Time for some more color talk. On Thursday we saw how reflected color works. But what about color that isn’t reflected but beamed directly at us? Like what’s coming out of the monitor directly in front of you right now?
What you see here is a screen capture of my monitor showing a hugely enlarged picture. You’ll note at the top that it tells us it’s displayed at 1200% – which is the maximum Photoshop will do. Here’s what it looks like actual size:
Note that this is also a screen capture, not a photograph. It’s exactly what Photoshop displays on the monitor.
The color squares weren’t randomly chosen. The bottom row is Green, Red and Blue. Did you know that when a picture is in RGB mode that this is what’s being referred to? R: Red, G: Green and B: Blue. These are fundamental colors of light for projection screen, computer monitors and old-style CRT displays. In all cases, the only colors being produced by the unit are red, green, and blue. Every other color is built up from these.
Okay fine, whatever. Starting to get boring. So let’s inject some interest. Rather than looking at screen shots, let’s break out the old camera and take a picture. Realize that when asked for a closeup, Photoshop presented the view that started this discussion – beautiful, clean squares of color. Is that REALLY what’s there when you try to look closely?
Well, here you go. What I’m showing below is a true close-up picture of the tiny color squares shown above, taken with my trusty DSLR:
So, can you spot the differences between this and what Photoshop showed you? I’ll bet you can 
It sure doesn’t look much like the Photoshop image, does it? What you’re seeing is a closeup of the color elements (let’s call them pixels) that exist on my flat screen display. I showed you the actual screen image (the little squares) so you’d see what your eye sees when looking at the monitor. But this is what’s really there (as much as there’s any "really" in the real world). If we zoom in closer we’ll see this:
Notice that at this scale you can see there there are (almost) only the three colors – red, green, and blue. Certainly in the red, green and blue squares that’s all you see. If you look at the blue rectangle at the top, you can see that the blue pixels continue straight down into the lighter blue rectangle beneath. Similarly, the green pixels of the green rectangle at the bottom left continue up into that light blue square as well. So what we’re seeing is that the nice light blue is actually made up of deep blue and green.
Even more interesting, the yellow square in the center is formed from just two colors – green and red. If you look at the green and red rectangles beneath it you can see that these pixels continue up and form an alternating green/red pattern which results in our seeing yellow. That’s pretty weird – a light color like yellow being formed by displaying two not-light colors like red and green.
You’re probably also noticing that the green pixels look to have turned a bit blue-green when they’re in the light blue square and the red pixels look more orangy. That’s a result of the particular physics underlying my monitor and for clarity you can safely ignore it. The "take it to the bank" fact is that even if they had displayed bright red and bright green, the result would be yellow.
Whew. That’s enough for now. There’s more to say but this has gone on pretty long already. The key point is that other colors (the light blue, the purple and the yellow squares) are formed from red, green and blue pixels and you’ve now seen the closeup evidence to prove it.
- And that’s today’s word from the bird
