Re: [Non-DoD Source] [RealSTMFC] Was there ever a clinic on Delano-based paint and weathering?


Thank you for the excellent detailed explanation. I learned a lot. Thank you again. Bill S

On Nov 16, 2020, at 11:44 PM, devansprr <devans1@...> wrote:

On Mon, Nov 16, 2020 at 04:44 PM, Bruce Smith wrote:
"Sorry, but you’ve “triggered” me. Please save us from the pseudo-science babble of people like your optometrist friend."

What Bill wrote:
"My optometrist friend rightly points our eyes ‘see’ different colors from  others peoples eyes."
Triggered is a good description of your response - there are two ways to interpret Bill's note. You are correct about the emission and absorption of wavelengths of light coming off a surface, and that the same wavelengths enter all eyes (although cataracts can impact the absorption of specific wavelengths before the light reaches the rods and cones.)

But one could easily interpret the optometrist's remark to include the brain's portion of the process of "identifying" colors, which plays a very significant role in perceiving (and therefore "seeing") colors.

The immediate problem is that color is a perception of intensity over a broad range of wavelengths. This is why without changing the physical makeup of a surface, different lighting sources can make a color appear different  (which is why in the old days you could buy color film for daylight, or for tungsten light sources, or use filters to adjust the distribution of wavelengths entering your camera. Today, digitally, we adjust the "white balance.")

But in my experience you have oversimplified the brain's perception of color, and how people perceive them.

More significantly, people may see different colors depending on the context - what else is in the field of view? This is why I remarked that in most situations, especially those that frequently happen in the real world outside, our eyes are terrible "colorimeters."

My impression of color vision is that the optical portion of your brain never actually "learns" the wavelength of any color in any calibrated sense. Instead we "teach" the brain what a color is based on its previous memories of the color. But for minor nuances in color, the memory of the color also includes the surrounding field of view when "taught" that color. To minimize confusing the brain, minor variances in color are often "taught" with the color surrounded by white. Surrounded by white, the color data received by the brain is not modified by the brain's perception of color, light and shadow, and depth (distance.) But in the real world the brain works really hard to make sense of light, shadow, depth, distance, motion and 3D shapes. From an evolutionary survival standpoint (as both prey and predator), the brain is a lot more concerned with discerning three-D objects, movement, and determining distances and spatial relationships. So color is just one of many continuous vision interpretations performed by our brains that have little to do with the wavelength of light entering the rods and cones.

The problem is that in reality, the brain perceives colors in significant part based on ALL of the colors in the field of view, the lighting, and the perceived presence of shadows.  So while the same wavelengths may be falling into the eyes of two adjacent observers, the odds, in such a "feature rich" environment, of them properly identifying a specific reference color are remote. Note that the brain's effort perceiving the real world is much more sophisticated than observing the colors in a photograph. This was the major portion of the challenge in creating night pilotage systems - the brain is much more "focused" on identifying 3D objects, detecting motion (especially relative motion), and perceiving distance and depth, than it is in determining colors. Artists may focus on color because of the potential for creating illusions of some manner, which also points out that it is the brain that plays a significant role in assessing colors, not just the rods and cones in the back of your eye.

There are many optical illusions on the web to illustrate the variation in the perception of colors. See the following:

For starters, see example two - what if the center color was GN Blue?

And what if example 5 was caboose red? Which one is correct -t eh one alternating with white, or the one alternating with black?

Google "color illusions" and you will find many more. As a colorimeter, the human eye/brain sucks.

I suspect that if you took 4x8 sheets of plywood painted with modest variations of PRR FCC (from a specific era), and distributed them about a wide field of view - perhaps leaned against a railroad museum's varied rolling stock collection, with some in the sun and some in the shade, the odds of even a group of "skilled" observers reliably identifying the FCC panel would be low.

Between different lighting sources, shadows, and adjacent colors distorting the brain's perception of color (and that perception is unique to each brain), I am not interested in precise color matches of freight car colors, and I would agree with the optometrist's statement that "our eyes ‘see’ different colors from  others peoples eyes."  Although I would change "see" to "perceive", and "brains" in place of "eyes", just to reduce confusion.

Dave Evans

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