Hermann grid illusion / nobody knows anything

June 28, 2008

Illusion: In your peripheral vision, you may see dark spots where the lines intersect. If you look at an intersection directly, you can see that there is actually no dark spot.
The textbook explanation for this effect has to do with the ganglion cells in our eyes. In the center area of our [...]

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Chromaticity versus chrominance

June 23, 2008

Color spaces can generally be classified as chromaticity or chrominance based. Both are different styles of defining color. Chromaticity is “color” defined independent of luminance (or the equivalent of luminance in a particular color space). Suppose you used a neutral density filter on a camera or changed the intensity of the lighting. The [...]

Filed under: color correction, color science | Comments (4)

Is LAB useful for color correction?

June 23, 2008

For color correction, it might seem sensible to use a perceptually uniform color space. CIE L*a*b* is one such color space that is designed to be perceptually uniform.
In the context of LAB, perceptual uniformity means that the ability to tell two shades apart is uniform. This is usually measured in just [...]

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Surround Effects (Part 2)

June 23, 2008

One area where surround effects make a big difference is when evaluating the black level on LCD monitors. Almost all LCD monitors cannot reproduce true black and have a raised black level. In a dark room, they will have a “glow in the dark” appearance to them. The image below shows the [...]

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Surround Effects (Part 1)

June 22, 2008

One of the factors that affect the perception of an image is the content of the area surrounding it. In the example below, the center patches of the color have the same value (128 128 128 RGB) yet the left patch appears to be lighter than the one on the right.

Adding [...]

Filed under: color science, monitoring, visual illusions | Comments (1)