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#1
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Depth perception and contrasting colours
I have long enjoyed stereo photography, in cross-eyed and parallel
free-view, anaglyph through coloured glasses and cross-polarised projections. I was interested to see the "stereo" effect (unintentional) which can be seen on some webpages which use strongly contrasting colours. Like so: 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? Does it work with one eye closed? (It doesn't for me.) More interestingly, can anyone offer a simple, understandable explanation for the effect? 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?) -- Jeff R. (more than one dimension) |
#2
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Depth perception and contrasting colours
"Jeff R." wrote in message
... I have long enjoyed stereo photography, in cross-eyed and parallel free-view, anaglyph through coloured glasses and cross-polarised projections. I was interested to see the "stereo" effect (unintentional) which can be seen on some webpages which use strongly contrasting colours. Like so: 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 genuinly 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. That said the website you've given isn't a particularly good one to show it up, it's more obvious when the contrasting colours are large and touching or one on top of the other, try pink(magenta) on blue. 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. 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. 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. 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) 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. So if you're in the habit of taking photos of fully saturated pink mountains against saturated blue skies look out! Cheers, Calvin |
#3
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Depth perception and contrasting colours
On 2009-08-28 00:07:42 -0700, "Jeff R." said:
I have long enjoyed stereo photography, in cross-eyed and parallel free-view, anaglyph through coloured glasses and cross-polarised projections. I was interested to see the "stereo" effect (unintentional) which can be seen on some webpages which use strongly contrasting colours. Like so: 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? Does it work with one eye closed? (It doesn't for me.) More interestingly, can anyone offer a simple, understandable explanation for the effect? 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?) Color contrast is one of many testing and correction methods used in optometry. A part of the Humphriss Immediate Contrast Test, is to have two solid black square targets, one on a green field and one on a red field. The eyes are tested individually and then binocularly Due to focus in front of the retina for the shorter wave length, higher frequency green and behind for the longer WL, lower frequency red, one target will appear sharper than the other until correcting lenses balance the vision binocularly. Then the targets should be seen with similar clarity. This is one of the reasons the old 3D glasses were one green and one red lens, they screwed with your binocular balance to create the illusion of 3D. -- Regards, Savageduck |
#4
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Depth perception and contrasting colours
Jeff R. wrote:
I have long enjoyed stereo photography, in cross-eyed and parallel free-view, anaglyph through coloured glasses and cross-polarised projections. I was interested to see the "stereo" effect (unintentional) which can be seen on some webpages which use strongly contrasting colours. Like so: 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? Yeah I see it. Does it work with one eye closed? (It doesn't for me.) Likewise, it disappears for me with one eye closed too. More interestingly, can anyone offer a simple, understandable explanation for the effect? Others have suggested the different focal length for different coloured light, but I don't think it would make that much effect, plus if that was the cause it should still be present with one eye closed. Also if that was the cause, the stereo effect should increase as you get closer (as the difference in focus increases), and disappear with distance. Whereas I find the opposite, as I get closer the 3D effect lessens, as I get further away it increases until I'm about 3ft from the monitor. I put it down to an effect caused by the Bayer filter on the retina, and a slight bug in the Brain's raw image convertor and 3D engine. ;-) 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?) I've observed similar effects with highly saturated slides too - eg photos of flowers, green meadows & blue sky. Curiously the effect seems to disappear when projected. When I first saw the effect with slides, I thought the effect was caused by the different colour layers, but then I noticed the perception didn't reverse when the slide was turned over. And thinking about it more it couldn't be, because on a slide the primary colours are made by subtraction from multiple layers. -- Jeff R. (more than one dimension) |
#5
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Depth perception and contrasting colours
Calvin Sambrook wrote:
"Jeff R." wrote in message Like so: 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. 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. 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) 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 http://astro1.panet.utoledo.edu/~lsa.../19_wheatS.jpg 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...r/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. |
#6
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Depth perception and contrasting colours
Savageduck wrote:
Color contrast is one of many testing and correction methods used in optometry. A part of the Humphriss Immediate Contrast Test, is to have two solid black square targets, one on a green field and one on a red field. The eyes are tested individually and then binocularly Due to focus in front of the retina for the shorter wave length, higher frequency green and behind for the longer WL, lower frequency red, one target will appear sharper than the other until correcting lenses balance the vision binocularly. Then the targets should be seen with similar clarity. This is one of the reasons the old 3D glasses were one green and one red lens, they screwed with your binocular balance to create the illusion of 3D. Well, I use blue and red, but not to quibble. The purpose of the coloured glasses in anaglyph 3D is (surely) only to present different images to each eye - to separate the left image and make it visible to the left eye, and vice versa. Whilst I freely acknowledge the differential focussing you explained, I don't think that has any effect on anaglyphs, which are essentially monochrome. I've been wrong before, though. -- Jeff R. |
#7
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Depth perception and contrasting colours
Doug Jewell wrote:
Others have suggested the different focal length for different coloured light, but I don't think it would make that much effect, plus if that was the cause it should still be present with one eye closed. Also if that was the cause, the stereo effect should increase as you get closer (as the difference in focus increases), and disappear with distance. Whereas I find the opposite, as I get closer the 3D effect lessens, as I get further away it increases until I'm about 3ft from the monitor. I put it down to an effect caused by the Bayer filter on the retina, and a slight bug in the Brain's raw image convertor and 3D engine. ;-) Don't forget our over-active built-in anti-aliasing filters... The getting closer/further away effect is what got me started on all this. I've just got a new set-top box on my telly, and it has a blue on/off LED. When I'm sitting on the lounge, watching the box, (a large proportion of my life) the LED appears to be buried deep within the bowels of the box. When I look at it close-up, it appears to be flush with the front panel. More trickery. Of course, the conspiracy theorist in me says that the LED is mounted on tracks, and it detects my position and retracts accordingly. -- Jeff R. (adjusting the tinfoil hat) |
#8
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Depth perception and contrasting colours
Jeff R. wrote:
Calvin Sambrook wrote: it's more obvious when the contrasting colours are large and touching or one on top of the other, try pink(magenta) on blue. This what you meant? http://www.mendosus.com/photography/colour-stereo.html (updated with new image) http://www.mendosus.com/photography/six-colour.gif -- Jeff R. |
#9
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Depth perception and contrasting colours
"Jeff R." wrote in message ... I have long enjoyed stereo photography, in cross-eyed and parallel free-view, anaglyph through coloured glasses and cross-polarised projections. I was interested to see the "stereo" effect (unintentional) which can be seen on some webpages which use strongly contrasting colours. Like so: 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? Does it work with one eye closed? (It doesn't for me.) More interestingly, can anyone offer a simple, understandable explanation for the effect? 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?) -- Jeff R. (more than one dimension) Interesting. It reminds me of a color display I saw back in the 1970's. It worked by putting the three colors at different levels on the screen, and accelerating the electron stream at three different energies, in order to get it to penetrate the glass to the different levels necessary to get the three different colors......Rather complex and expensive, but it worked...... |
#10
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Depth perception and contrasting colours
"Jeff R." | Can everyone here see the apparent differences in depth of the coloured text | on that page? yes | Does it work with one eye closed? yes | More interestingly, can anyone offer a simple, understandable explanation | for the effect? differing points at which the various wavelengths focus (as put well by others) |
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