TBone's Introduction to Human Vision at Low Light

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.
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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.

DW3R1 DW3R1 - YouTube

Just playing.

Did you make that? What would be the cheapest way to convert one of my SK68 clones to a red LED ( >625nm wavelength) ?

These red SK68 clones on Amazon claim 200 lumens for $8.99 … so it’s probably about 20 lumens.
https://www.amazon.com/WAYLLSHINE-Scalable-Range-Flashlight-Detecting-Black/dp/B0136RV4YY/ref=sr_1_13?keywords=red+led&qid=1549759875&s=gateway&sr=8-13
But still, is that a pretty good deal or could I mod one of my existing $2 SK68s with a better/brighter red LED for less than $7?

One of the cheapest ways to convert your SK68 lights to a red light would likely be using this from mtnelectronics. Just make sure to double check the size of the emitter’s MCPCB in your light. It should be some straightforward pretty easy soldering.

If you are comfortable with emitter reflowing, you could get one of these . It’s one of the so called far red or deep reds. It makes the typical red lights you see around us look almost orange.

The main drawbacks I see to that SK68 clone on Amazon, is the real lack of useful U/I. A ramping U/I like Crescendo or the 17mm Moonlight Special from MTN would provide allot more flexibility and usefulness in a low light environment/night vision preserving situation.

I used the deep red for my mod. Guessing red is about 70 lumen driven with one 7135 chip.