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"White-tailed deer would be expected to have dichromatic color vision". Human dichromats called protanopes also lack the red cone function. A human with one dichromatic eye (blue/green cones) and one trichromatic eye (blue/green/red cones) can tell us the difference in color perception. They see blue as blue and the rest of the spectrum from green to red as the color yellow, with their dichromatic eye. Therefore, if blaze orange or most green/brown camouflage is without brightener effect, it is all yellow. It will all blend in well in a world of green leaves, yellow grass, and brown trees, because they too are all yellow.

Now consider what effect U-V brighteners would have on these garments that appear yellow in a yellow world. Blue flags? Yes, but only on blue, white, light shades of gray, and other colors that have some blue content. Other colors will simply appear brighter and whiter much as intended for humans. In low light the problem is even greater. Many subtle differences in physiology make the deer far more sensitive to dim light-especially shorter wavelengths. They switch to black and white rod vision as humans do but can detect light 1000X below our threshold in the blue and U-V wavelengths

COLOR VISION

The ability to see color is an important aspect of human vision. Color differences often allow us to easily identify objects from their backgrounds that would otherwise be invisible. For example, at a distance, ripe red tomatoes on the vine are much more easily seen among the leaves than unripe green ones. Humans are able to see color because of three different types of cone photoreceptor cells in the retinas of their eyes. One cone type is most sensitive to short wavelength (blue) lights a second is most sensitive to middle wavelengths (green) and a third is most sensitive to long wavelength (red) lights. The three different cone types are the basis for what has been termed trichromatic (literally three-color) vision in humans. It should be noted as an aside that the majority of the cone photoreceptors in the human retina are the long-wavelength sensitive type, the middle wavelength sensitive type are the next most common, and the short wavelength sensitive are rare-only about 10% of the cones. The blue sensitive cones are important for color vision, but because of their small number they provide little or no over-all sensitivity to short wavelength light. Scientists have studied color vision capacities in a number of animals. Among mammals, only primates (monkeys and apes) have been found to have trichromatic color vision like that of humans. However, a number of other mammals have color vision that is based on only two different cone types; this is dichromatic (two-color) vision. This simplified type of color vision seems to be common among mammals and has been observed in carnivores (e.g. dogs and cats) and ungulates (hoofed mammals). Although vision is predominantly based on rods in these animals (more than 90 percent of the total photoreceptors in their eyes are rods giving them excellent night vision), they have enough cones to provide color vision. Obviously color vision based on only two different cone types is not going to be as good as human color vision that is based on three types. The deficiency in dichromatic color vision is in the ability to discriminate among the colors of objects that reflect light in the middle to long wavelengths, i.e. green, yellow, brown, orange, and red. The ungulates and carnivores with color vision based on only short wavelength sensitive cones and long wavelength sensitive cones, would find these colors difficult or impossible to distinguish. However, for these animals, blue, violet and near ultraviolet (which is invisible to us because it is blocked by the lens) stand out from the other colors. The colors of earthly objects are mostly browns, tans, greens and yellows. To an animal with dichromatic color vision, a sportsman wearing garments that strongly reflect short wavelength light would stand out against these backgrounds like a ripe red tomato on a green vine.

Sincerely Yours, Jay Neitz, pH. D . Vision Scientist