What colors can deer see?

Jacobs and colleagues (1994) measured the retinas of white-tailed deer and fallow deer with electroretinogram flicker photometry. Both species have a short-wave cone with its peak in the region of 450–460 nm. The second cone peaks near 537 nm in white-tailed deer and at 542 nm on average in fallow deer. The rod pigment peaks near 497 nm. The authors conclude that deer have the retinal basis for dichromatic color vision. Human eyes have three cone types, peaking at about 420, 534 and 563 nm (Bowmaker and Dartnall, 1980).

The chart uses 455 nm for the short-wave cone: the middle of the 450–460 nm region the study gives, not a single measured value.

With one short-wave and one long-wave cone, colors that differ for us mainly in how red or green they are give a deer much the same signal. The table runs a few hunting-season pairs through the same model as the simulator and gives the color difference (ΔE 2000) for a person and for the deer model: the smaller the number, the harder the pair is to tell apart. On the scale we use across this site, below 3 is a close match, 6 or more is a visibly different color, and 10 or more is clearly different. The swatches are illustrative colors, not measured fabrics, and the numbers depend on the shades: against darker forest greens the same jacket gives the deer model ΔE 20 or more, almost all of it lightness.

The model changes color, and with it how light some colors look; outlines stay, but fine detail is blurred (see below). This page is about color vision and gives no advice on hunting or safety clothing.

The simulator is built from the deer's own cone peaks (455 and 537 nm). For each color it estimates how strongly it would excite each of the two cones, using the pigment template of Govardovskii and colleagues (2000) and daylight (CIE D65), and shows a color that excites them in the same way. The cone signals weigh the light by its energy; a cone counts photons, and weighting by photon count instead would shift some shown colors slightly, by up to about 15 of 255 in one color channel by our check. The shown colors lie on a yellow–blue axis plus lightness, the same plane that Viénot, Brettel and Mollon (1999) use for people with two cones, so colors that give the deer the same pair of cone signals come out identical. It is an approximation: the eye's lens is left out, each color's spectrum is a guess from its screen color, and the picture is blurred to the animal's visual acuity, as explained below. Everything runs on your device: the camera picture, photos and videos are not uploaded.

Watson and colleagues (2022) trained three adult female white-tailed deer by operant conditioning and estimated their spatial resolution at between four and six cycles per degree. The simulator blurs the picture to 5 cycles per degree, the middle of that range. We read only the summary (abstract) of the paper.

How the blur is made: the simulator follows AcuityView, the method of Caves and Johnsen (2018). Fine detail is faded along a bell-shaped curve that leaves about 3% of the contrast at the animal's acuity limit, and coarse shapes and colors stay. A picture does not say how wide the scene was, so the simulator assumes that the long side of the picture covers about 70°, the view of a typical phone's main camera (the iPhone 16 main camera is 26 mm in 35 mm terms, about 69° across). If you zoomed in or cropped, the scene was narrower and the animal would see it blurrier than shown. The blur stands for the sharpest part of the eye only; the rest of the animal's view is not modelled.