Author Topic: Perception  (Read 20596 times)

Offline Glom

  • Saturn
  • ****
  • Posts: 1102
Perception
« on: November 17, 2012, 08:43:59 PM »
I'm sure this is relevant somehow. But I'm staring at these leaflets watching them change colour in the lighting of this establishment. One second the the "coming soon" circle is blue, the next its yellow. The strangest part is that the lights alternate between red and blue so where does the yellow come from?

It shows how weird perceptions can happen. Too often HB's fail to recognize the lack of common sense in what we see sometimes. The rigidity of their interpretations is their undoing.

(yes I'm also quite bored. 1hr 20m till chucking out time)

Offline smartcooky

  • Uranus
  • ****
  • Posts: 1959
Re: Perception
« Reply #1 on: November 18, 2012, 03:03:38 AM »
The "coming soon" disk is "magenta" in colour



In photography, colours are "additive" (RGB) and "subtractive" (CMY) but a lot can also depend on the "anomalous reflectance" of the ink or dye. Certain inks, dyes and bleaches can reflect more strongly in colours other than that which the eye sees. "Anomalous reflectance"  is caused by high reflectance at the near infrared end of the visible spectrum, where the eye has little sensitivity. Its why photographing red flowers can be tricky. Also, ever noticed that in some photos, a bride's wedding dress can appear to have a blue colour cast? This is because some of the bleaches used to whiten the dress emit UV light, and while the human eye cannot see it, film and digital camera CCD can see but can only show it as a faint blue.

In your case, I am guessing that some sort of "subtraction" is going on, so when the lights go red, the red is being subtracted from the magenta being reflected by the impure spectra of the red light, giving yellow.

Just to give you an idea about impure colour spectra, lets imagine that we have two colour filters, a "perfect" blue filter and a "perfect"red filter (there is in fact no such thing as a perfect filter, but lets just assume for argument's sake, that they are perfect). Now we place the two filters, one on top of the other, and then hold them up to a white light. What colour would you expect to see?
If you're not a scientist but you think you've destroyed the foundation of a vast scientific edifice with 10 minutes of Googling, you might want to consider the possibility that you're wrong.

Offline cjameshuff

  • Mars
  • ***
  • Posts: 372
Re: Perception
« Reply #2 on: November 18, 2012, 02:04:48 PM »
A lot of dyes, pigments, and light sources can have a rather limited number of discrete bands, causing unexpected results under colored illumination. It needn't even be very strongly colored...consider how different colors appear under sodium street lights. The spectrum looks like this:


Objects under sodium light often don't just look their normal color with a pinkish-orange cast. If a pigment reflects most of its light in the dark bands, it'll just look black under sodium light. Or it may reflect in an assortment of narrow bands, some of which fall in the dark areas of the spectrum, giving it a completely different appearance.

Offline nomuse

  • Jupiter
  • ***
  • Posts: 859
Re: Perception
« Reply #3 on: November 19, 2012, 05:06:29 AM »
The proliferation of LED flashlights is going to lead to all sorts of confused color perception.  The more recent multi-color "white light" LEDs, like the tetrachromatics, render color better but the efficiency and price point of the blue-LED-with-YAG-"amber"-phosphor means they'll probably dominate the penlight and cell phone light market for years to come.

As a one-time theater designer, and an amateur graphic artist, I've already been in those horrible conversations with a client about what color something "really" is.  I can only imagine how many more of those conversations are going to occur, as people take a cell-phone pic of their drapes, illuminated by warm-light CFLs, and then start an argument at the local Orchard Supply over the paint chip they are waving around under the high-pressure sodiums (or whatever high efficiency overhead lighting they are using now).

At least these days I only have to argue perceptual volume levels (usually trying to convince people the drummer hasn't gotten any less noisy, it is just that you've become habituated to it.  Which usually happens right about the time hearing fatigue sets in and the high end begins to shut down and the same client begins complaining about the sound not being as bright and crisp as it was an hour ago.....)

Offline ka9q

  • Neptune
  • ****
  • Posts: 3014
Re: Perception
« Reply #4 on: November 19, 2012, 08:08:44 AM »
lets imagine that we have two colour filters, a "perfect" blue filter and a "perfect"red filter (there is in fact no such thing as a perfect filter, but lets just assume for argument's sake, that they are perfect). Now we place the two filters, one on top of the other, and then hold them up to a white light. What colour would you expect to see?
Black. (If you consider that a color.)

« Last Edit: November 19, 2012, 08:15:32 AM by ka9q »

Offline ka9q

  • Neptune
  • ****
  • Posts: 3014
Re: Perception
« Reply #5 on: November 19, 2012, 08:14:11 AM »
I can only imagine how many more of those conversations are going to occur, as people take a cell-phone pic of their drapes, illuminated by warm-light CFLs, and then start an argument at the local Orchard Supply over the paint chip they are waving around under the high-pressure sodiums (or whatever high efficiency overhead lighting they are using now).
That's why any decent paint store will let you borrow their book of paint chips (or at least the chips of the colors you're considering) so you can take them home and see how they'll look under your own lighting and against your other furnishings.

The only remaining problem is that small samples don't look the same as an entire wall covered with the same color. The wall will look darker and/or more intensely colored than the chip. I learned that when I let my wife pick the new color for our internal walls. I don't like darkly colored walls (it's entirely pragmatic - it makes the room harder and more expensive to light) so I always opt for the lightest color she'll tolerate and then it'll be just barely bright enough for me.


Offline ka9q

  • Neptune
  • ****
  • Posts: 3014
Re: Perception
« Reply #6 on: November 19, 2012, 08:17:18 AM »
Which usually happens right about the time hearing fatigue sets in and the high end begins to shut down and the same client begins complaining about the sound not being as bright and crisp as it was an hour ago.....)
Having listened to my share of loud music in my youth, I now wish my high end would shut down -- at least when there's no external sound in that range.

Offline JayUtah

  • Neptune
  • ****
  • Posts: 3787
    • Clavius
Re: Perception
« Reply #7 on: November 19, 2012, 11:57:18 AM »
Having listened to my share of loud music in my youth...

Ditto, plus in my case a long string of increasingly powerful engines.

Quote
-- at least when there's no external sound in that range.

What?  ;D
"Facts are stubborn things." --John Adams

Offline Zakalwe

  • Uranus
  • ****
  • Posts: 1588
Re: Perception
« Reply #8 on: November 19, 2012, 12:29:08 PM »
Having listened to my share of loud music in my youth, I now wish my high end would shut down -- at least when there's no external sound in that range.

Ditto for me. Add in riding motorbikes.....
"The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.' " - Isaac Asimov

Offline smartcooky

  • Uranus
  • ****
  • Posts: 1959
Re: Perception
« Reply #9 on: November 19, 2012, 04:11:37 PM »
lets imagine that we have two colour filters, a "perfect" blue filter and a "perfect"red filter (there is in fact no such thing as a perfect filter, but lets just assume for argument's sake, that they are perfect). Now we place the two filters, one on top of the other, and then hold them up to a white light. What colour would you expect to see?
Black. (If you consider that a color.)



Yep. You should see nothing at all. No light whatsoever would get though the filters.
If you're not a scientist but you think you've destroyed the foundation of a vast scientific edifice with 10 minutes of Googling, you might want to consider the possibility that you're wrong.

Offline Donnie B.

  • Earth
  • ***
  • Posts: 143
Re: Perception
« Reply #10 on: November 19, 2012, 04:18:22 PM »
Tinnitus much?

I once had an episode of low-frequency tinnitus.  I could only hear it when my ear was covered (like, lying on my side with my head on a pillow).  It was a sort of thwupping sound, repeated about once a second... but with occasional pauses or delays.  It was pretty maddening, but I could avoid it by lying on my back or other side.

My best guess is that I was having some sort of muscle spasm in the (inner?) ear, sort of "aural hiccups".  It lasted about two days, then went away.  It hasn't happened since.

ETA: in reply to ka9q, if it wasn't obvious.

Offline ka9q

  • Neptune
  • ****
  • Posts: 3014
Re: Perception
« Reply #11 on: November 19, 2012, 06:40:56 PM »
I once had an episode of low-frequency tinnitus.  I could only hear it when my ear was covered (like, lying on my side with my head on a pillow).  It was a sort of thwupping sound, repeated about once a second... but with occasional pauses or delays.  It was pretty maddening, but I could avoid it by lying on my back or other side.
Sure you weren't hearing your own pulse? Given the ear's sensitivity, it's kinda surprising we don't hear the blood pulsing through the nearby capillaries more often, especially when your blood pressure is high.
Quote
My best guess is that I was having some sort of muscle spasm in the (inner?) ear, sort of "aural hiccups".  It lasted about two days, then went away.  It hasn't happened since.
The spasm could be in the stapedius or tensor tympani muscles. They're both in the middle ear where they form an AGC (automatic gain control) mechanism. The stapedius is attached to the stapes, one of the bones in the middle ear, while the tensor tympani is connected to the base of the malleus. The acoustic reflex causes them to contract involuntarily in response to loud sounds, dampening the motion of the bones and reducing the ear's gain.

The tensor tympani is controlled by the trigeminal nerve. I have periodic problems (trigeminal neuralgia) with that nerve, and in an episode several years ago that muscle contracted randomly without sound input. Very annoying.

Evolutionary trivia note: the three bones of the middle ear are a distinguishing feature of all mammals, evolving from what were originally bones in the jaw. Cetaceans (whales and dolphins) still listen primarily through their lower jaw bones.

« Last Edit: November 19, 2012, 07:26:11 PM by ka9q »

Offline Echnaton

  • Saturn
  • ****
  • Posts: 1490
Re: Perception
« Reply #12 on: November 19, 2012, 07:29:18 PM »
Sure you weren't hearing your own pulse?

That happens to me off and on.  Usually when hiking up a long hill traverse at a fast pace.  Occasionally when I have mixed coffee and pseudoephedrine.  In either case it means I need to slow down what I am doing.

My hearing impairment, as a result of a misspent youth, means that some sopranos sound distorted.  It is like they are overamplified through to small of a speaker.
The sun shone, having no alternative, on the nothing new. —Samuel Beckett

Offline Donnie B.

  • Earth
  • ***
  • Posts: 143
Re: Perception
« Reply #13 on: November 19, 2012, 09:30:27 PM »
I once had an episode of low-frequency tinnitus.  I could only hear it when my ear was covered (like, lying on my side with my head on a pillow).  It was a sort of thwupping sound, repeated about once a second... but with occasional pauses or delays.  It was pretty maddening, but I could avoid it by lying on my back or other side.
Sure you weren't hearing your own pulse? Given the ear's sensitivity, it's kinda surprising we don't hear the blood pulsing through the nearby capillaries more often, especially when your blood pressure is high.
Quite sure.  It was neither correlated with my heart rate nor did it sound at all like the rushing of blood, which I have heard on a number of occasions.  This was a very different sound, one I'd never experienced before or since.

Although it cleared up on its own it did give me some real sympathy for people who have long-term problems with tinnitus.  I can see where it would drive you bonkers.

Offline Kiwi

  • Mars
  • ***
  • Posts: 471
Re: Perception
« Reply #14 on: November 21, 2012, 05:53:08 AM »
...Too often HB's fail to recognize the lack of common sense in what we see sometimes. The rigidity of their interpretations is their undoing.

True.  When I got seriously into photography in the early '70s I slowly became astonished over how lousy my perceptions had been of what I saw -- how many things I had "seen" but never really noticed and appreciated for what they really were.

I had always considered above-ground power and telephone lines to be ugly eyesores, but then I found that with the right lines and the right light of a low sun glinting off them, and with the right scenery and background, and the right exposure on the right slide film (prints from negatives are often useless), they could actually make surprisingly attractive photos.

Also, I had never noticed backlighting and rimlighting before.  Later in the 70s and 80s, in winter I often went out for a lunchbreak to a nearby intersection where the low noon sun shone along one of the streets and beautifully rimlit the long hair and winter clothing of pedestrians as they crossed at the traffic lights.  It was fantastic to relax and watch and appreciate over and over the sights which I had never noticed before getting into photography.

Sometimes I wonder if the "no stars" thing crops up because of movies and TV, particularly space stories.  Of course there are always stars showing in bright sunlight (which is impossible in real life), but how often do they give us a vista of real, recognisable constellations?  We can't expect to see those in the Star Wars movies because they are filmed "in a galaxy far, far away", but surely we should be able to see them in something that's set in our own solar system.

There's an ad on New Zealand TV at the moment which shows twinkling "stars" that look nothing like the real night sky, and in over 50 years of viewing them, I can only ever recall seeing one case of any fictional advertisement, TV programme or movie showing recognisable constellations.  I was amazed!

Instead we often see the sort of nonsense like in (IIRC) the Leonardo DiCaprio movie The Beach.  A girl in the tropics had a Hasselblad with a standard lens on a tripod, pointed the camera almost vertically up, and took time exposures of a few seconds.  "So far, so good for once," I thought. "If we see the results there should be slightly streaked stars near the ecliptic."  We did see the results, but they were very long exposures with stars circling the north celestial pole and taken from about 40 to 50 or even 60 degrees north latitude.  To get just a slightly similar shot, with the pole star close to the horizon, the lens axis would have needed to be nearly horizontal.

Another thing that wakes us up regarding our perceptions is to see an extremely wide-angle photo of a recognisable scene, such as a shot of a long brick wall with the lens axis at right-angles to its centre.  Often viewers will exclaim that the wall is distorted, but, except for the usual minor distortions of most lenses, that might not be the case.  The main problem is that our brains are too good at reinterpreting things we see and making them acceptable to us.  We need to study that wall from the same perspective as the camera, turning our head up, down and to both sides, and noting how the lines of of the bricks recede to a vanishing-point in all areas except those very close to the lens axis.

It can be quite startling to stand at the centre of an end wall in any large, rectangular room in a house and hold up two straightedges so that they match the joins between the side walls and ceiling or floor.  Betcha your brain has been deceiving you all along over how sharply they converge to a vanishing-point.
 
Perceptions, experiences, emotions, memories and understanding are everything, and very important during circumstances which don't match any previous experiences we've understood.

I guess those are what make most of us poor eyewitnesses of any out-of-the ordinary or frightening event.
« Last Edit: November 21, 2012, 06:56:32 AM by Kiwi »
Don't criticize what you can't understand. — Bob Dylan, “The Times They Are A-Changin'” (1963)
Some people think they are thinking when they are really rearranging their prejudices and superstitions. — Edward R. Murrow (1908–65)