shades of grey - part II

[Derek]

Not shades of grey, really. But here's another one:

Have a look at the picture below. What colors do you see? Red, green, yellow, brown maybe? In fact, what you are looking at is a monochrome red image, with a black and white overlay. The only 'real ' color here is red, since the picture was printed using only red ink. However our brain tends to 'see' other colors being present. The illusion works best under slightly yellow light, in other words direct sunlight is not the best way to view this illusion.

[Corey]

Very cool.

[eric_darling]

Computers don't translate color in the same way that printers do. If you were to really analyze the image, you'll see there's a healthy mix of each of the RG and B values (although they lean toward R, it's not just strictly R values). Take it into Photoshop, use the eyedropper tool, and you'll see. Alternatively, browse the image inside a Firefox browser window that has the ColorZilla extension installed, and you can eyedrop it directly.

[HMMurdock]

Yeah... the computer isn't really the way to do this. I've seen it done in person with a black and white picture of some LifeSavors that was taken through a red filter. When it was displayed again through a red filter and it appeared to have color again (though it leaned heavily on the red end of the spectrum, no blues or violets)

I have no doubt that the phenominon described in the explination on http://www.grand-illusion.com does exist, however I don't believe it is the explination for these types of displays... My understanding is, the constructive/destructive interference between the white light and the red light cause the other colors to be more pronounced (since white light has all colors present) so you really are seeing yellow and green, it's not really an "illusion" per se. (of course that is a greatly simplified explination) I believe this also explains the starnge effects of a "black" light.

But then again, I my be way out of my league here, and Mr. Wizard may soon correct me.

[HMMurdock]

Woops... wrong link above... should be: http://www.grand-illusions.com/

[Corey]

Well I know for sure that sometimes when you "add white" to certain colors, i.e. "reduce their opacity against a white background" you see the weight of the component colors change. For example some blues, which are "very blue" will show slightly purple/mauve as you reduce their opacity against white, implying red. (Fig. 1) Also if you take an orange which is 50% red and 50% yellow and then reduce it's opacity against white it will show yellow and there will "appear to be" no red after a certain point. (Fig. 2) That's just stuff I've observed, I'm certainly no expert in additive/subtractive color theory.

You could study color theory your entire life and still not be 100% sure of everything, that's the beauty of art, i.e. the role that nature plays in it whether we like it or not.

[HMMurdock]

Funny you should use that example, Corey. I was having that problem with our logo, and creating a custom theme for Setup Factory. Our logo is yellow lettering with a blue "swoosh" and I took the blue and made a gradient from the blue to white and used it for the background. Everyone complained and said it looked too purple.

[Corey]

Sure, I've run into stuff like that a million times, especially when using CMYK (print) colors. If you are using Photoshop it's easy to fix. A lot of times the easiest way is just to create a hue/saturation adjustment layer (non-destructive edit) above the "blue" layer, group it (CTRL + G), so that it's masked "just to the blue area" and then just double click on the adjustment layer and drag the hue slider a bit until it's the right kind of blue, you'll see the change in real time so you can go by eye. You can do this on semi-opaque layers so it works well in the sense that what you see is what you'll get. It's sometimes tricky to get pure blue with a fade though, it either tends to go cyan/purple on you or sometimes even grey, but using adjustment layers is one way to eliminate some of the difficulty.