Wednesday, October 17, 2012

The Human Eye’s Subjective View of Color

Elements of a good photo include composition, color, and brightness. One of your jobs as a photographer is to capture the colors you see as intentionally as possible. Whether you intend to show the color exactly as you see it or you want to enhance the color by adjusting the color temperature, it is your job to understand your choices and intentionally compose your picture.
Unfortunately, human eyes and brains can’t be trusted to see colors objectively. Unless you can make side-by-side comparisons of your image on the screen, the photographic print, and the actual subject, it may be hard to tell in what ways the color shifts from one medium to another. Even when making side-by-side comparisons, it is nearly impossible to objectively measure what the differences are when using your eyes alone.

The subjective nature of visual perception should not necessarily be viewed as a handicap. If anything, it may be a blessing. Many challenges in photography come from the fact that the technology is so unforgivingly objective. A common example of this is the issue of white balance. Both film stocks and digital image sensors are designed to interpret white under specific conditions. Outdoor light (daylight) contains a lot more blue light than indoor (incandescent) light bulbs and candlelight. White objects in these different lighting conditions objectively look more blue (daylight), more red (incandescent), or more green (fluorescent), but the brain uses a number of psychological clues to infer that white objects are white, even if they are objectively different. A white car during sunset objectively looks quite orange, but if someone asks you what color the car is, you would reply with certainty that the car is white. That’s because you know the car is white even if it doesn’t look white at the moment. In the morning, the car has a bluish tint, and yet again, you would simply say it is white. Digital image sensors and film, on the other hand, record only what they objectively receive, and don’t interpret it. The auto white balance feature on many digital cameras measures the scene in the viewfinder and tells the camera to interpret the brightest point as white. This is important to know when switching between different lighting scenarios. Light and color can be objectively measured and characterized. The scientific analysis of light and color is necessary to build reliable, consistent photographic tools such as film, digital image sensors, displays, and printers. The goal is not necessarily to make all these devices capture or display colors the same way (although this would make things a lot easier), but to develop terminology and processes to objectively measure how these devices are different and adjust output accordingly, so that results match visual perception.

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