Calibrating your LCD for Better Results

When you’re designing interfaces or adjusting your color photos, you must be able to rely on your computer screen for color accuracy. As you may know, I am an amateur photographer and, consequently, I often post-process my pictures to make them actually presentable. However, I would never do such a thing on my Dell laptop because the matte LCD screen is… well, let’s say not up to the task. Red ends up somewhat salmony, so I really can’t use it to do any kind of decent photo processing. My old Vaio, on the other hand, with its glossy display renders stunningly deep and vibrant colors.

smpte-color-bars

But just how much can you trust your display? Can you adjust it without buying the rather expensive color calibration gizmos yet have decent results? In this week’s post, I present my techniques (meaning: tricks) to calibrate LCD (most also apply to CRT) screens.

All the images used in this post can be found in most resolution at the very end of the post. Select the ZIP archives that correspond to the screen(s) you are using. Be sure to read the license.

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If you have a VGA cable linking your computer to your LCD screen (like many people) you may get sub-optimal results. The VGA image signal is analog and by definition susceptible to noise, but most importantly, it is little more than a TV signal. That is, even if your computer outputs a resolution of, say, 1280×1024, the VGA signal can only convey the number of lines. Lines of pixels can be aligned with the physical lines on the LCD, and so vertical positioning is precise. Horizontal pixel positioning is another story: the VGA signal does not provide a horizontal pixel clock, so the LCD cannot always map an image pixel with a physical screen pixel, leading to blurry or noisy images.

The solution? Ideally use a digital connector such as DVI or HDMI. If you can’t, or won’t, do the following. Provide your LCD with a pattern that will allow it to adapt to the current resolution and estimate the horizontal pixel clock accurately. Use the following bitmap , display it at 100% so that one image pixel maps exactly to one LCD pixel, full screen, if possible. Hit the auto-adjust button on your LCD.

The Pixel Clock Test Image

The Pixel Clock Test Image

Normally, after a short flickering, you should see the noise greatly reduced and edges of fonts and windows should appear much sharper than before.

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If you adjusted the image quality, it’s now time to adjust contrast and brightness. First, you must recreate the lighting conditions with which you work most often. If you work during the day in broad daylight, adjust your monitor during the day. If, like me, you work at home in the evening, wait until sundown and recreate your usual lighting conditions: a mood lamp here, a desk lamp there… That’s far from whimsical; you will need to adjust your monitor to the usual lighting conditions for better results.

OK, once that’s done, you will adjust the brightness and contrast of your monitor. For the dark end of the spectrum, you’ll use this image full screen:

Dark Color Adjustment (colors exaggerated)

Dark Color Adjustment (colors exaggerated)

You will adjust the brightness and contrast so that if you lower the brightness just one more step down, the color rectangles disappear. The best setting is so that they are just barely visible. At the other end of the spectrum, you will adjust brightness down so that all six rectangles in the following picture appear distinctly.

Bright Color Adjustment (colors exaggerated)

Bright Color Adjustment (colors exaggerated)

Now, as brightness is set, you will adjust contrast so that the following image shows the most progressive color gradients as possible. You may also adjust saturation to make the colors punchier or, on the contrary, more muted. This complemented by the color temperature setting on your monitor. They usually offer a number of settings, like 6500K, 9300K, or even colors profiles such as sRGB. sRGB is a “standard colorspace” developped jointly by Microsoft and HP, and is recognized by devices like printers. 6500K is the usual “cool” setting. However, settings as high as 9300K give a bluish tint to colors, so you probably want to avoid this. Select either 6500K or sRGB (both are close in terms of color temperature but the gammas differ greatly).

Constrast and Saturation Adjustment

Constrast and Saturation Adjustment

You may need to iterate all three adjustments (brightness, constrast, saturation) until you get it just right.

The All-in-One Test Image

The All-in-One Test Image

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The color band test also serves to assess the number of colors your screen is capable of displaying. Even if your video card settings say that your are in 24 bits (True Color or “millions of colors”), it doesn’t mean that your screen is physically capable of displaying so many distinct colors. Indeed, even Apple got caught in a scheme selling monitors as capable of “millions of colors” as they call it but in fact the screens where only capable of a mere 256K colors (18 bits). So if your screen looks like this:

Effect of Lower Color Resolution (effect exaggerated)

Effect of Lower Color Resolution (effect exaggerated)

it is likely that you’re not having a true 24 bits display. This is fairly common in lower-end laptops, cell phones, car DVD players, etc.

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So now you’re all setup for better photo editing or whatever you’re doing that necessitate color (brightness, contrast, saturation) precision. However, let me be clear: this is by no mean a replacement for professional color management. For this, you’ll need extra software for colors profiles and very likely a color calibration probe of the type that you stick to your screen an that estimates its color gamut in order to compute the optimal color profile.

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Files

To download the ZIP archive that contains the resolutions for your (s), click one of the following links. All images are released under GPL v2.0. What does the GPL change for you? Not much! You can modify the but you must redistribute (that is, make available) the derived work with attribution.

3 Responses to Calibrating your LCD for Better Results

  1. […] Laptop Colors: Why? In Calibrating your LCD for Better Results I presented a few techniques to adjust your LCD so that you get better colors, even though […]

  2. […] If it’s a table-top LCD screen, there are a number of settings one can adjust and normally one arrives at a moderately good result without too much effort. That is, gray color appears as gray, good contrast, and full dynamic range. I’ve explained how to do this without the pain before. […]

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