Horological Meandering

Marcus Hanke
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Never underestimate the abilities of your built-in hard- and software ...

the human body is a miracle, and also the eyesight is a wonderfully complex and flexible system with unbeaten capability. The optical sensor consists of two different types, rods and cones. The cones are in use whenever there is enough ambient light. Cones can differentiate between various colours, but their sensitivity is limited. This is again the strength of the rods, which are able to sense even very low amounts of light, but are unable to see colours, other than black and white. The complex array of optical sensors in our eyes is coordinated by the brain, the software.

The brain is able to activate cones and rods, depending on the amount of light present, and to interprete the signals received from them. The great thing is that the brain is able to use the experience of a lifetime to "invent" or add information that is not perceived by the eyesight, but that should be there. Consequently, our brain is able to see a red shine even when only the rods are working, but when we know the light should be red, we "see" it red, not white. The same happens with the perception of a watch dial: Even if our optical sensors register only fractions of the dial, our brain adds the rest, because we know from daylight what it should look like. Therefore, we are able to recognize and read a watchdial at night, even if markers and hands emit only a very faint glow.

However, even this great system has weaknesses: The activation of the rods and the interpretation of their signals needs some time, which we use to call "to adapt to darkness". Whenever there is a large and dominating source of light, we have difficulties to recognize things in the shadows, or in the very dim light. Think of a cinema, or a theater: As long as the screen or stage is brightly lit, you will have massive difficulties to read a program folder in the darkness of your seating row without the help of a lamp. the same is valid for watch dials: At an ambient light situation like this, the faint glow of many luminescent elements is not strong enough to make itself visible; it is not bright enough to have the cones transmitting a usable picture of the dial, and not dark enough to permit the rods to see the glow.

Another problematic situation is the time between entering the darkness and receiving a usable signal from the rods, the time we need as "getting adapted to darkness". During this time we would not be able to recognize the luminous dials, if they are not bright enough.

This are the situations where the technical difference in the efficiency of the various luminscent materials becomes important: Watches with tinted SuperLuminova, be they red, blue or black, cannot emit enough light to permit a recognition during the adaption period or in dim light. Also watches with white C1 SL are unable to achieve a good result then, even if all of them are legible enough in the darkness of the bedroom, when one wakes up for a short while after hours of sleep, with the eyes being perfectly adapted to darkness.

Regards,
Marcus

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