Dark-Adaption is a human super-power that allowed humans to survive long before portable lighting became commonplace. Some animals have more powerful versions of this capability, but they usually give up some of their color perception in trade.
Normal human eyes can use light for vision over a 1 : 10,000,000 intensity range, or more. Your low-light scotopic vision (using mostly your eye's rods) can permit very-low light illumination intensities to be used while seeing most what is around you. But, there are ways using special spectra that can enhance your dark-adapted vision capabilities.
When you are dark-adapted and using your eye's rods and cones together (mesopic vision) you've enabled vision at ~1000X lower illumination than Photopic vision (using only your eye's cones). This means you can perceive far more visual information in your periphery and far into the distance even at low lighting, and not just in your narrow flashlight's main light beam's ANSI cones-only vision range.
In our light polluted world, many people seldom let their eye's rods activate. The eye's rods shut off seconds after even looking at a nightlight. Unless you are one of the few people that get out and away from the urban sprawl. Your rods are 100X as light sensitive as your eye's cones, and you have 20X as many rods as cones. Your rods are most sensitive to mid-cyan spectral light (490-505nm).
Nulumina provides several low-light vision modes in portable lighting to enable your mesopic vision, in addition to providing high detail and full-color range photopic vision capability modes.
Your 3 Vision States:
1. Photopic Vision is when you are only using your eye's 3 type color cones in medium- low to high luminance situations.
2. Scotopic vision is when you are only using your eye's rods in low to very-low luminance situations.
3. Mesopic Vision is when you are only using your eye's rods and cones together in medium-low to low luminance situations. This state of vision also allows very-low luminance Scotopic vision in portions of your visual field of view, and color vision elsewhere if the spectra of your illumination source (e.g., headlamp, flashlight, or moonlight) permits.
Stages of dark-adaptation after leaving average clear daytime ambient lighting:
Typical noticeable effect to near-complete transition - Change in responsiveness of vision
1-60 seconds - Pupils begin to dilate to let in more light (1X to over 10X range)
1-10 minutes - Color cones (all 3 type spectral range cones, ~ 6 million total cones per eye) increase responsiveness (1X to ~1000X range)
10-40 minutes - Rods slowly activate (Only on for vision in low light, ~120 million per eye) can increase light responsiveness by another ~1000X. Rods are most sensitive to cyan spectral light
Using Mesopic Vision
Rods and cones can work together in low intensity, "broad-spectrum" light. This is called the "mesopic" vision range. When dark-adapted in this illumination range, you can see colors and have your rods functioning to detect the most light, and your rods enable you to see far away or objects illuminated at over 10-1000X far greater distances than when you were not dark-adapted (visual distance range depends on spectrum, light intensity, beam angle, your level of dark-adaption, atmospheric conditions, surrounding objects, and the characteristics of the objects being illuminated).
You can use your mesopic vision with CYRAD illuminators in their lowest power modes to stretch battery life, but also see more of your surroundings. We took care to create CYRAD to enable excellent mesopic vision, unlike other headlamp or flashlight makers. This allows you to become a less obtrusive part of the nighttime world. See more wildlife or the milky way.
Nulumina CYRAD illuminators were designed with special modes to give you an opportunity to take best advantage of your dark-adapted vision. But, also give you the option to just use high power modes and blast the dark away for photography, or for maximum color & detail.
Also, Reflected light from illuminated objects and lens/object scattered light also can greatly open up your periphery and expose shadows if the proper spectra and system optics are used for your portable lighting.
About cyan spectral light: Cyan spectral light (~480-505nm) is very weak in other white LED headlamps and flashlights. We tested over 100 popular headlamps and flashlights. All these provided under 20% of the peak relative cyan spectral intensity at 490-505nm. This greatly limits your ability to see motion in your periphery and to effectively illuminate objects ahead at long distances when you are dark-adapted, yet the excess green and yellow spectral light makes shutting down your rods due to over-exposure a high risk.
Few headlamp and flashlight makers give much consideration to dark-adapted vision since "lumens" on the spec sheet does not apply to dark-adapted vision and few people know the importance of this parameter.
There is a scotopic (eye's rods)/photopic (eye's cones) vision merit parameter (S/P ratio) that for Nulumina Cyradiance LEDs is an excellent ~2 value. Any higher S/P value would compromise the Cyradiance's photopic true-color capability that is much better than other flashlights and headlamps.
There is also a formal dark-adapted brightness perception merit parameter. Cyradiance is actually brighter here than other similar power white light LED lamps, in addition to outputting the same or greater amount of light power per watt of your battery power than almost all other LED headlamps and flashlights.
FYI: Cyan-wavelength spectral light is different from cyan-color light made by mixing green and blue light together like in TVs or phones that output almost not actual cyan spectral light but still can appear cyan color to your eyes cones. You want true cyan spectral light to optimize your eye's rods visual response using minimal power. True cyan spectral light photons can be 10-40X more detectable by your rods than green-blue light mixtures!.
Cyradiance was created to enable a great balance of true-color and dark-adapted vision!
The Owlsight Headlamp and CG2 Flashlight ActiveRed filters and Mode-2 on the LEGLIGHTS are super for getting dark-adapted with mostly red light, but also output just enough broad spectrum light to show many important details.
Intense red light can be used up close because it minimally risks turning your rods off, but you are limited to photopic vision and monochrome red/gray with most red light sources.
The precise, but small amount of blue-cyan-green-yellow-orange light plus ALL the visible red wavelengths in Nulumina's "night vision red" spectra lets you see far more detail than red LEDs that effectively output only about 1/4 the visible red light spectrum can provide.
Plus, Low-power Cyradiance modes can be great for dark-adapted vision without a red tint. But, you must be more careful when using even these lowest power white-light modes to not shine the light on highly reflective or almost-white surfaces up-close, or your dark-adaption may need to restart (typically closer than 6 ft, see the individual product manuals).
We intend to add more detail about dark-adaption in this website in the future.
Each Precision Illuminator comes with a manual that includes quick start instructions on a few ways to quickly use your CYRAD for normal or dark-adapted vision.