color1

Accurate Color ?
(Well maybe semi-accurate color)

There are many fundamental problems with displaying accurate color representations on a CRT tube. The "real world" is made up of reflected light, while the CRT creates images via transmitted light. Add to this, the fact, that the human eye has a range of color reception that is unlike film or the electronic response of a video camera, and color matching can become a real challenge.

Color prints created from negatives require "color balance" or the addition of filters during the printing process to balance the enlarger's light color (sometimes called color temperature), and remove the film's mask color (that orangish color you see at the edge of color negatives (Figure 1.)). Essentially the idea is to reproduce the same color temperature (minus the film mask color) that was used when capturing the image. Slides work in a similar way, if an outdoor slide was taken with full sunlight, then using a projector bulb (with a similar color temperature) closely reproduces the correct image coloration when the slide is projected.

Figure 1.

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Figure 3.

Figure 4.

When working with video capture, and reproduction via CRT things are a little different, as it is difficult to correlate electronic parameters, and relate them to the precise color temperature from an original. In this process the color image is digitized to an electronic signal, assigned a set of color values, and then saved. When redisplayed the process is reversed, but also subject to the electronics of the display device. Viewing the same image on a number of different monitors is likely to result in a number of different interpretations. Due to different gamma values.

Most video systems use a "white balance" to aid in overcoming color problems created by adverse lighting conditions. The color balance assumes that under normal conditions, that if a white object can be made to look white, then the remaining colors will be accurate too. If the original lighting is not close to the proper color temperature (typically daylight), the "white balance" may reproduce white at the expense of other hues.

Another way of looking at this, is suppose there is a white crystal (figure 2.) in an image, and we color it light red (Figure 3.). If we use the crystal to do a white color balance (eyedropper sampling in Figure 3.), the camera's electronics will make the crystal white by over compensating for red. To compensate for the red, the image must be corrected with additional green and cyan, thus other items in the picture take on a green-cyan shade (Figure 4.), while the crystal becomes white with gray shadows. White balance only works well when there is a truly white item in the image.

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