[Elecraft] K3, k4 Black knobs

[Rich NE1EE]

On 2020-10-16 13:31:+0000, Ken B wrote:
>Why do you use red  and not blue or green 

Good question.
Long answer that I'll keep short.
In days of old, mariners wanted lights that they could see by, but that are not too visible otherwise.
Enter red lights. Humans eyes are not very responsive to red light. More to blue, and max for green.

But now imagine that you are on a ship, and you want to see stuff, but not be too visible to other ships (military use). So you use red light. It's not discernable as much as white, green, blue...from a distance.

So we continue to use red.

Night vision is pretty sensitive. You'd be surprised at how much you can see at extremely low levels of light. If color rendition is not an issue, then night vision, using the rods, rather than cones, is not a bad idea. But if color rendition is important (think nav charts [I sail and fly at night]), then very dim white light might be more useful. Downside is that the cones, which we use for color, are not nearly as sensitive as rods, which are for shades of grey. So there are trade offs.

I don't see why green or blue could not be used at very low levels. Your eyes are way more sensitive to green, so you could possibly get by with much dimmer green or blue light than red.

There is way more...but this is a good start, and I'll wrap by saying that any of the colored lights will have drawbacks. Depends on what you are looking at. For me, red is a good choice because I can see all my radio gear clearly using a red light, and because it is readily available in the low power that I want. Green and blue (and yellow, etc) are also available, but at higher power. I don't want to overwhelm my rods and then await recovery.