electrical potential energy, so volts should be the height of the waves (gravitational potential energy) and amps the rate of arrival (in terms of volume of water per unit time, not waves per unit time).
It's a perfectly valid way to measure since we pay based on wattage per hour.
I don't know about where you're from, but around here we pay for energy in watt-hours (1 W*h = 3600 J), not watts per hour.
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the difference is just 17.7W and 3.8W for CRT and LCD respectively. What that adds up to over the course of a year, for every second you spend doing a search on Google is anyone's guess.
That was my favorite part. I'm guessing they just hooked up a some kind of Kill-A-Watt given that:
PCSTATS has an electronic power meter which can actually measure the amount of energy it takes a monitor (LCD and CRT) to display any given website, we've actually got a valid set of criteria to look at.
Never mind the nomenclature, there is cost forecasting on those devices, and given a few basic parameters you could figure out the cost per year searching Blackle rather than Google on the back of a napkin, so its not "anyone's guess".
price_per_killowatt_hour: $0.10
hours_searching_google_per_day: 2 hrs
watts_saved: 17.7
hours_searching_google_per_year = hours_searching_google_per_day * 365
kilowatthours_saved_per_
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times 300 million.
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>> Voltage mutiplied by current in Amps equals Watts.
NO. For God's sake will people stop making this mistake.
Voltage multiplied by current in Amps equals VA, not Watts. If you want watts, you have to multiply Voltage in Volts, Current in Amps, and the cosine of the angle between them (which is more commonly known as the power factor.
VA = V*A
Watts = V*A*PF
Re:Watts aren't a unit of energy. (Score:4, Informative)
>> Voltage mutiplied by current in Amps equals Watts.
NO. For God's sake will people stop making this mistake.
Voltage multiplied by current in Amps equals VA, not Watts. If you want watts, you have to multiply Voltage in Volts, Current in Amps, and the cosine of the angle between them (which is more commonly known as the power factor.
VA = V*A Watts = V*A*PF
No, Watts is really Voltage times Current. But when referring to AC systems, definitions get all screwed up. Just look at "kWh" - what a mess. It's like electricians have their own definitions for these units. I suppose it is understandable - using a single number to approximate a waveform and then performing calculations using Ohms Law makes most tasks much easier.
So pointing out the difference between Watts and VA is good - thanks for that. But don't be calling the real definition for Watts wrong. Also, your definition for power factor is not correct - or at least it is dated. It only applies to AC systems where the waveform is shifted. Power factor also applies to waveforms that are modified in other ways. For example, a computer power supply without power factor correction consumes pulses of power during the peak points of the sine wave. This changes the shape of the wave without resulting in a phase shift. With power factor correction, a control circuit draws power throughout the entire waveform so that the sine wave is not distorted.
I wonder what they used to measure power usage for this test. Did the instrument record true RMS power? Those instruments are much more expensive but required for accurate results. Guess I should rtfa.
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With AC power the parent is correct. However I think the power factor used by most devices is over
Re:No shit... (Score:4, Funny)
There is a not insignificant parsing complexity.
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I don't really see the problem with "not insignificant".
Just because something is "not insignificant" doesn't make it "significant".
Say I give you a papercut. You'll be in a "not insignificant" amount of pain.. in fact, you'll probably curse me all day long.
But it's not exactly a "significant" amount of pain either.. it's not like you're curled up on the floor begging for somebody, anybody, to put you out of your misery or at least give you an OTC painkiller.
Perhaps a completely alternative term could have
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How about 'small'.
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Re: Yes way shit... (Score:5, Insightful)
The above post has incorrect assumptions.
Standard LCD screens do not alter the intensity of the backlight based on the information displayed on the screen, and the backlight and it's inverter is the majority of the power consumption. In addition, the drive circuit that aligns the liquid crystals can work opposite from how you expect in a TFT. Most TN screens, for example, are white or light gray when unpowered - refreshing the pixels to a black state takes more transistor drive than making the screen white. This is the technology you will find in most portable devices and computer monitors.
Some LED-backlit TVs use dynamic backlight, or even zone-dynamic backlight, where (mainly to create ridiculous contrast ratio specs) the backlight is reduced to the maximum temporal white level needed, or for multi-area addressable systems, the brightest backlight needed in an area.
The only portable devices where the brightness of the screen data is directly related to energy consumption would be those with OLED screens (such as the Samsung Galaxy SII line). The individual pixels are miniature LEDs, and when a pixel is black, they are turned off. On these AMOLED display phones, a black wallpaper can use far less power.
When I think of "power-saving webpages", I may be more concerned about one that runs my CPU at 100% for several seconds to display a page, Slashdot.
Re:No shit... (Score:5, Funny)
It is obvious that black is good for the earth and white is bad.
Why do you think we have climate change? Because of white, of course. No one has even heard of climate change before white messed everything up.
Not only is white bad, white is unhip. What do you want at your disco? White lights? No, black lights produce the right mood.
Let's fight the white and save the world!
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Re:God is my salvation. (Score:4, Insightful)
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CRTs per se may not be useful much anymore but plasma certainly is!
Re:CRTs? (Score:5, Interesting)
People still have CRTs?
How ridiculous.
Ability to display perfect black color;
Ability to display more than one resolution correctly (useful for games, old video card = new games at reduced resolution);
Ultrafast response time, no input lag;
Reliable and have long life (people saying things like "My LCD started acting weird, but it's 3 years old, time for a new one", while my 12 year old CRT works great), but can also be repaired if necessary (well, other than the failure of the tube obviously);
More affordable than a 24" LCD that can display 2304x1440 (if such a thing even exists);
Great image quality.
The only advantages of LCDs are size, weight and power consumption - all of these are not primary features of a monitor, at least for me (the same way that I don't buy a car based solely on the fuel consumption, or a computer based on its power consumption and size - I look for performance and cost first).
Re:CRTs? (Score:5, Funny)
The only advantages of LCDs are size, weight and power consumption - all of these are not primary features of a monitor, at least for me (the same way that I don't buy a car based solely on the fuel consumption, or a computer based on its power consumption and size - I look for performance and cost first).
The LCD advantage that I prefer? Not irradiating remaining eye.
Re:CRTs? (Score:4, Funny)
CRTs have big geometry problems...
CRTs also take up so much space that is ridiculous.
Is that not also a geometry problem?
Re:even more savings (Score:4, Funny)
But the characters are black, so each one represents energy saved.
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My first question after reading the synopsis was, "Does anyone really fucking CARE about this?"
I mean..this is minutiae.....
Re:even more savings (Score:5, Insightful)
this is minutiae.....
3.8W is hardly a minute amount of power. If I did my math right, it's approximately the amount of power it takes to lift a full soda can (~390g) 1 meter in 1 second.
Let's say each Google query takes 10 seconds of viewing time, so you could save 38 watt-seconds per query by going black. Multiply this by 3 Billion queries per day, times 365 days/year. That's 12GWh (to 2 significant figures) of electricity that could be saved annually by changing a couple lines of code.
Power costs around $0.10/KWh. I don't consider $1.2M/year to be a minute amount of money.
Re:even more savings (Score:4, Insightful)
No. The amount of fuel your power plant uses is proportional to the power it is supplying. In case of coal plant: there is less coal being burned, in case of hydroelectric: less water needs to go through the turbines, in case of nuclear: control rods are inserted into the reactor core to slow down the reaction of the fuel rods by absorbing neutrons.
Less power used = less power generated = less fuel used.
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The amount of fuel your power plant uses is proportional to the power it is supplying.
Only to a certain extent. You don't turn on and off furnaces on a coal/gas plant just because demand dropped. Most of those plants burn fuel (a ton of it) regardless of their production being in active use or not.
Hydro plants are more dynamical, but you still have a baseline water consumption value (the minimum needed to keep a turbine working), and turning them on and off isn't instantaneous either. Most hydro generation is done in dams, so you usually need to maintain a minimum flow of water (usually eno
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i'm pretty sure black uses more energy in lcds than white, because the power is used to mask light, not generate it, so a completely white screen might save more power in modern screens than black, though i don't know about more modern technologies like tft. new led screens are probably also opposite, so any power-saving web page would have to detect the type of screen (lcd or led)
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They just might know English better than you... (Score:3)
Ah, for the days when most people were literate enough to recognize, never mind use, rhetorical devices like litotes [about.com].
Readability: yes, please. (Score:4, Interesting)
Oh, so very, very much this.
Let me count the problems with light-text-on-dark-background:
1) If you have cataracts, corneal irritation, or smudged glasses, bright objects against a dark background are MUCH harder to resolve than dark images against a white background. With black-on-white, you just get reduced contrast; with white-on-black, you get distracting smears and rays all over the page.
2) In a dim room, your pupils dilate more if the scene before you is mostly dark, and dilated pupils generally produce poorer acuity. A bright background causes your pupils to contract, and just like stopping down a cheap camera lens, it improves the focus of the image hitting your retina.
3) In a bright room, a mostly-dark display will be more obscured by reflections and glare.
This is one reason I stopped hanging out at dpreview.com. Yeah, I know, photographers think their stuff looks better against a black background, but more than five or ten minutes on the site gives me a headache.