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A yellow pixel is created by filtering out only the blue component. In a yellow pixel, 1/3 of the area is red and 1/3 is green. This means that within a yellow 2 x 2 area on the screen, there are 4 open red filters and 4 open green filters.

What would be the perceived color, if in that same 2 x 2 area, 2 red and 2 green filters are open, instead of 4 for each color?

If 2 pixels are yellow and 2 are black, that would be a total of 4 open filters. The resulting color would look like 50% yellow (128, 128, 0 in RGB-terms). Of course only in an ideal case. In reality the backlight would bleed and the color would be a brighter, maybe 75% yellow.

Now to the test:

I tested this theory by using the 50% unicode shading character U+2592 in the Windows command line and then comparing the resulting color to a painted color in Paint.

I chose black as the background and yellow, rgb(255, 255, 0) as the text color and filled the window with the medium shade character. As expected, the perceived color is almost exactly rgb(185, 170, 0) in Paint, which is about 70% the brightness of yellow and a little less green hue.

Repeating the procedure but spreading the 4 open filters over all 4 pixels (2 red and 2 green pixels) leads to pretty much the same result, which is good.

Now I try to reproduce orange:

I should get orange rgb(255, 128, 0) if I have 2 red and 2 yellow pixels in a 2 x 2 area and again using the 50% shade character. But this time, the resulting color is almost exactly rgb(255, 155, 0) in Paint.

The hue is much more on the green end this time. Why is that?

If I use the light shade character U+2591, which is 33% in the Windows command line font, I get exactly orange rgb(255, 128, 0). (By using 67% red and 33% yellow). Again, why do I need much more red and is there a formula that can approximately calculate how a shaded color would look like on a LCD monitor?

  • There's different ways pixels are laid out. WRGB has white + RGB, then there's pentile.... and there's also how your monitor is calibrated and such – Journeyman Geek Jun 2 '16 at 2:34
  • @JourneymanGeek I doubt that the filters are adjusted depending on the color. A red value of 200 is always the same, whether it's a white, a yellow or a red pixel. The calibration only influences how the value of one channel is interpreted, independend of the other color channels. The differences occur by physical reasons. – uzumaki Jun 2 '16 at 3:36
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In short, every single monitor is slightly different. Even two of the same model from the same factory can have different calibrations and color temperatures right off the assembly line. Calibrating the display can help, but this is only minimally effective unless you have a very high-quality display.

Also, surrounding colors will influence how a particular 2x2 set of pixels looks. If the color is surrounded by white it will appear to be a different color than if surrounded by light gray, dark gray, or blue. This is the basis of many optical illusions, as well. This also goes for larger spaces than just 2x2.

Unless you are using a monitor that is calibrated and designed for the exact thing you are trying to do here, it is unlikely you will get the results you expect out of it. There is a reason radiologists will move the scans around on a screen to make sure any anomalies they see are not an artifact of the monitor they are using, and they use high quality displays.

  • First, I'm not comparing monitors, you didn't properly read or understand what I was writing about. Same with the 2x2 set of pixels. I didn't look at only 2x2 pixels, read again. And about calibration: I can only copy what I already wrote to JourneymanGeek. Do you actually KNOW that one filter is controlled dependent of the others, or are you just claiming something? Because I claim that each color channel is controlled individually. If you have a calibrated red channel and then add a blue channel, that doesn't recalibrate the red channel! – uzumaki Jun 3 '16 at 4:09
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    My comment on how every monitor is different was to say that any observation you make is dependent on your monitor and cannot be reproduced exactly on a different monitor. How calibration works depends on the particular monitor; whether passive or active; WRGB, RGB, Pentile or other; the controller board; and other things. My only further response is that you don't seem to know what you are actually asking, or at least cannot explain it effectively. Take a look at this HowStuffWorks page which may help: electronics.howstuffworks.com/lcd.htm/printable – Joshua Nurczyk Jun 6 '16 at 6:53
  • The problem is not, that I cannot explain what I'm asking, the problem is that you just don't understand my question at all. You just keep repeating yourself. And link wasn't helpful at all as I know all this stuff already. Again, I'm not talking about calibration and that phenomenon that I'm talking about has nothing to do with calibration. It can be observed on any LCD monitor with any calibration. As you don't have the necessary technical knowledge about the subject please don't bother replying. – uzumaki Jun 12 '16 at 2:13

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