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programming and human factors
by Jeff Atwood
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If you've invested in a quality monitor for your computer, you owe it to yourself-- and your eyes-- to spend 15 minutes setting it up properly for your viewing environment. I'm not talking about a high-end color calibration, although you can certainly do that. I'm talking about basic computer display calibration 101.
The first piece of advice is essential -- make sure your LCD display is connected to your computer via a digital connection.
The DVI port, on the left, is the one you want. Avoid using the standard analog VGA connector, on the right. A DVI connection guarantees that your display is sent a pure, digital stream of bits, shuttled directly from your video card with no analog impurities introduced along the way.
In the bad old days of analog CRTs, we had to worry about a whole host of analog issues with the monitor itself, such as convergence, display curvature and geometry, refresh rate, bloom, resolution sizing, and so on. Every time I bought a new CRT, I'd spend a solid hour going through Nokia's classic monitor test program, adjusting monitor settings to reduce all the unavoidable analog side effects of an electron scanning CRT. It was a tweaker's paradise.
The good news is that a digitally connected LCD is much closer to perfect out of the box than any CRT ever was. There's very little tweaking necessary to get it looking its best.
Display calibration probably isn't anyone's idea of a good time, but it can be relatively painless. One of my favorite basic display calibration wizards is the one built into Windows Media Center. It's accessible via Settings, TV, Configure Your TV or Monitor. It's based on a series of brief, themed video clips that do a great job of explaining why each setting matters without bogging down in display-geek terminology. There are five sections:
The first two are mostly irrelevant for a digitally connected LCD display, provided you're running at the native resolution of the LCD display. I'll assume you are. The last three are the only adjustments that typically matter on a desktop LCD. I'll summarize each, along with a static screenshot from the video, so you can follow along on your display.
3. Brightness (Black & Shadow)
Locate the brightness control for your display. Adjust the brightness, making sure you can distinguish the shirt from the suit. The suit should be black, not gray. If you see a moving X, turn the brightness down until the X just disappears.
On a LCD, the brightness control doesn't have quite the same meaning as it does on a CRT. If your LCD has a gamma adjustment, that will be more effective at bringing out the nearly-black details on the shirt than increasing the backlight intensity will. Also, if you're looking for that X, you won't find it. I had trouble capturing the very dark moving X in my static screenshot for some reason. I've seen a very similar calibration technique used in video games which rely on dark environments. The goal is the same-- we want to see the deepest possible blacks on our display, without losing details in the darkness.
4. Contrast (White)
Locate the contrast control for your display. Set the contrast as high as possible without losing the wrinkles and buttons on the shirt. Lower the contrast if the white cue stick does not appear straight and smooth.
Digital fixed pixel displays won't have blooming problems, so you can ignore that last bit about the stick. But you can see where this is a complementary operation to the brightness adjustment we just made-- we want to see the brightest white details on our display, without blowing them out.
5. RGB Color Balance
Locate the RGB color balance control for your display. If your monitor has a color temperature setting, set it to 6500k (sometimes called "Warm" or "Low"). Make sure none of the gray bars have a tinge of red, green, or blue. You may need to fine tune brightness and contrast again after adjusting the color balance.
And that's it. A few minor adjustments to the Brightness, Contrast, and Color settings of your monitor is all it takes to get the most out of today's LCD displays-- to see all the colors, and the entire range of light to dark, that you paid for.
You should always start with the controls on the monitor itself. Unfortunately, some monitors won't allow you to change the brightness, contrast, and color settings in digital mode. Or perhaps you can't quite get the precision you need from the monitor's controls. Most video drivers will allow you to change these settings at the video card level.
Be careful, however, as there are usually two sets of settings: one for video playback, and the other for your desktop itself. I'd avoid changing brightness, contrast, or color settings via the video driver unless you have no other choice. It adds another layer of complexity to an already complex situation.
The general calibration steps for a LCD television are awfully similar to the Windows Media Center wizard I outlined above. But both are still rudimentary. You'll need to do much more involved calibration for professional color work.
These calibrations are also video-centric. It's an entirely fair point to note that we are talking about LCD computer displays here, and not LCD televisions. They aren't the same thing. People spend far more time reading text than watching videos on their computer monitors-- and at a distance of two feet, not ten feet. You might find that an optimal brightness for the above test images produces a screen that's painfully bright for workaday reading tasks. This is an important point that's glossed over in most LCD reviews, but Dan covered it with aplomb in his 30" Dell LCD review:
The minimum brightness setting for the 3007WFP-HC is still pretty bloody bright. The maximum brightness is down a bit from the non-HC model, at a mere 300 candelas per square metre, but that's still outrageously bright. Not nearly as bright as sunlight on paper, but way brighter than anybody should set a normal indoor desktop monitor.Ideally, your monitor shouldn't be any brighter than a well-lit book (something which is probably new to the 60Hz-CRT brigade who, today, don't know how to adjust their laptop's screen brightness...). But I can't turn the 3007WFP-HC down that far. Well, not without opening the thing up and fooling with the backlight power supply or something.
I've rigged up a quick-'n'-dodgy bias light behind the monitor to reduce eyestrain, and JediConcentrate and the Darken bookmarklet help to reduce the number of minutes I spend with millions of bright white pixels tanning my retinas.
Far too much default brightness is easily the number one problem I see on most LCDs these days. Keep Dan's rule of thumb in mind as you're adjusting the brightness and contrast on your LCD against the reference images. Most display calibration guides care only about accuracy, not your eyeballs. For reading purposes, your monitor shouldn't end up any brighter than a well-lit book.
Some DVI also carries analog signal. It's a bit deceiving though. If you have a DVI LCD doesn't mean you'll be getting digital. Mostly it's the earlier generation of LCD. The DVI connection you shown above it's 24+1 (Dual Link). The digital+analog version of DVI will have the extra 4 pin on the right hand side, making it 24+5 (DVI-I). Analog version only will have 12+5 (DVI-A). This latter one can't even be plugged into the DVI port you shown above. Sad
Faulty on October 1, 2007 4:12 AMBtw, DVI-VGA converter is just merely connecting the analog signals.
Faulty on October 1, 2007 4:30 AMHelpful! But don't forget that a useful alternative to adjusting the brightness of your monitor is to post a stream of blog posts and comments demanding that every website in the world change to using white-on-black text in order to stop hurting your eyes...
R Mutt on October 1, 2007 4:42 AMHere's a hardware horror for you. My company recently replaced my crufty ancient desktop with a snazzy new one, including replacing the 1024x768 CRT with an LCD, with both VGA and DVI inputs. The new box also has a video card on it that will apparently pump out up to 2048x1536, via DVI only.
But... the CRT is hooked up to the MOTHERBOARD video (max 1280x1024), with an ordinary VGA cable!
Dave Aronson on October 1, 2007 5:49 AM(er, duh, I mean "the monitor is hooked up", not "the CRT is hooked up"... it ain't no CRT no mo'....)
Dave Aronson on October 1, 2007 5:50 AMAmusingly, my Dell FPW2405 has a DVI input, but the functionality is crippled when you use it. In analog mode you can tell it to preserve the aspect ratio of anything it is sent or not. In digital mode it forces everything to the ratio of the screen and disables the menu option. So any games that don't support wide screen resolutions look stretched and you are forced to resize any non-widescreen videos on the PC side before they are sent to the screen.
a on October 1, 2007 6:18 AMMany of the new Dell PCs I setup come with LCD screens with DVI inputs and cables, but VGA only on the PC.
Allied on October 1, 2007 6:27 AM@a If you investigate your graphics card settings there will almost certainly be an option to have the graphics card set the aspect ratio, rather than the monitor. The nVidia control panel certainly does - as far as the monitor is concerned it always gets a full resolution signal, but the graphics card is using its internal scaler letterbox or scale as appropriate to provide the correct aspect ratio. No more ugly stretching (and no gaming performance hit either if your worried).
Mal on October 1, 2007 6:47 AMMy new HP came with an LCD (though I upgraded to a bigger LCD), and VGA only on the computer. It does have an PCIe slot, but all of the video cards I have laying around are AGP (though all of the cards I've purchased in the last 6 or so years have DVI outputs).
Guess I'll be springing for a new video card eventually, though I've been planning on doing that since I brought the PC home and realized there wasn't anywhere on the computer to hook up the damned cable.
Vizeroth on October 1, 2007 6:48 AMWhatever. I have never noticed the difference between hooking up an LCD to DVI vs. the HD15. Unless I just have crappy monitors, which is entirely possible.
John Radke on October 1, 2007 7:05 AMYou state that brightness is the number one problem you see with LCDs but I had the opposite problem. As a gamer I had issues with how my monitor looked washed out compared to the exact same monitor my wife had. It took 6 months before I found out that Vista has a "nice" little option that alters between "normal" display and "movie" display. Movie display is what the normal one is and the reason my monitor looked washed out compared to hers no matter what I did. Video card options, display options, monitor options, NOTHING except this one little checkbox hidden deep within Vistas controls would change this. Just a heads up if your monitor isn't displaying as well as you think it should and you run Vista.
Cybercat on October 1, 2007 7:21 AMFor those people out there not convinced of the benefit of DVI over VGA, I suggest you try this test some time if you can access the equipment:
- Get an LCD panel with both a VGA and DVI input (many Dells, for example).
- Get a PC with a video card that has both VGA and DVI output.
- Connect both the VGA and DVI connections.
- Switch between the two inputs on the monitor and note the difference.
I tried this when working helpdesk some years ago and having access to such equipment. The difference was totally night and day, DVI is just far superior especially when it comes to crisply rendering high contrast edges and text.
Also, I should point out that on most LCD's the "brightness" control isn't really quite the same thing as it was in the CRT world. On a CRT, the brightness would actually adjust the black point of the output to the screen. On an LCD, the brightness control is usually just the intensity of the backlight, the black point of the pixels themselves remains the same.
Furthermore, if you want to properly calibrate your monitor, I suggest picking up a hardware calibrator like the Spyder2 Pro. The Express version is only around $100 dollars and it really does make a noticeable difference when it comes to accurate color rendering. If you have multiple monitors and want to calibrate them all (I'm looking at you, Jeff) you'll have to shell out a bit more for the Pro version.
Kamil Kisiel on October 1, 2007 7:46 AM@DVI connection
I am in the market for a new laptop Anyone know of any Non Apple laptops that have DVI out ? I dont mind carrying dvi->vga for presentations but when I am at the office I would like ot hook my notebook natively to my dell 27" display. I know asking for dual DVI out for a 30" display is all but non-existant
Mike Johnson on October 1, 2007 8:16 AM"Many of the new Dell PCs I setup come with LCD screens with DVI inputs and cables, but VGA only on the PC."
I've just got a Dell for the family when I move away and noticed that too. In this case it was fortunate though because I'm taking the (far superior) monitor with me and my computer has DVI output.
[ICR] on October 1, 2007 8:34 AM@Dave Aronson:
I've hit the same problem a couple of times while working in the offices of other companies: perfectly good DVI connections available on the PC and monitor, but analog cables connecting them.
Naturally obtaining a DVI cable through official channels would mean forms filled out in triplicate and battles with the "it ain't broke, don't fix it" droids.
So instead I just bought my own cable which I smuggle in with me whenever I move to a new office.
(Unfortunately I'm currently working at our main office, where I have a nice widescreen HP L2045W, but no DVI connection available on my fairly recent HP PC. Maybe I need to smuggle in a decent video card next...)
Graham Stewart on October 1, 2007 9:03 AMI have the 3007WFP-HC, and run it on the minimum brightness setting to avoid eye strain. Another benefit of doing this is power usage. On the lowest brightness setting, I am typically pulling 63w at the wall vs. 93w for the highest (default) setting.
Derek on October 1, 2007 9:46 AMJohn Radke,
You have two crappy monitors. There is a definite difference between the two connection types on a good LCD.
Mac OS X has a built-in colour calibrator which uses a rather different technique, seen in the screen shots here:
http://www.computer-darkroom.com/colorsync-display/colorsync_2.htm
I hope it's clear to readers that the calibration images above should only be considered for demonstration purposes. Readers should calibrate their display using software made for the purpose, and not by viewing the Vista screen captures displayed in this web page.
Because of the display characteristics of the images, different web browsers, operating systems, OS settings, and hardware displays, they will be rendered differently on different systems. Calibration software either overrides the OS's colour rendering, or takes it into consideration when displaying the calibration image.
Do these image files have embedded colour profiles? Your OS or browser may, or may not assume an sRGB colour profile for non-tagged images. Your graphics software, e.g. Photoshop, uses a different colour-display engine, which makes different assumptions, and has many options for rendering intent. Does Vista's screenshot function saves the raw bits from the calibration video, or as altered by the OS's display calibration function?
> The difference was totally night and day, DVI is just far superior especially when it comes to crisply rendering high contrast edges and text.
DVI is the way to go, however, the quality of the analog VGA conversion in most LCDs has improved dramatically in the last few years. They're still inferior to a pure DVI connection, but the difference is not quite as extreme as it used to be.
As I mentioned in my post, some monitors disable almost all their calibration controls when in digital mode. My circa-2004 SyncMaster 213T is like that. When connected via DVI, I can *only* adjust brightness. Newer Samsung LCDs don't suffer from this defect, fortunately..
> Readers should calibrate their display using software made for the purpose,
It's true that calibration is a question of how far down the rabbit hole you want to go, but the three images I posted are a reasonable way to get started. Most people use their displays the way they came from the factory; any kind of basic eyeball calibration is better than that.
There are three flavors of DVI:
DVI-A: analog
DVI-D: digital
DVI_I: both
It seems DVI-I cables are pretty standard, since they support analog or digital (and can have a VGA adapter put on one end).
If you want to make sure you're in digital mode, most monitors will usually tell you if you go to their info screen. If you REALLY want to be sure, get a hold of a DVI-D cable and use that.
Bob on October 1, 2007 12:42 PM> any kind of basic eyeball calibration is better than that
Perhaps something is better than nothing, but is there no free colour calibration for pre-Vista versions of Windows?
Even a simple ramp of controlled grey patches might be an improvement over the photos of that sexy guy. In the following image you should see every tone, and just barely make out the alternating squares in the top strip (from a tutorial at http://www.digitalmasters.com.au/Monitor_Calibration.html):
http://www.digitalmasters.com.au/Brightness-sRGB.jpg
I also wonder if the Windows Media Center makes the same gamma curve and other assumptions for TV display as one would for general computer use.
If you highlight all solid-black pixels in the first, you will find that half of the X is indeed visible, over a mostly-pure black background—the background is so dark that the X is invisible (in fact most of the background is solid black #000). Similarly, in the white-shirt photo, about half of the shirt pixels have shifted to solid blocks of white #FFF. Although there are buttons and wrinkles visible, you can play around with colour controls all you want, but the flat areas will remain featureless. These are not good examples of continuous-tone photos. I think something may have happened in capturing the screen which bottomed out the dark tones and blew out the whites.
Michael Z. on October 1, 2007 12:46 PM> 5. RGB Color Balance
> Make sure none of the gray bars have a tinge of red, green, or blue. You may need to fine tune brightness and contrast again after adjusting the color balance.
That's a lot harder than it sounds. Your perception of correct white and grayscale colours on a display has a lot to do with what you've become accustomed to. After calibrating my monitor properly, everything initially seemed like it had a hell of a red cast!
Pino on October 1, 2007 1:31 PMIf all else fails, a Pantone strip helps.
Wish I knew of a free way of generating an ICM profile; even though I don't care about rigid calibration myself, I've had people ask about it.
Mike Johnson,
As far as I know most laptops these days (at least 14" and up) come with DVI ports. Maybe not ones with lesser integrated graphics chips. I know some high-end Acers come with dual-link, I think it's a standard feature of the higher-end mobility cards.
Great! Thanks for sharing this.
I had used the color tuner which came with nvidia's drivers and recalibrated my screen according to your tips... wow.. Where did all these shades of gray come from?!
Too bad the whole calibration video thingy isn't available in Win XP pro.
Jani on October 1, 2007 2:08 PMGreat article, but what's with the Gucci Male Models for the contrast/brightness check? Couldn't we just use diagrams? :)
Mark on October 1, 2007 2:08 PM> Also, I should point out that on most LCD's the "brightness" control isn't really quite the same thing as it was in the CRT world. On a CRT, the brightness would actually adjust the black point of the output to the screen. On an LCD, the brightness control is usually just the intensity of the backlight, the black point of the pixels themselves remains the same.
An excellent point. The brightness control is a very different thing on a LCD and a CRT. We should be looking for a *gamma* adjustment on the LCD, shouldn't we? I'll update the post to reflect this.
Good summary with animated black level GIF here.
http://www.drycreekphoto.com/Learn/Calibration/monitor_black.htm
Jeff Atwood on October 1, 2007 2:58 PM@Mal Thanks, apparently it was an NVIDIA setting causing the behavior. I had no idea that the game and video player applications could be set to one resolution and the graphics card decide to output a completely different one.
a on October 1, 2007 6:19 PMI hope it's ok to use these tips to calibrate CRT display. Thank a lot!
LXj on October 2, 2007 1:06 AMPhotobox (a popular online photo lab in the UK) has a very sensible approach to simplified calibration.
They supply a "calibration print" with your first order and provide the same image on their website. Adjust your monitor so that the image on screen is as close as possible to the print and you have an instant "good enough" calibration.
See http://www.photobox.co.uk/quality.html for the image.
Graham Stewart on October 2, 2007 2:03 AMPreachin to the choir.
Mattkins on October 2, 2007 4:24 AMHi,
Output of MCE goes over VMR9 which boost the blacklevel a little higher then "really" black. So if you setup your black level with MCE you loose some grey-resolution in Games/Desktop-Apps.
So better set Black Level via any greyscale-test in a "non video" application (I use CRTAT) and after that adjust black for mce via the video-color correction in NVidia-Video-Settings. It's a little annoying becaus you have to switch between MCE and NCVidia Panel a lot to get it right, but I know no other way.
- Oliver
Oliver on October 2, 2007 8:32 AMHi,
Output of MCE goes over VMR9 which boost the blacklevel a little higher then "really" black. So if you setup your black level with MCE you loose some grey-resolution in Games/Desktop-Apps.
So better set Black Level via any greyscale-test in a "non video" application (I use CRTAT) and after that adjust black for mce via the video-color correction in NVidia-Video-Settings. It's a little annoying becaus you have to switch between MCE and NCVidia Panel a lot to get it right, but I know no other way.
- Oliver
Oliver on October 2, 2007 8:33 AM"it was a tweakers paradise"
I about spat out my food when I read that. Pure comedy. I love it.
Donn Felker on October 2, 2007 2:31 PMThe brightness theory is, the more expensive the LCD monitor is, the dimmer you can get. And photographers recommends view photos using dimmest setting to see the most out of a photos.
Since most LCD back panel are flourescent panel, it's difficult to simply tune down the power to make it looks dimmer. If you power up a flourescent panel with lower power, it will just flickers and becomes very unstable (try a dimmer switch on a flourscent lamp for a few seconds and you will know. But never try it for too long.)
AFAIK, EIZO monitor is particular good in this area. I bought one few years ago and another one last year as a dual monitor setup (same model, just before they discontinued it.) I know it's expensive but my eyes are even more expensive too. One of them said 4,000 hours and another one is like 1,000 hours now. And I can't spot any differences between them.
Compulim on October 2, 2007 4:35 PMI run dual display with two LCD panels. The video card I have has one DVI output and one VGA output, so one screen runs over DVI and the other over VGA. There is no discernable image quality between the two. Provided you are running at the native resolution of the LCD display, the screen should be able to determine the pixel clock and give you a virtually identical signal. Good quality VGA cables would make a difference, but most computer displays have very short runs (6 feet or less) where you are unlikely to encounter analog artifacts such as ghosting or ringing.
Tom A on October 3, 2007 1:04 PMI tend to run my MacBook at one notch of brightness above having the backlight off. For looking at photos or watching video sometimes I'll turn the brightness up, but for any amount of reading text it burns the eyes out of me, although I do have to turn it down slowly over a couple of minutes to let my eyes get used to it being darker. My 21" Trinitron at work is at about 1/4 brightness and 1/3 contrast and the highest colour temperature I could set (9300K with tweaks) so that whites aren't yellow.
John Ferguson on October 9, 2007 5:27 AMNeat demo of how background colors can affect your perception of colors-- mouse over the various colors in brackets [BLACK], [GRAY] etc to see in action.
http://www.displaycalibration.com/brightness_contrast.html
Jeff Atwood on October 16, 2007 10:26 PMPLEASE, EXPLAIN MORE DETAIL ABOUT YOUR SERVICING
| Content (c) 2009 Jeff Atwood. Logo image used with permission of the author. (c) 1993 Steven C. McConnell. All Rights Reserved. |
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