True or false? Your green laser pointer is more powerful than your red one. The answer is almost certainly false. They are, most likely, the same power, but your eye is far more sensitive to green, so it seems stronger. [Brandon Li] was thinking about how to best represent colors on computer screens and fell down the rabbit hole of what colors look like when arranged in a spectrum. Spoiler alert: almost all the images you see of the spectrum are incorrect in some way. The problem isn’t in our understanding of the physics, but more in the understanding of how humans perceive color.
Perception may start with physics, but it also extends to the biology of your eye and the psychology of your brain. What follows is a lot of math that finally winds up with the CIE 1931 color space diagram and the CIE 2012 system.
Some people obsess about fonts, and some about colors. If you are in the latter camp, this is probably old hat for you. However, if you want a glimpse into just how complicated it is to accurately represent colors, this is a fascinating read. You can learn about the Bezold-Brücke shift, the Helmholtz-Kohlrausch effect, and the Abney effect. Maybe that’ll help you win a bar bet one day.
The post winds up in the strangest place: spectroscopy. So if you want to see how color representation applies to analyzing blue sky, neon tubes, and a MacBook display, you’ll want to skip to the end.
We’ve nerded out on color spaces before. In some cases, the right representation is everything.
In fairness the light I can see coming off my green Laser maybe the same power as my dimmer redness.
But most likely if I could see IR I would see nearly as powerful IR laser!
It’s quite shocking how poorly filtered typical flea market green lasers are.
Yes, I have a “legal” green laser pointer purchased from a legitimate retailer stateside. I measured it to produce its advertised output power of 5 mW, and it’s all in the green — no measurable IR at either 850-ish or 1064 nm.
I have another, purchased from a vendor in a mall in Beijing. Also labeled “5 mW” it actually puts out more than 100 mW of power, with only 50 mW of that in the green: The remainder is IR. This thing is truly hazardous, but at least it is highly visible.
Interestingly, the higher power one is also more efficient: Drawing 1.5 watts to make the 50 mW, vs. the 300 mW the smaller one drinks to make 5 mW.