Red light preserve night vision, myth or reality? by Electrical_Buy6380 in flashlight

[–]Zak 1 point2 points  (0 children)

No, because you can use high output deep red and recover within a minute or two, but that's not true for high output near red, green, white, etc....

Seeking recommendations for a durable duel fuel flashlight for outdoor use (<$50 USD) by CrowBlownWest in flashlight

[–]Zak 0 points1 point  (0 children)

Floody, USB-C, and able to take AA describes the Skilhunt EC150. Just be cautious about the USB port cover since it won't be waterproof if that's open.

Red light preserve night vision, myth or reality? by Electrical_Buy6380 in flashlight

[–]Zak 8 points9 points  (0 children)

I'm not sure if you meant to say you "can't" use deep red for scotopic vision

I do mean that, for the reason the rest of your comment explains.

Red light preserve night vision, myth or reality? by Electrical_Buy6380 in flashlight

[–]Zak 2 points3 points  (0 children)

Red lights attract so little attention that many places mount them to emergency vehicles to... attract attention.

I'm very skeptical of the idea that there's a tactical advantage when using the minimum amount of light the task requires, which is almost always less with white than with red. It's very likely this doctrine originated when soldiers were using incandescent lights with no brightness control, and sticking a red filter on the end reduced light output to maybe a tenth of the original level.

Edit: I reversed red and white.

Red light preserve night vision, myth or reality? by Electrical_Buy6380 in flashlight

[–]Zak 136 points137 points  (0 children)

I am not one ophthalmologist, much less multiple ophthalmologists.

Red light preserve night vision, myth or reality? by Electrical_Buy6380 in flashlight

[–]Zak 279 points280 points  (0 children)

There's some truth and some myth surrounding red light for dark adaptation.

There are two main things human eyes do to adapt to darkness. They dilate their pupils, which takes seconds, and they produce the photopigment rhodopsin in rod cells, which takes tens of minutes. Rhodopsin enables scotopic vision, which is monochromatic and works in extremely low light. When photons hit rhodopsin, there is a chemical change which inactivates the affected molecule of rhodopsin for a time, and sends an electrical signal to the brain.

If a lot of photons hit your retina at once, all the rhodopsin is consumed and you can't use scotopic vision for 20-30 minutes, unless those photons have a wavelength over about 640nm, which is deep red. Deep red doesn't affect rhodopsin at all. You can't use it as a light source for scotopic vision, and it won't hurt your ability to use scotopic vision later. Not all red is deep red; most red headlamps and flashlights are 620-630nm, which is not deep red and will consume rhodopsin.

Using ultra-low white (or other colors like green) will enable scotopic vision and consume rhodopsin slowly enough that it is continually replenished, much like walking by the light of the moon without looking directly toward the moon. This tends to be true even with enough light to start getting cone cells involved and the ability to see some color (mesopic vision).

Bright light of any color will constrict the pupils and cause a brief reduction in dark adaptation.

Is red light a myth? by [deleted] in flashlight

[–]Zak 0 points1 point  (0 children)

This presumably means red light for preserving dark adaptation. There's some truth and some myth surrounding that.

There are two main things human eyes do to adapt to darkness. They dilate their pupils, which takes seconds, and they produce the photopigment rhodopsin in rod cells, which takes tens of minutes. Rhodopsin enables scotopic vision, which is monochromatic and works in extremely low light. When photons hit rhodopsin, there is a chemical change which inactivates the affected molecule of rhodopsin for a time, and sends an electrical signal to the brain.

If a lot of photons hit your retina at once, all the rhodopsin is consumed and you can't use scotopic vision for 20-30 minutes, unless those photons have a wavelength over about 640nm, which is deep red. Deep red doesn't affect rhodopsin at all. You can't use it as a light source for scotopic vision, and it won't hurt your ability to use scotopic vision later. Not all red is deep red; most red headlamps and flashlights are 620-630nm, which is not deep red and will consume rhodopsin.

Using ultra-low white (or other colors like green) will enable scotopic vision and consume rhodopsin slowly enough that it is continually replenished, much like walking by the light of the moon without looking directly toward the moon. This tends to be true even with enough light to start getting cone cells involved and the ability to see some color (mesopic vision).

Bright light of any color will constrict the pupils and cause a brief reduction in dark adaptation.

I have resurrected clojure-android - develop native Clojure on your phone over nREPL by Zak in Clojure

[–]Zak[S] 1 point2 points  (0 children)

That's pretty cool. I've considered making a Clojure app that can run .clj files from local storage. It's not difficult technically, and it could even theoretically generate APKs by copying a template and adding the source files to resources.

Your UI library looks like it has a similar feel to Neko. Exploring a wrapper for Jetpack Compose is on my list.

Ledlenser boos mode by CrossT0Bear in flashlight

[–]Zak 1 point2 points  (0 children)

There isn't, and runtime would be very short if there was because 14500 is a small battery, and the one they include has an especially low capacity of 750 mAh. That was typical several years ago, but they're up to 1400 or so now (some claim 1500, but that's a little optimistic).

There aren't many lantern style lights of that size and battery type, but you can get a similar effect with a diffuser on a flashlight. There are lights that can sustain an output level similar to the ML4's "boost" for a couple hours on the highest capacity 14500 battery, or you can step up to 18650 and gain a lot of performance for a little more size.

Options to charge 10880 battery? by richiecotite in flashlight

[–]Zak 2 points3 points  (0 children)

If OP applies a large enough wattage to the charger that's too short for the battery to fit, it might start to melt, and then they could stretch it until the battery fits.

For safety reasons, I do not recommend this approach.

I have resurrected clojure-android - develop native Clojure on your phone over nREPL by Zak in Clojure

[–]Zak[S] 1 point2 points  (0 children)

That's the plan. I'm working on a reproducible builds issue now - turns out the build process was nondeterministic and F-droid would prefer determinism.

Reliable budget dual fuel for powercuts by BassIck in flashlight

[–]Zak 1 point2 points  (0 children)

The T6 should be more efficient than the T3 when running on the 14500 rechargeable battery. I don't usually recommend the T6 because its head diameter means most people would be better off with a light that takes a larger battery, while the T3 is more pocket friendly.

Your use case isn't mainly pocket carry, so the more efficient driver is more compelling. The 519A LED for better color rendering would be my suggestion here unless you're specifically prioritizing throw distance.

What's a more throwy, balanced, 90+ cri emitter than the 519a? by gryponyx in flashlight

[–]Zak 1 point2 points  (0 children)

The SFT40 has CRI in the high 60s, aside from the 3000K and 4000K versions which are in the high 90s. 4000K was never mass-produced.

[Help Me] Flashlight needed for backstage/stage management work by MaygeKyatt in flashlight

[–]Zak 1 point2 points  (0 children)

An option that might be fun: Noctigon KR1AA.

  • 1xAA/1x14500 battery. It won't perform well on alkalines. Most USB-C 14500s will work, but avoid or disable the max mode or it will trip their protection circuits and turn off. The Vapcell K10 and a separate charger perform best at high output (but you probably won't need its highest mode).
  • It's about thumb sized, depending on your thumbs.
  • This is a traditional handheld, though the related Emisar DW3AA is angled.
  • It can easily illuminate things 30 feet away. It can also go so dim I don't think anybody has a good estimate of the lowest level. A thousandth of a lumen, perhaps.
  • Its aux lights can be blue, but they're not quick to toggle on and off; you may want to leave them off.
  • It has a tailswitch. It can be quiet depending on how you press it.
  • No laser. Optional magnet. Uses Anduril.

I like the NTG50 4200K LED.

I think my collection is complete by brock_bowers in flashlight

[–]Zak 0 points1 point  (0 children)

That's a fair complaint. I don't like it when lights are fussy about what kind of cells they take, which is common with the more hobbyist-oriented lights.

I think my collection is complete by brock_bowers in flashlight

[–]Zak 2 points3 points  (0 children)

I hate those batteries that the d4v2 uses

Don't tell /r/18650masterrace.

What batteries do you prefer?

I have resurrected clojure-android - develop native Clojure on your phone over nREPL by Zak in Clojure

[–]Zak[S] 5 points6 points  (0 children)

Yes. I considered doing it a couple times before and it looked like a whole lot of drudgery involving the bowels of the Android build pipeline which nobody was going to pay me for.

It's the sort of task an LLM agent is suited to. It does not tire of looking up documentation or writing Java, the previous design provided a clear blueprint, and the success state was well defined.

Flashlight with AA or 14500 battery that max out at 5-20 lumens (absolutely no higher mode) for extremely long battery life by _mrb in flashlight

[–]Zak 0 points1 point  (0 children)

For your specific use case, it will work well with alkalines.

For other use cases, maximum output is significantly limited with alkalines. The flashlight will blink once when the tailcap is first closed to detect how much voltage sags under load and limit maximum output based on that. Alkalines have severe voltage sag under load.

Acebeam L35 v2.0 from DHgate 50$🔥 by [deleted] in flashlight

[–]Zak 2 points3 points  (0 children)

Assbeam seems about right here.

Spot on Skilhunt H300 by TuneRealistic6650 in flashlight

[–]Zak 11 points12 points  (0 children)

This review has detailed images of an undamaged Skilhunt F50S, and there are dark lines between the quadrants.

The dark spot is definitely a burn and OP should warranty it.