Background

To improve sleep by reducing blue-light melatonin disruption, I wear night-glasses that filter short wavelengths (e.g. something like these). With these glasses on, both the top and bottom bars of this test image will appear visually identical:

RGB wavelength image. Bottom bar with zero blue value (Source: Personally derived from this public domain image and released to public domain)

But the colour spectrum you "see" while filtering the blue light will not appear to be either of these bars; instead some partially de-saturated hybrid of the two. I think this is probably due to a pervasive blue wavelength of the LCD back-light regardless of defined colour contrast.

However, there is something else odd going on. If I wear these glasses for several hours and then remove them for some reason - all the blue colours I should see will be muted, partially de-saturated or even interpreted as a shade of green for at least several minutes afterwards (I haven't stop-watched the effect). Freaky.

Question

Why is this selective shift of colour perception occurring for a while after removing wavelength filtered glasses?

  • I presume that, like sunglasses, when you first put on the glasses you notice a difference. If you leave the glasses on for a while, is that difference still noticeable? If you take them off for a brief moment then put them back on, does it look weird again for a bit? – Amory Oct 30 '13 at 13:31
  • @Amory I'd need a spare day or two to throw my sleep schedule completely out of whack to get a wider range of information. What I already know from prior use is that depending on the underlying spectral mix, blue light sources will appear green, amber or an extremely dim brown while the wearing the glasses. To be expected; but the persistent interpretation of vivid blues as a greenish-cyan or a rather muted washed-out blue for approximately several minutes after removing physical filtration is the unusual thing. I have some ideas what might cause this, but I'd be speculating. – LateralFractal Oct 30 '13 at 22:38
up vote 2 down vote accepted

The short answer is you don't see light you see a reconstruction of your environment made by a learning organ, your brain adapts to changes in stimuli. Color in particular is tricky because there is no objective way for your brain to determine somethings color, it can only see the wavelength that reaches the eye which are affected by everything along the way including the color of your eye's tissues. Your brain adjusts to the filter, until it sees the colors it expects to see again. It does this by becoming less responsive to some signals, in the case of the glasses the colors in between certain ranges. when the glasses are removed the brain is still largely ignoring those signals and has to learn to accept them again in exactly the same way it learned to ignore them.

You can do something similar with glasses that flip the visual field, (turn everything upside down). The work was done by This is a good article. Follow the link for more information. George M. Stratton, and after wearing the glasses eventually you start seeing things right side up again, then when you remove the glasses everything is upside down again, the brain has to again relearn to see right side up.

Wearing colored glasses forces the eyes to work harder to see the normal colors the way they are supposed to be seen. In other words, when you wear, say, green glasses, the sort that overwhelmingly turn everything green, the eyes are trying harder to detect all the colors that are not green, and to desensitize themselves to green.

So when you take the glasses off, your eyes have become used to disregarding green in favor of everything else. Anything green will look a bit washed out, until your eyes adjust. The effect is less pronounced or non-existent with grey or grey-green glasses.

This has been my experience. The exact mechanisms by which it happens? Can't say, don't know.

  • Welcome. Can you add resources to your answer? – AliceD Jun 19 at 11:52
  • John's answer is correct, in that the color adaption mostly happens in the brain and not the eyes. The eyes mainly adjust to light intensity (e.g. 'nightvision') – Nicolai Aug 8 at 15:17

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