Display Calibration 201: The Science Behind Tuning Your Monitor

Gamut: What Color Is Your Monitor?

If you read the explanations of color gamut in our monitor reviews, or in Display Calibration 101: Step-By-Step With Datacolor's Spyder4Elite, then you know that color gamut is another standard by which displays are matched to each other, as well as to cameras and printers. While it is possible to have a screen with a built-in color management system, it’s far more common to create a look-up table, called an ICC profile, that reconciles differences between a monitor’s actual color gamut and the target values.

Below we have a different representation of the CIE chart.

We chose this one because it shows the two gamuts currently available on computer monitors: Adobe RGB 1998 and sRGB. As you can see in the graphics, they are subsets of the full chart, which portrays the spectrum of color visible to the human eye. How close a display comes to these gamuts is a very important part of our testing.

There are other standards besides these two. The most common one is Rec. 709, which is used by high-definition televisions and projectors. Why don’t we show it on the chart? Because it’s identical to sRGB. They are indeed interchangeable. The other standard we’ll mention briefly is Rec. 2020, which is still a proposed spec and not currently in use on any production displays.

This is the proposed color gamut for ultra-high definition screens at both 4K and 8K resolutions. When this gamut is actually used in a monitor, you’ll need appropriate content to match it. And that is unlikely to happen without major upgrades in optical disc storage capacity and bandwidth, since it requires a minimum of 30 bits per pixel to encode.

How does this apply to our discussion? All fixed-pixel displays use three primary colors, red, green, and blue, to display an image. In the case of an eight-bit panel, 2563 gives us a possible 16,777,216 colors. Obviously, the positions of those primaries on the CIE chart are of paramount importance. Assuming that the camera used conforms to the standard, the only way we’ll see the same image is if our monitor conforms to the same standard.

That’s simple enough to understand, but what about the secondary colors?

In between the primary color points are the secondary ones: cyan, magenta, yellow. These are created by mixing two of the primaries in a particular ratio. The technical term is phasing and it’s important that a display does this correctly. A screen can have spot-on primaries, however, if the secondaries are off, visible color errors will result. Previously, we saw that adjusting the white point can help align secondaries. And most of the time, this is the only thing we can do to improve a display’s color accuracy.

Now we’ll get into some actual application of all this science. We’re going to explain just how we calibrate a monitor using its built-in controls only. This is exactly what we do for our reviews.

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26 comments
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  • expl0itfinder
    Interesting article. Very detailed and well written. Kudos to the author.
  • MANOFKRYPTONAK
    For TVs CNET posts the color levels they use to test each TVs picture by model. They also give great advice on how to adjust too! I used there settings with my 50" vizio and could not be happier. Don't get me wrong loved this article, but you can never get too much info, am I right?
  • yolosweg
    I've adjusted the gamma on my laptop but it keeps reseting. Does anyone know how to fix this? (I used the default windows program btw)
  • Vladimir83
    Fantastic article.....TomsHardware style!
    I have no idea how my monitor was off until i saw the patterns ;)
    Now perfectly set for brightness/contrast:first,third,and fourth pattern(although on this i notice cliping on the blue).
    However second pattern couldn't set it right.Darkest bar which should be almost cliping to the background is too "black",and the next "12" bar is more closely match to the background in colour.
    Any thoughts someone? I use Philips 227Eqha IPS monitor.
  • rezzahd
    Great display calibration guide. I would recommend this to anyone new to display calibration.
  • clonazepam
    Every time I took a support call for pro graphics products, and it centered around getting accurate color, I started off with "Color is a 3-dimensional space..." It was just my way of saying we might be here for awhile.

    I love these articles. =)
  • ojas
    Second page, second last photo, article should say that you've set the black level too low, not too high.

    Seems to be an interesting read so far, and I've really wanted to read an article like this, so thanks in advance!
  • ojas
    Doesn't the first picture of Gavin on the 3rd page have low gamma and the second bright one is where the gamma is too high?

    It's written the other (incorrect?) way around in the article, i think.
  • ojas
    Quote:
    Now we’ll make the color temp too warm; in other words, below D65.


    Shouldn't it be "above D65"? :/
  • gwolfman
    463569 said:
    Doesn't the first picture of Gavin on the 3rd page have low gamma and the second bright one is where the gamma is too high? It's written the other (incorrect?) way around in the article, i think.
    It's opposite. Lower gamma makes the dark areas of an image brighter, hence the entire picture looks brighter. Higher gamma makes the lighter areas darker (i.e., it takes a lot brighter white in the image data to actually be displayed white). Check here for a great tutorial on gamma, especially the section titled "Display Gamma."
    http://www.cambridgeincolour.com/tutorials/gamma-correction.htm


    463569 said:
    Quote:
    Now we’ll make the color temp too warm; in other words, below D65.
    Shouldn't it be "above D65"? :/

    That's incorrect. It actually works backwards/opposite from what one might think. Color temperature originates from the color a flame radiates in relation to the temperature at which it burns. Think back to grade school and playing with the Bunsen burner... the hottest part of the flame (i.e., higher Kelvin) is in the darkest blues, not the reds (i.e, lower temperature/Kelvin). This simple picture helps explain the difference.

  • Fokissed
    463569 said:
    Quote:
    Now we’ll make the color temp too warm; in other words, below D65.
    Shouldn't it be "above D65"? :/


    Warm (reddish) colors are below 6500K, whereas cool (bluish) colors are above 6500K.
  • PhilFrisbie
    1446217 said:
    I've adjusted the gamma on my laptop but it keeps reseting. Does anyone know how to fix this? (I used the default windows program btw)


    Try installing a full featured driver from your video hardware manufacturer.
  • gwolfman
    The author of the article stated:
    Quote:
    We always measure color gamut and luminance in our monitor reviews, even though those parameters are not adjustable in most cases.

    But don't most monitors have a "backlight" option which changes how bright the image without adjusting the contrast & brightness? This can used to effectively adjust liminance, but at superficial global adjustment level rather than a granular control. None the less, one can then put preference on the brighter or darker end depending on their use case(s).
  • ceberle
    Thanks for your questions about gamma and color temperature. It seems counterintuitive to say that lower gamma produces higher brightness but that is indeed the case. The lower the value, the higher the brightness.

    Grayscale can be confusing too. As the temperature gets lower, the color is said to get warmer.

    Ojas, the photo on page 2 showing a higher black level is correct. As you raise the black level, blacks get brighter and become more gray.

    -Christian-
  • ceberle
    118795 said:
    The author of the article stated:
    Quote:
    We always measure color gamut and luminance in our monitor reviews, even though those parameters are not adjustable in most cases.
    But don't most monitors have a "backlight" option which changes how bright the image without adjusting the contrast & brightness? This can used to effectively adjust liminance, but at superficial global adjustment level rather than a granular control. None the less, one can then put preference on the brighter or darker end depending on their use case(s).


    Unfortunately, very few monitors have separate backlight and brightness controls. None of the screens we've covered this year (16 including reviews not published yet) have a backlight control. This kind of thing is common on HDTVs but not computer monitors and that is a shame. With brighter screens, it's really nice to be able to move the dynamic range up or down to get better blacks or brighter whites, depending on application.

    -Christian-
  • Shankovich
    Another great article to put in my references, this is why I love Tom's
  • jeffredo
    I just broke down and invested in a Spyder 4 Elite colormeter.
  • kevith
    My monitor looks the same no matter what of this I try. And the conclusion is, as in the case of every "adjust-your-monitor-in-an-amazing-small-number-of-steps" article I ever read: Go buy the hardware thingy or forget it.
  • ojas
    118795 said:
    463569 said:
    Doesn't the first picture of Gavin on the 3rd page have low gamma and the second bright one is where the gamma is too high? It's written the other (incorrect?) way around in the article, i think.
    It's opposite. Lower gamma makes the dark areas of an image brighter, hence the entire picture looks brighter. Higher gamma makes the darker areas even darker (i.e., it takes a lot brighter white in the image data to actually be displayed white). Check here for a great tutorial on gamma, especially the section titled "Display Gamma." http://www.cambridgeincolour.com/tutorials/gamma-correction.htm
    463569 said:
    Quote:
    Now we’ll make the color temp too warm; in other words, below D65.
    Shouldn't it be "above D65"? :/
    That's incorrect. It actually works backwards/opposite from what one might think. Color temperature originates from the color a flame radiates in relation to the temperature at which it burns. Think back to grade school and playing with the Bunsen burner... the hottest part of the flame (i.e., higher Kelvin) is in the darkest blues, not the reds (i.e, lower temperature/Kelvin). This simple picture helps explain the difference.


    339404 said:
    463569 said:
    Quote:
    Now we’ll make the color temp too warm; in other words, below D65.
    Shouldn't it be "above D65"? :/
    Warm (reddish) colors are below 6500K, whereas cool (bluish) colors are above 6500K.


    1025177 said:
    Thanks for your questions about gamma and color temperature. It seems counterintuitive to say that lower gamma produces higher brightness but that is indeed the case. The lower the value, the higher the brightness. Grayscale can be confusing too. As the temperature gets lower, the color is said to get warmer. Ojas, the photo on page 2 showing a higher black level is correct. As you raise the black level, blacks get brighter and become more gray. -Christian-

    Thanks for clarifying that! I even changed gamma on my monitor to see what happens before i posted, i guess i misinterpreted what was happening.
  • Christopher Shaffer
    This is all very interesting and I was excited for a basic how-to until you suddenly said "now get out your meter" but didn't tell me what kind of meter and didn't give me a "parts list" that I'll need to follow your guide.

    That would be very useful, along with some recommendations of affordable "meters".
  • Christopher Shaffer
    Actually, my above comment being said, I think it would be useful for us gamers to have a recommended list of free software to use as a basic reference for calibration.

    I doubt most gamers will spend $200 on calibration meters and software if our profession doesn't warrant this obsessive level of color accuracy, but a nice guide and suggested software to go along with it would be very nice.

    After all, accurate colors in BF4 are nice, too.
  • Christopher Shaffer
    Actually, my above comment being said, I think it would be useful for us gamers to have a recommended list of free software to use as a basic reference for calibration.

    I doubt most gamers will spend $200 on calibration meters and software if our profession doesn't warrant this obsessive level of color accuracy, but a nice guide and suggested software to go along with it would be very nice.

    After all, accurate colors in BF4 are nice, too.
  • kulmnar
    Hmmm...this article has one major omission, in dark environments, the brightness (especially of LED/LCD displays) needs to be artificially lowered...I don't like making my eyes sore just so that I can conform to a standard!
  • gwolfman
    629156 said:
    Hmmm...this article has one major omission, in dark environments, the brightness (especially of LED/LCD displays) needs to be artificially lowered...I don't like making my eyes sore just so that I can conform to a standard!
    The brightness level isn't actually part of any of the standards mentioned! I mean there's recommendations, but it's all based off of viewing environment. For example, the author mentioned 200 nits/lumens for the brightness, but that's merely a recommendation for bright office environments. The Society of Motion Picture and Television Engineers (SMPTE) standard specifies a 55 nit/lumen screen for movie theaters, which is quite low. However, you have to keep in mind how dark it is in there and how well controlled the lighting is and I'm sure their standard also specifies a specific level of ambient lighting. (Additionally, we aren't attempting to follow their standard.)

    A lot of color-critical work is performed in rooms with controlled lighting, so monitors are calibrated anywhere from 80-120 nits/lumens. They even incorporate light meters into many of the calibration meters so they can measure the ambient light and calculate the best brightness of the screen to match the environment.

    So basically to answer your question, you can pick whatever you want. As a side note, some monitors perform better or worse depending on how bright the screen is, so you might gain/loose detail/performance depending on the particular monitor.