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  • OT understanding colors ...

    Im perplexed about colors,
    mainly because the way were supposedly perceiving them does not totally add up,

    I grasp the concept of what we see of an object as yellow is actually every color but yellow and that's why the spectrum of yellow light is reflecting yellow back at us, same with what we think of a blue object is actually everything but blue, or a green one or red,

    but what about brown?

    here's the part that does not make sense to me, if seeing bright yellow or blue or red is actually an admission that the color brown is really in all of them and that's the very reason you cannot see it, then how come when you mix all of these other colors together you end up seeing it?, the color brown that is...

    just drawing back on what happened when I was a kid and got all my different play-dough colors mixed together...
    Last edited by A.K. Boomer; 02-28-2017, 09:58 AM.

  • #2
    I'm far from an expert on color theory, so keep this in mind. However, colors are displayed as a result of two different methods: additive and subtractive. Additive colors are like those from light. If you took a flashlight that was perfectly red, one that was perfectly blue, and one perfectly green, and shone them on the same spot you'd have a white dot. Computer monitors are this kind of device. With subtractive colors, they're like paint. Take red and blue and yellow, and mix them and you'll get black.

    As for brown, yeah that's still a bit of a mystery to me. Of the neutral colors, it was the one that I never knew how to make from the color wheel.

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    • #3
      A real poor explanation:

      It's confusing be cause we have two ways that we mix "colors". We can mix pigments or we can mix lights. Either way, our eyes can only sense Red, Blue and Green LIGHT. The level of each of those lights are mixed by our brains to be interpreted as other colors.

      There is mixing pigments, where white PAINT reflects all colors and Black reflects none. Then we have mixing light, where if you shine a red light and a blue light and a green light you get white light.

      Pigments subtract light from what whatever light is shined on it. If you shine a red light at a blue dot, you only see a black dot because Blue does not reflect red. Shine a white light on that same blue dot and you will see the blue spectrum of the light reflected.

      What you see as YELLOW is actually a mixture of green and red LIGHT. That means that a yellow dot has to absorb all blue light while reflecting red and green in roughly equal proportions. It also means that the light shining on the dot has to have a red and green spectrum in it. Yellow, orange and brown are all sensed as a combination of red and green LIGHT with little or no blue.

      Like I said, a poor explanation.

      Dan
      At the end of the project, there is a profound difference between spare parts and extra parts.

      Location: SF East Bay.

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      • #4
        Think some of it has to do with the difference between RGB and CYM. red/green/blue when mixed produce white, cyan/yellow/magenta when mixed give black. RGB adds each color, with CYM each color cancels the other.


        Edit:
        with RGB, mixing red and blue gives purple
        With cyb, you mix cyan and magenta (?) to cancel out the red in megenta and produce blue
        Last edited by kendall; 02-28-2017, 11:02 AM.

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        • #5
          It's probably more useful to consider it a little differently.

          A yellow object is not "all other colors", actually it is an object that REFLECTS YELLOW LIGHT. Because it does NOT reflect the other colors, it appears "yellow" because that is the only color (frequency) of light that remains. White paint reflects all colors, black paint reflects no colors (ideally). Clear material filters out no colors.

          Paints, etc are a sort of "filter".

          A colored glass is one that transmits only the one color. It filters out the others. Paint reflects only the one color. This is with single, not mixed, colors.

          When you have mixed colors of paint, they have a mixed reflectivity. You have yellow, and blue, for instance. Your eye perceives this as being green.
          1601

          Keep eye on ball.
          Hashim Khan

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          • #6
            With the question of brown, specifically, I've noticed that you will never really see a bright brown. A bright blue, a bright red or a bright green, yes. Even a bright yellow. But brown is always a a dull color since most of the visible light spectrum is not reflected.
            Last edited by danlb; 02-28-2017, 12:37 PM.
            At the end of the project, there is a profound difference between spare parts and extra parts.

            Location: SF East Bay.

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            • #7
              Additive - adding light

              Take three adjustable lights - Red, Green, and Blue. Shine them on a spot. As you bring up the brightness of any two you get an intermediate color

              (Red/Green mix) Red -> Orange -> Yellow -> Lime Green -> Green
              (Red /Blue mix) Red -> Magenta -> Purple -> Indigo -> Blue
              (Blue/Green mix) Blue -> Greenish Blue -> Turquoise -> Bluish Green -> Green

              When you start adding three colors together you get more intermediate colors. If you add all three together in equal amounts you get white. If you add more red and a little green, you get something that is orange... around 590 on the periphery of this graph, or at about X = 0.53 and Y = 4.0.




              Subtractive - removing light

              Paint removes colors from light that hits it. If you have a paint that absorbs blue light, and you shine white light on it, then the reflection will be made up of a mixture of red and green light. The color will depend on just how much red is reflected and how much green is reflected (and if any blue is reflected). It might be a bright yellow if all of the red and green are reflected (X = 0.45, Y = 0.55). It might be a dull yellow if just a little red and green are reflected (still X= 0.45, Y = 0.55, but the brightness is reduced) And if a little more red is reflected than green, it will look orange (as above, X = 0.55, Y 0.4). If the overall reflectivity is reduced, it will go from orange to dull orange to brown... So brown is not only an orangish color, it is perceived because of low reflectivity compared to things around it. Take a scrap of dark orange construction paper and put it on a white background and then on a black background. Your perception of it's color name will shift (even though the spectrum of the reflected light doesn't change).

              The color of randomly mixed paint tends towards brown because in general the mixtures are heavy on the colors that absorb blue light... If you look at the color triangle you will see that Red, Orange, Yellow and Green are actually all on one curved leg of the triangle. Mixing those four paint colors will absorb more color from the left lower corner, pushing the reflection (what is left) into the right upper middle... i.e., yellow/orange/brown. As the mixed pigments get more and more effective at removing light, it should go to black. However, cheap pigments are not very efficient, and so we end up with brown.

              Of course, if the light hitting the paint isn't white light, then that changes things. Shining blue light on paint that absorbs blue light will reflect nothing - and it will look black. So something that looks yellow in white light may look almost black in blue light.
              Last edited by Dan_the_Chemist; 02-28-2017, 12:29 PM.

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              • #8
                Knew they were simple terms for coloring, additive subtractive.
                So dosed up with cold meds couldn't think of em.

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                • #9
                  appreciate the explanations -

                  would be interesting to find an "anti color chart" one that shows what my favorite color actually really looks like, must be gawd awful im thinking...

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                  • #10
                    Here is a web page I put up some years ago when I was doing testing for JASC on Paint Shop Pro. It is about how to balance and calibrate colours on a computer to match a printer so it prints out properly. It also explains colours and how they work.

                    http://ixian.ca/color.htm

                    How we perceive colour is a very necessary part of the work I am now doing. Our eyes and brain are not at all linear and we do not all see colours the same. I even have a difference from my left and right eye that made it more difficult to get a pilot's licence.

                    Our eyes are very fast at detecting changes in luminosity (brightness) but are terrible at seeing changes in colour. With colours everything matters, how fast they change, how much they change and what the change in wavelength happens to be. We are far more sensitive to green light than red or blue. We are tricolour animals but the sensitivity of the cones in the retinal centralis area have a spectral overlap that stretches far into each of the other colours. The amount of overlap varies quite a lot so even if we see approximately the same colours in red, green and blue the overlapping in between areas can be a lot different. Brown is just dim yellow, not really a different hue (colour).

                    What you see also very much depends on your recent exposure to light, especially bright light. The afterimage effect can stay for quite a long time and it usually cause a reversal of the colour sensitivity. That is where I have had to compensate in my project by using changes in luminosity instead of just changes in colour. I am using exponential curves for the colour changes to compensate for afterimage effects. It doesn't help at all that computer monitors are also very non linear.

                    added: Also, it is know known that what we see and even afterimages are not just caused in the eye but also in the brain. One of the most amazing things I have learned is that the entire visual area for each eye is directly mapped into the occipital lobes at the back of the brain. The neural fibres connect in the same way that we actually see in our visual field. I would sure like to know when that mapping occurs. Is it before we first open our eyes the very first time or does it happen after that time and just how quickly does it happen? That would be a really nice research project in neurology. The main difficulty would be just how do you do it? We cannot play with a baby's vision so perhaps some sort of lab animal would work. But that would have to be some sort of primate.
                    Last edited by Evan; 02-28-2017, 02:39 PM.
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      Evan, it appears to be learned, and even relearned. There was a study (that you probably know about) where the person wears glasses with prisms to invert their vision. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC311278/

                      The interesting thing is that the subjects quickly learned to see everything as right side up again. Even more fascinating was a later experiment that indicates that the subjects "reduce their motor errors under inverted vision" ( https://www.ncbi.nlm.nih.gov/pubmed/23700129 )

                      The mind is a marvelous thing.

                      Dan
                      At the end of the project, there is a profound difference between spare parts and extra parts.

                      Location: SF East Bay.

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                      • #12
                        But what does it taste like???

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                        • #13
                          The interesting thing is that the subjects quickly learned to see everything as right side up again.
                          We discussed that here a long time ago. From what I recall in some research I did, it was not at all easy for some to go back to normal vision. In particular the man that first tried it on himself had some very serious problems restoring his normal vision. It is very dependent on time as well as age. From birth to several years the brain is rapidly developing and undergoes a period of "pruning" excess neurons if they are not put into use for something. What this indicates is that right from birth a baby should be constantly kept busy with new things to see as well as new places, events, sights and sounds and that includes very early teaching in how to speak normal talk and early reading. My daughter was able to recite nursery rhymes from memory very well by the time she was 2 years old. She was reading long before she attended school. She now owns her own newspaper and is a national award winning photographer.

                          This sort of thing is now being seen in children that are treated for amblyopia by using an eye patch on the "good" eye to force the wandering eye to line up. Patching one eye for too long can cause serious problems that do not easily correct. "Too long" is not very long at all either.

                          The brain is indeed marvelous and I can testify to that. Mine is recovering far more than I thought possible and it is far faster than I ever thought could happen. It is a matter of pushing myself as hard as I can and not letting up. One thing I notice is what always happened in the past. When I work my brain hard I will start to sweat after an hour or two.

                          I have always liked my living space to be extra warm, most likely because I do not have much body fat. I normally keep it at around 24C (75F). But in the evening when I do my best work I let the heat drop and do not notice until it has fallen by about 3 degrees colder. That is a really big drop in room temperature, about 5.4 F colder. Also, when I work really hard it is like time slows down a lot. The clock speed must be accelerating some how.

                          Anyway, must go. I have a meeting at the University tomorrow and demonstration on Friday.
                          Free software for calculating bolt circles and similar: Click Here

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                          • #14
                            I don't know if this relates to the OP's question but when I had my body shop every now and then I would have to paint something just for the sake of rust protection and or the customer didn't care what color it was as long as it was covered with paint...... so what I used to do was dump all my left over paint from previous jobs in a gallon can and stir it up. The results were, I always ended up with a dark blue gray color no matter what I mixed together.

                            JL..............

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                            • #15
                              Originally posted by J Tiers View Post
                              A yellow object is not "all other colors", actually it is an object that REFLECTS YELLOW LIGHT. Because it does NOT reflect the other colors, it appears "yellow" because that is the only color (frequency) of light that remains. White paint reflects all colors, black paint reflects no colors (ideally). Clear material filters out no colors.
                              That is how always thought of it. JR
                              My old yahoo group. Bridgeport Mill Group

                              https://groups.yahoo.com/neo/groups/...port_mill/info

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