Where I went to college, Computer Science was (at the time) a part of the College of Science rather than being in Engineering. That was mostly for historical reasons. Originally the computer programming classes had been taught by professors in the Math department, so when they finally decided to create a formal Computer Science department they forked the Math department inside the College of Science.

That meant that we Computer Science majors had to satisfy course requirements for a Science degree instead of an Engineering degree. So where my buddies who were studying EE had to take Statics and Dynamics (basically, Civil Engineering and Mechanical Engineering) I was instead required to take one physical science and one biological science. I took Physics and Zoology.

I was told that these requirements were so that I would have a broad education. We had to take a lot of humanities, too, and I took a lot of Philosophy and Psychology courses in order to fill those credits.

And you know what? A lot of that stuff not only improved me as a human, but it even turned out to be useful professionally. One of the things I ended up doing was to design human interfaces. Psychology and the physiology part of Zoology ended up helping me a lot.

Here's an example of what not to do. There are several things wrong with this pair of color choices.

Physiology tells us that humans are far more sensitive to changes in light intensity than we are to changes in color. When the foreground and background vary a lot in hue and saturation but not very much in lightness, it's much less comfortable. In this case the foreground color has a lightness of 50% and the background color has a lightness of 75%. Here's the lightness plane without any color information:

The contrast ratio is terrible, irrespective of the hues that were chosen. But the choice of red and blue as the specific hues is the worst there is.

Physics teaches us that all lenses are prisms. Feed white light through a concave lens, and the different color components will focus at different distances from the lens. Blue, being the shortest wavelength of visible light, refracts the most and will focus nearest to the lens. Red, being the longest wavelength, refracts the least and focuses furthest from the lens.

Green is in the middle. It's also the color we're most sensitive to. So when you go to the optometrist, it turns out that he selects your correction so that green focuses perfectly, as the best compromise.

But when you're presented with sharp edges (anti-aliased or not) between red and blue zones, it is impossible for you to focus on both of them. The result will always be a bit blurry. And it will be uncomfortable to look at, because your natural focusing system will try to correct constantly, and won't be able to do so.

That's why blue and red, alternating in space or alternating in time, is the most obnoxious and repellent color combination there is. It's what you use if you want to drive people away. (That's why I used that color combination in my "stop deep linking my pictures" animated GIF.)

As I worked on human interfaces I ended up using a lot of things I had studied in fields outside of my specialty. Turns out the University was right: studying broadly is better than narrow concentration.

Posted by: Steven Den Beste in Site Stuff at 05:30 PM | Comments (8) | Add Comment
Post contains 577 words, total size 4 kb.

1 Unless you have red-green deficient color blindness, like I do.  A lot of web sites are a real pain for me.

Posted by: Toren at October 26, 2007 10:16 PM (6CGiQ)

2

That was another thing I learned about. My dad was RG color blind. Since it's an X-linked recessive, and since my mom doesn't carry the gene so far as we know, my brother and I have normal vision and my sister is a carrier.

Turns out that RG color blindness afflicts something like 12 percent of adult males in the US. (As with most X-linked negative genes, the rate for women is much lower.) So that's another thing that has to be taken into account.

When the US military creates maps, they color code. They use red and blue, and by convention red is enemy and blue is friendly. The reason they use those two colors is that even when a man has RG color blindness, he can differentiate them.

But they don't print them on top of one another, so chromatic distortion isn't a factor.

Posted by: Steven Den Beste at October 26, 2007 10:30 PM (+rSRq)

3 They might have changed that after a not-to-amusing incident back in the 80's, that I read about on Baen's Bar.  Ft.Benning, IIRC.  Seems John Ringo and Tom Kratman might both have been in the area for this one, anyway it was one of them that told the tale, and the other chimed in with some details.

The story goes that a platoon was given orders for a night march across the base.  The newbie Lt. leading them got about a mile along,  reached a crossroads,  halted and called his senior NCO's into a huddle.  Pulling out the map, he carefully shined his night light on it (under cover so as not to give away their position--good technique) and noted that their march route had them going along three sides of a square, and it would be much better training to cut straight across the wilds in between them and their destination.  At least one senior Sgt noted the swampy terrain and tried to talk him out of it, but, "Good training!" was the response and "Follow your squad leaders!" was the order of the night.

At this point, I should note several things:
The temperature was about 40 F.
Their unit had just been posted to the base for advanced training, and none of them were familiar with it.
To avoid being seen at a distance, Army night lights are red.
So are most warnings printed on Army maps -- such as the one marked on the swampy area that said, in effect, "This area used for target practice by artillery -- unexploded ordinance everywhere!"

The topper to it all?  An artillery battery was using it for target practice that same night. Fortunately, it was only a "dry fire" exercise, with no actual ordnance expended, so the net result was only a few cases of hypothermia and one very severely dressed-down Lieutenant.

I'm told he was serving in Afghanistan as a Colonel. last year, so I guess he didn't manage any more such fubars... .

Posted by: ubu at October 27, 2007 02:54 PM (LrQ7M)

4 No, the red/blue convention goes back much further than that. I have a pair of books in folio size, the West Point Atlas of American Wars, printed in 1959 where every right-side page is a map. Red and blue ink are used to print the positions of hostile and friendly units in it -- and they didn't invent that convention for that book.

Posted by: Steven Den Beste at October 27, 2007 03:13 PM (+rSRq)

5

The common habit of using red type for links on web pages is a real problem for me.  I often have to highlight an entire page to spot the damn things.  When my friends are redesigning their sites, the very first thing I ask for are blue links.

My maternal grandfather was a true monochromat.  I fail all Ishihara tests except two.  I'm supposed to have anomalous trichromacy (protanomaly) with a tendency to dichromatic protanopia.  As you might imagine, my wife does not allow me to dress myself.    What's interesting is how much I still enjoy color animation (although it's likely my early switch in interest to manga was prompted by it being much more relaxing to look at).  Some colors are weak to me that are strong to others.  For example, red is a dullish brown to me, most of the time.  But I suppose it catches people's attention the way an electric blue grabs mine.  A further oddity is that, on rare occasions, a color will not resove itself to my eye.  Meaning, it has a "non-color." Sometimes it will flicker back and forth between options rapidly (nauseating).  However, in many cases, if I can get someone to tell me what the color is supposed to me, it "snaps" into resolution.

It can be annoying, but I've gotten used to it.  But then again, sometimes I wish I could see the world as most others see it.

Posted by: Toren at October 27, 2007 04:24 PM (6CGiQ)

6

To avoid being seen at a distance, Army night lights are red.

Umm, no. They were red to minimize the effect on your night vision.

Around 20 years ago, they switched the red lens to blue. That screws with your night vision a little more but it isn't as visible to passive light amplifiers ("starlight scopes").

It used to be fun to watch a tank at night with a starlight scope when they hadn't turned off the call light on the radio and got a call. The flash out all the optics and windows in the cupola (M60) looked like a grenade went off in the turret.

Even so, it's really hard to hide from thermal sights.

Posted by: Mark A. Flacy at October 27, 2007 07:28 PM (Ef+b7)

7 Mark: doh. you're right.  I confused two things, one of which I don't recall the details clearly on.  Whichever one of them was telling that part of the story (Kratman, I think?) described something they were doing to avoid letting the light shine out.  Don't remember if it was the huddle or covering up with the sleeping bags from their gear. 

Posted by: ubu at October 27, 2007 10:55 PM (LrQ7M)

8 Well, the blue light tended to wash out the water features on the map (such as swamps, streams, and rivers) until they printed new ones that used a slightly different shade of blue.

Posted by: Mark A. Flacy at October 28, 2007 01:53 AM (Ef+b7)

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