QUESTION: I know that concealment is top priority, but up here in Maine most hunters I know don't use a blind or tree stands and we're decked out in florescent orange. How well does a deer see and what colors do they actually see? -- Mike P.
ANSWER: Entire articles have been written about deer vision; some even by me! I’ll try to give you the Reader’s Digest version.
Mammals have two types of photoreceptors: rods and cones. In very basic terms, the rods allow us to see different shades of dark and light, while cones allow us to see color. Deer have more rods than humans, which allows them to see better in low light. They also have something called a tapetum on the back of their eye that reflects light - thus the glowing reflection of a deer’s eyes in your headlights - further enhancing their night/low light vision.
Deer vision researchers found only two classes of cones (color receptors) in deer, as opposed to three in humans. Unlike the trichromatic (three-color) vision of humans, deer vision is most sensitive to short wavelength (blue-violet) and middle-wavelength light (green-yellow). Furthermore, their lenses lack yellow pigment of the human eye that acts to filter out ultraviolet light almost completely, and absorbs it strongly in the violet and blue regions. As a result, their sensitivity to short wavelength light (blue and violet) is much higher than that of humans. Sensitivity is lowest in the middle to long wavelength light (yellow-green, green, yellow, orange, and red). To them, orange and red appear only as different shades of gray, which is why they aren't particularly alarmed by blaze orange. More often it’s the solid human form, rather than the color that catches their eyes.
Bear in mind also there are two ways to make blaze orange clothing. One is by combining red and yellow. The other is by combining yellow and magenta - the latter of which is in the peak sensitivity range of a deer’s visual spectrum, and thus will glow in a deer’s eyes. Also consider that most conventional laundry detergents and many of the color dyes used on camouflage clothing manufactured overseas contain so-called blueing, brightening or whitening agents. What they do is collect light energy from a wide range of wavelengths, and re-radiate it in a powerful peak at a range of about 440 nanometers - near maximum sensitivity of a deer.
In the dim light of dawn and dusk, these brightening agents can make your clothes glow like a neon sign in the eyes of a deer. You can overcome this by applying a product called U-V Killer to your apparel. From that point on, wash only in a scent-free, brightener-free soap designed for hunting clothes and you should be okay.