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.
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.
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 suck at soldering, or maybe the problem is my iron barely gets hot enough to melt the solder; but in any case, I’m gonna get the one from fasttech. $4.11 with free shipping is a deal.
