How dolphins see

Fasick and colleagues (1998) made the bottlenose dolphin's visual pigments in the lab from its genes. The rod pigment peaks at 488 nm and the only cone pigment at 524 nm (green). The dolphin still has a gene for a short-wave (blue) cone pigment, but it is broken and not used, so the dolphin lacks even the two-cone color vision of most land mammals.

Behavior agrees. In a test summarized by Herman (2010), a dolphin could not reliably tell blue, green and red lights apart once their brightness was matched (Madsen and Herman, 1980).

Not everyone is sure that dolphins see no color at all: some researchers have suggested that a dolphin might tell some colors apart by comparing its one cone with its rods (as summarized by Meredith and colleagues, 2013). The simulator shows daylight vision through the cone alone.

With one cone, two colors look different only if that cone finds one brighter than the other. The simulator turns each color into a gray as bright as the dolphin's 524 nm cone finds it. That cone responds less to red than our red-sensitive cone does, so red comes out dark gray.

The table runs a few everyday pairs through the same model and gives the color difference (ΔE 2000) for a person and for the dolphin 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.

For each color the simulator estimates how strongly the dolphin's cone (524 nm) would respond, using the pigment template of Govardovskii and colleagues (2000) and daylight (CIE D65), and shows a gray of the same brightness; white and grays stay as they are. The cone signal weighs the light by its energy; weighting by photon count instead would change some grays by up to 8 of 255 in our check. It is an approximation: the eye's lens is left out, the light is daylight in air, not under water, and each color's spectrum is a guess from its screen color. Everything runs on your device: the camera picture, photos and videos are not uploaded.

Herman and colleagues (1975) found that in bright daylight a bottlenose dolphin resolved striped patterns about equally well in air and under water. Its double slit-shaped pupil makes up for the strong short-sightedness its eye has in air. In air, sharpness improved with viewing distance; under water, it improved as the patterns came closer.

Tomonaga and colleagues (2014), citing that study, give the finest detail as 12.6 minutes of arc at a distance of 2.5 m; a review by Bauer and colleagues (2020) gives the same study's value in air as 12.5. By our arithmetic that is about 2.4 cycles per degree (one cycle is a dark and a light stripe). Under water the limit was finer: 8.5 minutes of arc in that review, 8.2 in a review by Cook and colleagues (2025), about 3.5 to 3.7 cycles per degree by our arithmetic. The simulator uses the in-air 2.4, because a photo is taken in air. We have not read these numbers in the 1975 paper itself. People in a two-choice stripe test resolved 32.1 to 44.2 (Lind and colleagues, 2017), more than ten times finer than the in-air value.

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 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.