How they see
How does a dragonfish see the world?
A secret far-red sniper scope
In the crushing dark of the deep sea, most animals see only blue, the last colour to reach those depths. The dragonfish is a rare exception with a lethal secret: some species produce and see red light, a private wavelength their prey are blind to. It effectively carries a sniper's scope, lighting up victims in a colour they never see coming.
See through their eyes
Human ≈ 60 cpd (20/10)
How sharp is a dragonfish's vision?
Its eyes resolve about 2 cycles per degree (20/300 (est.)), while a human reaches around 60 cpd (20/10). Its field of view spans about 180°.
How does a dragonfish see a human?
Its eyes resolve about 2 cycles per degree against your 60, so a face has to be roughly 30 times closer for it to pick out the detail you do. Your outline and your movement read clearly; your expression does not.
Colour comparison
How each colour shifts when seen through this animal's eyes, using the same colour model as the app. Tones a screen can't emit (such as ultraviolet) are shown as an approximation.
What colours can a dragonfish see?
Essentially monochromatic blue vision in the dark, plus a secret far-red channel used to light up prey without being seen.
Photoreceptors
Rod-dominated, blue-tuned; some species also detect far-red
Cone peak sensitivities
- Main (blue-green)530 nm
- Far-red (special)705 nm
How does a dragonfish see in the dark?
Extreme — adapted to the midnight zone.
How does a dragonfish's vision compare to a human's?
A dragonfish's detail is poor, perhaps 20/300 to your 20/20, and its world is essentially a single dim blue. For all that, it is exquisitely adapted to a darkness where you would see nothing, and a few species tap a red channel all their own.
What is special about a dragonfish's vision?
- Emits and sees far-red light invisible to prey
- Lives in near-total darkness
- Blue-tuned rods
What the research shows
The far-red story was built up over several papers. Partridge & Douglas (1995) reported that the dragonfish's suborbital photophore emits far-red light peaking around 705 nm. Microspectrophotometry then showed that the genera differ: Aristostomias carries at least three long-shifted visual pigments near 515, 550 and 590 nm, while Malacosteus has only two, near 520 and 540 nm, and lacks the longest. In its place, Malacosteus uses a photosensitizer derived from bacteriochlorophyll, obtained from the copepods it eats, to extend its sensitivity into the far red, the finding Douglas et al. (1998) published as 'Dragon fish see using chlorophyll'.
The page condenses this into one main blue-green peak at 530 nm plus the 705 nm emission, a simplification of pigment sets that vary by genus. Spatial detail has not been measured at all: the notes estimate 1 to 3 cycles per degree for a small eye working in near-total darkness close to single-photon limits, and the simulation uses 2 cpd. Here the limit of a screen is absolute. A phone camera's infrared-cut filter blocks light near 705 nm and a display has no far-red primary, so the wavelength this fish relies on can only be described, never captured or shown.
Guides: Are animals colour blind? · Which animal has the best eyesight? · All guides
Scientific sources
- Douglas et al. (1998)
- Partridge & Douglas (1995)
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