Color generated 3D effects on screen,just me?

June 1, 2008 7:01 PM

Why does red text on black background appears 'closer to me' than green text on black background, when the two text elements are next to each-other? Other combinations yield all kinds of different 'distances'.

Just curious, what causes this effect? I wear glasses or contacts and am astigmatic in the left eye.

posted by spacefire to health (7 comments total)

You're certainly not alone, either way, although I'm not sure of the science behind why. Opticians use black markings (usually circles where I have gone) on a red and green lit background to discern between close strengths of lenses when doing eye tests.

They'll sit you there looking at them going "is the red clearer?.....or the green." *flick between lenses* "The reeeeeed.......or the greeen".

/flashback.

Does your optician not use this method? I have the same eye issues as you, for reference, even down to the left eye astigmatism. All the best people have those, you know.
posted by Brockles at 7:13 PM on June 1

... any visual stimulus projects slightly different images into each eye because the eyes are in different places on the head. By the process of stereo vision, the disparity between these images is used by the brain to infer distance. Because each eye is actually aimed slightly askew when we look straight ahead, the lens of the eye acts like a prism. Incoming light is thus broken into the colors of the spectrum, which are projected to slightly different locations on the retina. The psychological effect is similar to what occurs when one object is actually closer than another: Some colors are perceived as "closer" than others. A "warm" color, such as red or orange, will appear to be in front of a cooler one, such as green, violet, or black.

... [however], ... the depth effect may actually reverse with low illumination (when the pupil is large, and so the eye focuses differently) ...

— from Graph Design for Eye and Mind. I can't recommend this book enough. Unlike Tufte, who tends to just make stuff up (and, to his credit, gets it right most of the time), Kosslyn actually bases his recommendations (with clear do vs. don't examples) on experiment and published research.
posted by dmd at 7:21 PM on June 1 [1 favorite]

dmd has it. Pure hues will appear closer or more distant as Kosslyn describes depending on their warmth or coolness.

Another factor that affects the perception of distance is saturation. Purer hues seem closer than desaturated colours or colours that have been greyed down by the addition of a complimentary colour, as shown in this figure.

The light reflecting off objects in the distance is recombining to white light, to a certain extent, and getting further filtered by the air and particles in the air. As a result, things that are farther away appear to have less color, or appear to approach gray in color.

posted by maudlin at 7:33 PM on June 1

Also, don't forget that Your Eyes Suck At Blue.
posted by disillusioned at 8:07 PM on June 1

The fundamental reason for this is chromatic aberration, which means that all lenses are also prisms.
posted by Class Goat at 9:06 PM on June 1

spacefire, I asked the same question last year (complete with an image to test the effect) and it's definitely a result of chromatic aberration. Take off your glasses and the effect goes away.
posted by pmbuko at 12:04 PM on June 2

Take off your glasses and the effect goes away.

You meant to say "remove your corneas and lenses".

(Not recommended.)
posted by dmd at 1:11 PM on June 2