The human eye has a huge dynamic range for the amount of light our eyes can use. We can read in bright sunlight and most of us can read by candlelight. Yet the difference in the amount of light from those two source is almost ludicrous.
Trying to decide what light source to use by looking at specifications, instead of repeatedly buying-and-trying, is also almost ludicrous. There are multiple measurements used. The measurements don’t always measure the same things.
The best description I’ve seen recently is in the article “Lumens, Candela, & Lux” by Richard Nance, in the January 2023 issue of Guns & Ammo magazine.
(No, I still have not looked up how I should be citing my sources.)
For the terms lumens, candela, and lux,
- lumens is how much light comes from a source,
- candela is the intensity of the light in a chosen direction, and
- lux is the amount of light on a surface when it’s a specific distance from the light source.
If I’m buying a light for my desk or nightstand, I’ll probably start looking for a lux specification. For portable lights like flashlights or worklights, I’ll look at both lumens and candela to see how much light there (theoretically) is and how focused that light should be. A small focused beam of light is great when I want to see tiny detail. A wider beam is better if I want a more panoramic view, such as if the power goes out and I want to see the entire room well enough to not run into the nearest table.
Light temperature is an entirely different topic.
And then . . . ugh. The article mentioned there was a flashlight standard, ANSI NEMA FL 1. I thought that would interesting to look at. And it was interesting, in a way that’s mildly frustrating and not at all what I expected. I’ll make that a part 2. There might be a part 3 where I post some good links I found about the flashlight standard which don’t cost at least five hundred dollars to view.
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