Post by Jeff R.http://www.mendosus.com/photography/colour-stereo.html
Can everyone here see the apparent differences in depth of the
coloured text on that page?
Can anyone resolutely *not* see it?
I'd be very surprised if anyone genuinely couldn't see it as I
understand it to be the result of fundamental physics and physiology
rather than an optical trick as much 3d stuff uses.
"Optical trick" is a bit harsh, I think. All the techniques I am aware of
serve simply to present a slightly different image to each eye - each image
offset by (ideally) the spacing of one's eyes.
Contrasting colours on a black background provide a very real stereo
illusion, but I can't for the life of me see how it could be presenting
different (offset) images to each eye.
... That said the
website you've given isn't a particularly good one to show it up,
Really?
Is the illusion obvious to you in the first few (red/blue) line groups?
it's more obvious when the contrasting colours are large and touching
or one on top of the other, try pink(magenta) on blue.
Not sure I follow what you mean by "large", but I'll give it a go. Stay
tuned for updates.
Post by Jeff R.Does it work with one eye closed?
(It doesn't for me.)
It certainly should as the effect is within the eye rather than
between eyes IYSWIM.
Yes, I follow, but my experience is that the effect *almost completely*
disappears when I close one eye. I think I'm kidding myself, but I fancy
there is only a tiny, marginal effect when viewed monocular, but there is
certainly a huge, easy-to-see effect when viewed binocular.
Post by Jeff R.More interestingly, can anyone offer a simple, understandable
explanation for the effect?
From (slightly hazy) memory it's caused by chromatic abberation, or
differential focus, or differential magnification, or differential
colour (pick a term, I've seen all of them used), of the colours by
the simply lens of your eye. Photoraphers see this sort of thing a
lot in lenses, particularly long ones.
Y-e-e-e-es... (trying to figure out how CA would cause a stereo
illusion...)
Do you mean:
The different colours achieve focus at different points (even though the
source is coplanar), so the brain interprets that difference as a difference
in depth?
That makes sense, though it seems contrary to the evidence.
Would I be aware (consciously) of the differential focus? (Would I be able
to sense my eyes trying to focus differently?)
Would/(should?) all the colours appear to be in sharp focus simultaneously?
(as they demonstrably are)
Would this effect work monocularly? (I say it doesn't)
Nice idea.
I'm sure it's (at least) the germ of the answer. (different wavelengths
being interpreted differently)
Your eye/brain is not a simple camera and doesn't just record what it
sees like a camera but rather interprets it to glean information. It's
(incorrectly) interpreting the chromatic abberation and hence
different focal points for the colours as distance information.
(sorry - I repeated what you said)
Post by Jeff R.Googling produces some joy, but not much. (Too tight to pay for
research papers.)
Anyone think there could be implications here for landscape
photography? (Or is the effect too gross/unsubtle?)
Well, it only really happens with fully saturated colours (if you
think about the explanation you;ll see why)
One of the sources I looked at cited a Van Gogh landscape
Loading Image...
in which the pastel-blue sky/clouds appear to stand out behind the
pastel-green fore and mid-ground.
(from http://astro1.panet.utoledo.edu/~lsa/_color/19_depth.htm - good stuff)
I don't know if the effect there is down to colour and depth perception, or
Van Gogh's genius, but either way I do see it... and the colours are pastel,
not saturated.
....which is why it's common
with in additive colour systems (things which emit light like
monitors) and not often seen in subtractive colour systems (paints,
books and printed photos) although there was a superb album cover in
the late 1970's or early 1980's which demonstrated it really well
with a word written in pink on a blue background - I wish I could
remember what it was called.
Likewise I recall a story book from my youth that featured bright red and
blue text on a black background - I found the 3D effect disturbing, even as
a young'un. Had to run my fingers over the book to be sure it was actually
flat. (it was)
So if you're in the habit of taking photos of fully saturated pink
mountains against saturated blue skies look out!
Not too many of those round here, so no risk.
Cheers,
Calvin
Thanks for your input.
--
Jeff R.
