We’ve established that dynamic range is the most important element in image quality. Just like audio, the greater the difference between the extremes (soft and loud, light and dark), the greater the realism and sense of depth. And in a rare bit of good fortune, this is the one thing a user can achieve with a monitor that doesn’t require a meter or fancy software! What we’re talking about are black and white levels, or, as they’re more commonly known, brightness and contrast.
At some point in history, a not-so-clever television engineer decided that the controls affecting dynamic range should be called brightness and contrast rather than black level and white level. This has created confusion as to what these adjustments are actually for. It’s actually quite simple, though. Brightness is black level and contrast is white level.
Now, what are we doing when we change those controls? Black level/brightness refers to the minimum level of light a display will produce. White level refers to the maximum level of light. Obviously, by minimizing black and maximizing white, you'll achieve the highest contrast ratio and the greatest dynamic range possible for a given display. The trick is to set the levels properly, while retaining all of the image's detail.
To illustrate the importance of setting black and white levels correctly, let’s check out an actual photograph. We modified the original in Photoshop by using the Levels dialog to manipulate the black and white levels. This is functionally the same as adjusting the brightness and contrast controls on your monitor. No adjustments were made to color.
Here’s a shot of singer Gavin Rossdale performing with Bush.

This is a pretty detailed photograph. You can clearly see the definition in his arms, his hair, and his jeans. Plus you can see the audience far in the background. And check out the subtle outline of his right hand against the guitar’s body.
Here’s the histogram.

Nearly the entire brightness range is represented, except for a few steps at the dark end. And there are one or two steps at the bright end that get crushed. This image is straight from the camera with no post-processing.
Here’s the same shot with the black level set too low.

The audience and Gavin’s hair get obliterated. His right hand now blends into the guitar’s pick guard. And his jeans have far fewer wrinkles than before. This is what we mean when we use the term crush or clip in reference to black. The darkest information is crushed together and shadow detail is lost. Where there were perhaps 50 gradations of black, there is now only one. While an artist may purposely modify an image like this for extra impact, the fact is that some of the original information was lost.
Now let’s see what happens when you set white level too high.

Gavin’s face and right arm turn into formless white shapes, and we lose the dimension we saw in the original. The many shades of white that created detail in his face are now blended together. Since the audience in the background is also brighter, the sense of depth is significantly reduced. It’s harder to tell just how far away they are.
Here’s the same photo with the black level set too high.

You can still see the detail, but now there’s a hazy look to the photo, as if a filter was put in place. Any sense of image depth is drastically reduced.
Our final example shows the effect of setting the white level too low.

Again, the detail is all there, but the photo looks dim and underexposed. This and the previous image retain all of their detail. However, by reducing the dynamic range, the vibrancy and impact are significantly lower.
We’ll show you how easy it is to fix these problems with a couple of test patterns you can download from the Internet. Setting black level and white level properly doesn’t require instruments or software. And it’s one of the best things you can do to improve your monitor’s image. By maximizing dynamic range, you’re well on your way to better pictures!
To fully take advantage of a display’s dynamic range, we also need to understand what’s happening to the points in between black and white. This is where the discussion turns toward gamma.
- The Two Reasons To Calibrate Your Monitor
- Levels: The Key To Contrast And Detail
- Gamma: The Key To Maximum Image Depth
- Grayscale: Why White Is The Color Of Everything
- Gamut: What Color Is Your Monitor?
- Application: How To Adjust Levels
- Application: How To Adjust Gamma
- Application: How To Adjust Color Temperature
- Application: How To Adjust Color
- Calibrate Your Monitor For A Better Picture
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.
I love these articles. =)
Seems to be an interesting read so far, and I've really wanted to read an article like this, so thanks in advance!
It's written the other (incorrect?) way around in the article, i think.
Shouldn't it be "above D65"?
It's written the other (incorrect?) way around in the article, i think.
http://www.cambridgeincolour.com/tutorials/gamma-correction.htm
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.
Shouldn't it be "above D65"?
Warm (reddish) colors are below 6500K, whereas cool (bluish) colors are above 6500K.
Try installing a full featured driver from your video hardware manufacturer.
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).
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-
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-
It's written the other (incorrect?) way around in the article, i think.
http://www.cambridgeincolour.com/tutorials/gamma-correction.htm
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.
Shouldn't it be "above D65"?
Warm (reddish) colors are below 6500K, whereas cool (bluish) colors are above 6500K.
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.
That would be very useful, along with some recommendations of affordable "meters".