In the film Blade Runner (1982), Rick Deckard hunts realistic androids called replicants.

According to Jordan Cronenweth, Blade Runner's (genius) director of photography,

One of the identifying characteristics of replicants is a strange glowing quality in their eyes

Nevertheless, the plot of Blade Runner has Deckard identify the replicants using a Voight-Kampff machine, a complex interrogation tool, whose process seems to be quite long and tedious. The machine, according to Wikipedia, tracks eye movement (not the glow) of the "subject" during the test, among other things.

I've wondered if this glow was a narrative trick, that the characters are not themselves aware of within the universe of the film. Or if Deckard knows about this too well, but sticks with procedure for his own sake. But I could never find an answer to this question:

What is the reason that Deckard doesn't identify Replicants simply by looking for the "strange glowing quality in their eyes"?

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    I always thought that that 'glow' is merely a reflection of ambient light, not something 'generated' by the eyes.
    – PMar
    Commented Jan 24, 2017 at 14:03
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    In any case, @PMar, it's reproductible in certain adequate conditions, therefore could be part of a test? Commented Jun 2, 2017 at 22:43
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    Maybe the effect is exogetic, i.e., something only the audience can see? Commented Jun 2, 2017 at 23:28
  • I repeat the quote from Director of Photography Jordan Cronenweth: "One of the identifying characteristics of replicants is a strange glowing quality in their eyes". Read it as many times as you need :D Commented Jun 3, 2017 at 17:12
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    @MicroMachine One of the identifying characteristics for the audience, not in-universe. The effect is indeed exogetic, like Chris said.
    – Andres F.
    Commented Oct 10, 2017 at 18:21

5 Answers 5


Deckard can't see it; it's non-diegetic, intended for the film audience, but not for the film's characters. Given that we only ever see the 'glowing eyes' effect when the in-universe characters have not acknowledged it, it tells us that this must be a feature that is not apparent to them.

Additionally, according to Paul Sammon:

Ridley Scott maintains that this effect "was strictly a stylistic device, one more bit of detailing, if you like. If the replicant's eyes really did glow like that within the context of the story, then why would you need a VoightKampff machine to sniff them out?"
-Sammon, Paul M. (2000). "VIII: The Crew". Future Noir: THE MAKING OF Blade Runner.

And of the importance of eyes within the Blade Runner movie is emphasised by Mary Jenkins when she says:

[Ridley] Scott said of the replicants' sometimes glowing eyes: "that kickback you saw from the replicants' retinas was a bit of a design flaw. I was also trying to say that the eye is really the most important organ in the human body. It's like a two-way mirror; the eye doesn't only see a lot, the eye gives away a lot. A glowing human retina seemed one way of stating that".
-Jenkins, Mary. (1997) The Dystopian World of Blade Runner: An Ecofeminist Perspective, Cite note 6

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    It's not about the fourth wall (characters aware that they interacting with the audience), but of non-diegesis (phenomena in text are not experienced by the characters but are experienced by the audience—most movie soundtracks are non-diegetic in that the characters in the film do not hear the music). What you are pointing out is that the flashing pupils are non-diegetic, and the Blade Runner characters cannot see them.
    – Lexible
    Commented Mar 18, 2018 at 5:30
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    @Lexible thanks for the explanation, I didn't know the difference :)
    – Möoz
    Commented May 23, 2018 at 23:31


  • Daryl Hannah - no glowing eyes:

  • Sean Young - no glowing eyes:

  • Rutger Hauer - no glowing eyes:

From your source:

To achieve this effect, we'd use a two-way mirror — 50 percent transmission, 50 percent reflection — placed in front of the lens at a 45-degree angle. Then we'd project a light into the mirror so that it would be reflected into the eyes of the subject along the optical axis of the lens. We'd sometimes use very subtle gels to add color to the eyes. Often, we'd photograph a scene with and without this effect, so Ridley would have the option of when he'd use it

I guess we could reason (in-story) that the replicants have the ability to hide this "glow" at will.

From the filming description above, it also seems likely that creating this "glowing" look would be prohibitively difficult in anything other than relatively stable closeups (although I did choose close-ups for my photos above). I'm guessing that Ridley Scott simply didn't have the time or money to create this look for the entirety of the film (and have explained your question within the plot).

The Voight-Kampff test is, of course, a plot device. The film would be radically different without it.

"Oh, there's someone with glowing eyes, I'll just shoot him..."

Doesn't really seem like it'll be much of a movie, does it...?

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    "Sean Young - no glowing eyes:" - depends on your definition of glowing... Commented Jun 2, 2017 at 19:43
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    The quote from Director of Photography Jordan Cronenweth is: "One of the identifying characteristics of replicants is a strange glowing quality in their eyes". The glow can be seen in the eyes of all the characters you mention at some point under certain given circumstances. Commented Jun 3, 2017 at 17:13

You can't tell a replicant just by the eyes, because some humans have artificial eyes, too.

In the first movie, Deckard goes to a guy selling body parts for information. The guy has lots of eyes in jars and claims to have designed the Nexus eyes. He has a shop in some back alley of LA, selling eyes and body parts. [Blade Runner (1982)]

Think about it: Human replicants are for off-world and are illegal on Earth at the time, so how is this guy finding enough business if he's not selling to humans? Sure, there's the replicant animal pet trade, but he has clearly got some human parts on display, and his expertise was on human bioengineering. If you are a human and you lose a eye in a fight, you pretty clearly go to someone like this guy to get fixed up.

A Blade Runner has to make sure he is "retiring" an actual replicant, not just some human jacked up on bioengineering. (That may or may not be illegal, but it seems a rather tolerant-of-bioengineering society, and it's not a Blade Runner's department anyway. Only replicants fall under Blade Runner juristiction. Humans also get court trials and rights, replicants are property that can be "retired" on sight and on-site.)

Therefore, it is not enough to go by the eyes alone, and the Voigt-Kampff Test is essential evidence and a necessary tool.

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    While that is a plausible explanation, can you prove that the glowing eyes are actually diegetic rather than non-diegetic? Commented Feb 2 at 2:50

Lots of films use visual cues for the audience that isn't part of the universe such as unrealistic lighting, shadows, sounds (especially sounds in space!), etc etc etc. Most are rather subtle--meant more for mood and creating thoughtful environments. It's all part of the dramatism. Naturalism in film is the opposite, where everything must be as realistic as possible (see Dogme 95 for extreme examples of naturalism).

So glowing eyes of replicants is simply a device for the audience to help convey a feeling of un-humanness in those characters. To take it further is expecting too much of your films.


Humans have glowing eyes at times, for example taking a picture with flash and a red-eye effect appears.

If we had a more detailed description of that glow in the eyes of the replicants perhaps we could have a better answer.

  • Surely no human eye glows when viewed directly by human eyes? That is what's being asked here. Commented Jun 2, 2017 at 18:59
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    @Gallifreyan: this is because of light positioning. Spotlight operators often do see red-eye under "normal" viewing conditions from large distances. The blade-runner effect is leveraging this. I point this out because this is indeed a good reason not to execute humans based on such a test.
    – Yorik
    Commented Jun 2, 2017 at 21:27

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