Red light really preserve night vision?

I was recently playing around with my anglehead on a red filter. The red filter makes the output MUCH dimmer than green/yellow/blue filters.

I was wondering if the reason red 'preserves' night vision is because it is usually so dim that it doesn't cause the eyes to adjust too much? Or is it really the color?

I tried staring at some boxes under my table in a dark room with night adapted eyes. I could make out the shapes and some labels on them. After I turned on my anglehead-red for awhile, my night vision was gone for many seconds before I could see the boxes again.

A super-dim white light source seems to have the same effect, which leaves me to wonder how much the color really affects. Negligibly?

For e.g, a screaming 190 lumen Red-orange light source will definitely kill your night vision, no matter the color.

So is it because its Red or is it because red is perceived as dim? And will an equivalently dim white source have the same preservation effect actually?

Yeah, bright light of any colour will kill your night vision. I think,however, dim red light kills it the least of all. Something to do with rods and cones and chemical reactions, I think.

Read quickbeams article on it at flashlightreviews for chapter and verse and try dim lights out in practise. I find that my gerber infinity ultra (new) in red is ok for distant-ish stuff without too much damage and the gerber recon (1AA) on red is very good at any distance - but it is very dim indeed.

My Dad worked in photographic darkrooms all his life and he used to wear deep red goggles for about fifteen mins before going in to develop his films, which apparently makes it seem very bright and workable in a room lit by a safelight.

I suppose that wearing the red goggles before going out into a dark night with your dim red torch will also help the ability to see well from the start.


...I'm going off to buy some red goggles...!

Your eyes see with rods and cones. The rods detect light volume (black and white), the cones detect colors. The rods detect light by the destruction of a photopsin chemical called rhodopsin. Flash a bright light in your eyes and the spots you see are bits where the rhodopsin is now gone. Stay in the dark for a while and you build up a surplus of rhodopsin and your eyes are ultra-sensitive to light (night vision). Since the rods only see black and white, this is why things at night time look more like black and white rather than full color.

The reason red doesn't kill your night vision is that red's wavelength is below rhodopsin's light detection range. The cones still pick it up however, so you can see by red light. Since cones use photopsins as well, you can still blind yourself with bright red light (flash yourself with a red flashlight and you'll see red spots), but the effect is much less and goes away quicker. And since it doesn't destroy rhodopsin, your night vision is still OK. There are 3 types of cone photopsins, (L)ong, (M)edium, and (S)hort, which have peak sensitivities at 420nm (S, blue), 534nm (M, green), and 564nm (L, orange-red). Rods can only detect up to 580-600nm (and only dimly), and red's wavelength is 630-760nm.