Of cones and rods – the perception of light.

How many lumens do MICROFLOOTER and ATON emit?

We’re often asked what the lumen value of our MICROFLOOTER and ATON auxiliary headlights is. This is a good question on the surface, but the answer only reflects half the truth because the lumen value alone only ‘shines a light’ on one aspect.

Alongside the individual value of light emitted by the bulb, which is given in lumens, there’s also another, equally important aspect that we need to take into account: the sensitivity of the human eye to the perception of light, which is explored and studied within the context of perception physiology.

Perception of light

The so-called photoreception of light – that is, the ability to perceive light with the human eye – is limited to the light spectrum between 380 nm (violet light) and 640 nm (red light). The ultraviolet (UV) range begins below 380 nm and the infra-red (IR) wavelengths begin above 640 nm. We humans cannot see or perceive the UV and IR ranges. In the truest sense, we are blind to these wavelengths because we don’t have the receptors to perceive them. The spectrum here ranges from blue, which we perceive as cold, to red, which we perceive as warm light.

Furthermore, there is a distinction between day, night and twilight vision, with different receptors being responsible for each one: the so-called ‘cones’ in the retina are responsible for day vision and the more light-sensitive rods are responsible for night vision. At twilight, both cones and rods are responsible for perceiving light.

The rods responsible for night vision are not only more sensitive to light, but are also more sensitive to blue, cold light, i.e. the portion of the light spectrum with shorter wavelengths. This is why we often perceive moonlight as being tinged with blue, for example.

The crux of this understanding is that it makes sense when designing an auxiliary headlight for night-time use to choose shorter wavelengths that emit blue, cold light in order to noticeably assist the human eye with light perception.

Summary

This brings us back to the beginning: naturally, a higher lumen value is always preferable. However, in every instance it is worth taking into account our knowledge of the physiological perception linked to sight and thus to design the spectrum of light emitted in an appropriate way. In the case of the MICROFLOOTER and ATON, we therefore opt for short-wave, blue light, which helps with high-contrast vision at night.

What's more, the value of the light emitted by our MICRO­FLOOTER and ATON auxiliary headlights falls within the range of approx. 1000 lm (lumens).

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