TBone's Introduction to Human Vision at Low Light

so why wouldn’t dim green light be best for seeing in the dark and preserving night vision?

you said bright green light is bad but….

wle

I love this topic. I hope LED lights of the future will be able to change color as needed for certain task, tactical vs searching for example. How difficult would it be to develop something like that? With ramping for different tints?

ramping for tints? what kind of ui would you have? a phone app? touch screen on the flashlight?

there are lights with red leds included for night vision but of course it is very primitive, just select red or white, i guess red level is assumed to be low

wle

I’m sure that a light with multiple LEDs could be designed to ramp up certain tints and ramp down others, using multiple switches.

I’m hoping to give Toykeeper a challange :smiley: :wink:

The OP is apparently more well versed than most on this subject. Butt here goes with my take on it summarized……….

Bright anything tends to wreck night vision havoc on yer eyes - including oft used green. So if yer gonna use green keep it lit soft and low to optimize its inherent eye-friendly wavelength advantages.

Ask and ye shall receive :smiley: , i believe it may be implementated in the BLF lantern: *BLF LT1 Lantern Project) (updated Nov,17,2020)

The following quotes are from the first post of that thread which is looooong:

“Compact design based from the BLF Thorfire Q8 mid-section and battery section, with great run times, output, and tint ramping, mode groups, built-in USB charging capability, and versatility.”

“The firmware will be developed specifically for lantern use by Toykeeper of BLF, and will have most of the same mode groups as the Q8 flashlight, but with added modes including Candle-mode, sunset-mode, & possibly a tint ramping mode, (which allows the driver to ramp/fade between 3000K LEDs to 4000K LEDs, which will require a third lead for the LED star to have two channels, (one channel for three 3000K 3535 type LEDs and three 4000K 3535 LEDs, possibly the new Samsung High CRI LH351D-3535 series of LED emitters.”

Shrinking that down to EDC size can only be a small step away. :smiley:

According to the diagram you could use a very low green to keep your low light vision. But it depends on the brightness. If you use your flashlight to find your way, 2 to 3 meters ahead and swing your hand into the beam the reflection of your hand will temporarily blind your low light vision.
In this case I do not see the advantage over red light which should be inherently safe at any brightness.

So no matter if I shone a 1,000 lumen red light right into my eyes it wouldn’t/shouldn’t affect my night vision?

Actually red lights are used to preserve night vision/seeing in dark situations. That’s what Astronomy hobbyists like myself use and that’s also why you see them used in photographer “darkrooms” when developing film…for photographers not using digtial.

Ok understand that butt again there’s no affect on night vision no matter how bright the red light is?

Didn’t see your post when I typed mine :slight_smile:

No, it definitely matters. For Astronomy, the flashlights are kept very dim. 1/2 lumen is generally recommended. Many of the lights have variable adjustments and you turn the up just enough so white papers appear brown. If you can actually see a red spot, it’s considered too bright. It’s not horrible though.

Consider this: You need to sit in a fully darkened room or area for 20 minutes before your eyes fully adapt. One light ruins that. There’s a mythbusters experiment on this that was pretty darn good, which included the reason that Pirates wore eyepatches. It wasn’t because they lost an eye. It was to see belowdecks. They’d move the patch to their other eye once they were in the dark :slight_smile:

Yes, as I understand it. Even if my gut feeling says that being blinded always feels complete.

Common sense is not always up to date about non-natural stuff. Here we have almost monochromatic (single color) light.
In nature most light comes from glowing stuff with a wide spectrum. So you know when light heats up your skin it can give you sunburn.
Then came UV LEDs…

There may be some effect if red light triggers the closing of the pupil but his will be very temporary.
.

The best way to find out if bright red light is a problem for low light vision is the classic way: Go out in the dark with a red and a white flashlight and test it.

A possible reason why astronomers dim their lights as much as possible may be historical. Before LEDs existed they used red filters for incandescend light bulbs. Cheap filters do not block light of lower wavelength good enough so with more brightness you get more badly filtered light that will affect you low light vision.

I think there are two slightly different scenarios being discussed here: rod only vision, and vision with the cones engaged at high sensitivity (at which point the rods may or may not be working within their range of function.) My assumption is that most people’s experience with night vision is with the cones still engaged, which is a different discussion to rod only vision.

My guess is that if the red light only contained frequencies that cones can’t detect the cones wouldn’t react directly to the light, but the light might overwhelm the rods effectively blinding them. If you turned off the red light you would then need light of other frequencies bright enough to engage the cones above a level the rods are blinded at, or wait for your rods to regain their sensitivity again before being able to see.

Red light is used in photo darkrooms because it’s the frequency to which the photosensitive film reacts to the least. if you were too turn on a normal light it would make a photographers job a lot easier but ruin all the negatives through overexposure to light.

We have that red. It is called deep blue. :wink:

Great link to ‘handprint’ page, Djozz. Thanks.
— also trained as a biologist.

I recall the discovery of the fourth opsin receptor — the one that regulates sleep/circadian rhythm, without contributing to vision —- was done by searching for molecules similar to the three opsins that make up color vision.

https://www.google.com/search?client=firefox-b-1-d&q=circadian+receptor+wavelength

(that’s eight years old, likely there’s newer science to be found)

And unknowns persist:

Oh, and why LEDs and other blue-pumped fluorescent light sources are troublesome for babies and older people who have easily disrupted sleep:

So the LED makers are releasing LEDs that don’t emit in that critical blue-sensitive wavelength:

More at: LED advancements drive quality of light gains (MAGAZINE) | LEDs Magazine (interesting mention of how new LEDs fail to activate optical brighteners, which are explained here: Why Do Old Ladies Dye Their Hair Blue? – Rue The Day!)

If you compare apples to apples, a warm LED light source comparable with an incandescent 2700K bulb doesn’t emit much blue light either.

Yeah. This is why I want one of these ^.

A flashlight with dual red/white only makes sense. Sometimes you need to preserve your night vision.