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Display Calibration 201: The Science Behind Tuning Your Monitor

Display Calibration 201: The Science Behind Tuning Your Monitor
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In Display Calibration 101: Step-By-Step With Datacolor's Spyder4Elite, we discussed one specific way to dial in your monitor; that is, to use the Spyder4Elite package to create a software look-up table (or LUT). This approach is both easy and relatively accessible, requiring very little knowledge of or training in the principles of display calibration and imaging science. 

But many readers commented that they wanted to learn more about adjusting their display's controls to achieve the same results. There are many tools available that can help you do this, and they'll be the subject of future articles. In fact, our next installment will cover the use of the CalPC package from SpectraCal. Today though, we’d like to lay a little groundwork so you know exactly what you’re in for.

There are two main reasons to calibrate any display. One is to match it to the other devices in the production chain like cameras and printers. In a photo studio, it’s crucial that the camera, printer, and monitor all conform to the same color and gamma profile. That way, what the photographer sees through the lens is what he sees on paper and on the screen. The second reason, the one we’ll be exploring here, is to match your display to a particular standard.

Why match a standard? It’s simple, really. Nearly every game or movie you view on your computer is mastered to the Rec. 709 video standard. This is nothing more than a specific set of parameters for color gamut, white point, and gamma. It covers other areas too, but for the purposes of display calibration, we only need to worry about those three. We’ll discuss what those parameters are and their importance in the first four sections. But calibrating your display to that standard ensures that you see exactly what the content creator saw.

There’s one more thing we’d like you to keep in mind as you move through the next few pages: the priorities of imaging science, a science of perception. How can one create a two-dimensional picture on a video display that naturally and accurately represents three-dimensional reality? Accepting the limitations of that display, we have to know how human beings perceive color, light, and detail.

To that end, imaging science as we know it is based on four elements. They are, in order of importance: dynamic range, color saturation, color accuracy, and resolution. Simply put, standards like Rec. 709 are intended to maximize those four elements. When all four are satisfied, you're looking at the most realistic image possible.

As we move on, we’ll go behind the scenes in the four major areas addressed by display calibration: levels, gamma, grayscale, and color. Understanding those principles means you’ll know exactly what’s happening when you move that brightness or RGB slider. And you’ll be able to identify your own display’s deficiencies and how to correct them. It's a wild ride, but we think you'll find it rewarding.

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  • 8 Hide
    expl0itfinder , October 13, 2013 9:31 PM
    Interesting article. Very detailed and well written. Kudos to the author.
  • -4 Hide
    MANOFKRYPTONAK , October 13, 2013 10:25 PM
    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?
  • -2 Hide
    yolosweg , October 13, 2013 10:37 PM
    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)
  • 0 Hide
    Vladimir83 , October 13, 2013 11:11 PM
    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.
  • 2 Hide
    rezzahd , October 14, 2013 8:08 AM
    Great display calibration guide. I would recommend this to anyone new to display calibration.
  • 1 Hide
    clonazepam , October 14, 2013 10:48 AM
    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. =)
  • 0 Hide
    ojas , October 14, 2013 11:19 AM
    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!
  • 0 Hide
    ojas , October 14, 2013 11:30 AM
    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.
  • 0 Hide
    ojas , October 14, 2013 11:56 AM
    Quote:
    Now we’ll make the color temp too warm; in other words, below D65.


    Shouldn't it be "above D65"? :/ 
  • 0 Hide
    gwolfman , October 14, 2013 1:04 PM
    Quote:
    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


    Quote:
    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.

  • 0 Hide
    Fokissed , October 14, 2013 1:08 PM
    Quote:
    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.
  • 1 Hide
    PhilFrisbie , October 14, 2013 1:10 PM
    Quote:
    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.
  • 0 Hide
    gwolfman , October 14, 2013 1:14 PM
    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).
  • 0 Hide
    ceberle , October 14, 2013 3:18 PM
    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-
  • 1 Hide
    ceberle , October 14, 2013 3:22 PM
    Quote:
    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-
  • 1 Hide
    Shankovich , October 14, 2013 5:50 PM
    Another great article to put in my references, this is why I love Tom's
  • 1 Hide
    jeffredo , October 15, 2013 1:33 AM
    I just broke down and invested in a Spyder 4 Elite colormeter.
  • 0 Hide
    kevith , October 15, 2013 3:32 AM
    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.
  • 0 Hide
    ojas , October 15, 2013 4:13 AM
    Quote:
    Quote:
    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


    Quote:
    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.



    Quote:
    Quote:
    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.


    Quote:
    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.
  • 0 Hide
    Christopher Shaffer , October 15, 2013 12:25 PM
    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".
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