Interview with a light researcher

„In the beer garden, we find a shaded resting spot“

The glitter of the Isar river, the clear light during foehn weather, the shimmer of the sun under the canopy of the beer garden chestnuts: the light in Munich feels special. Can it be scientifically proven too? An interview with Andreas Wojtysiak, who researches the light surrounding us for the Munich company Osram.

When Andreas Wojtysiak strolls along Munich’s Kaufingerstrasse, he is also attracted to the shop windows. But he doesn’t pay attention to the clothes or luxury watches on display. He is fascinated with how the goods are illuminated. Spotlights or floodlights? Direct or indirect light? At which angle does the light hit the object? Wojtysiak works as a light researcher. Together with his team at the Munich company Osram, he wants to discover how light makes driving safer, how crop growing works without sunlight – and how we bring light effects from nature into our offices and living rooms. The approach is called Human Centric Lighting. And the model is nature. So if anyone knows what makes the light in Munich special, then it’s Andreas Wojtysiak.


You have researched the light surrounding us in nature for a good ten years now for Osram in Munich. What makes the light in Munich so special?

If we all need light, then there are longer daylight hours in Munich than in Berlin. We are nearer to the equator. Therefore, we have longer days in the winter. This is obviously great for the inhabitants. However, for us researchers, Munich is simply representative of a central European city at this longitude and latitude. From a scientific perspective, we unfortunately cannot confirm the fact that there is a special light here.

So where does this special beer garden light in Munich come from? What ensures that this pleasant cosy atmosphere comes between the chestnuts and the benches onto the gravel?

People seek refuge in the beer gardens on warm, bright days. The trees above us provide shade, they filter part of the sunlight, in particular the short-wavelength light, which we humans perceive as bluish. This is the part that activates our bodies and keeps us awake! What’s left over under the trees in the beer garden is long-wavelength, red light. This appears in our eyes as warm and soothing.

Like the cosy light of a candle.

In the beer garden, we find a shaded resting spot. But at the same time, we see that it is still a radiant bright day outside of the beer garden. We feel like we are in a small protected haven – and like we are looking out onto the world.

If the blue parts of sunlight activate us, as you say – how come we often get so sleepy in bright sunlight?

If you lay in the sun for example on the banks of the Isar river, then you often have your eyes closed. So therefore barely any light reaches your retina. The stimulating effect of daylight is cancelled out. Added to this is the fact that it is exhausting to be out in the sun. It is hot, the organism increases and we start to sweat. So we therefore need a bit of rest.

Could we actually help you as a researcher by placing measuring instruments on the banks of the Isar river?

Unfortunately, that would bring us few new discoveries.

„We feel like we are in a small protected haven – and like we are looking out onto the world.“
Andreas Wojtysiak

What a shame!

That would surely be a great job. But we work with special light measuring instruments like a photometer. We make defined measurements with it and examine for example the amount of light that meets a certain surface area. A number comes out, the so-called light intensity, which we indicate in lux.

So how much lux does a foehn day have, one when we get a sudden urge to dip our feet in the Eisbach in the English Garden?

In direct sunlight, we measure up to 100,000 lux. For comparison, there is only 0.1 lux on the night of a full moon. And in order for it to feel light enough, we need a good 500 lux at our desks in an office. We therefore notice how much the eye achieves if it can deal with such crazy magnitudes. Humans can see in the dark of night and on very bright days.

Now you don’t just research light. You are also trying at Osram to use your knowledge in light systems.

Osram is developing concepts to do with light. In my field, Human Centric Lighting, we learn from nature and simulate light effects. We are always asking ourselves the question: which light do humans need at what time of day and in which location?

Why is this so important?

We often go to work and come home in the dark nowadays. We only see daylight from our place of work. This is the life of modern humans. We are increasingly retreating indoors – we have thus ceased evolutionarily going outside. In daylight. We humans are made to lead an active day.

,,We only see daylight from our place of work. This is the life of modern humans.''
Andreas Wojtysiak

How are you trying to help people?

We can produce light indoors, which imitate a beautiful day in the sun. The worst thing for the body is actually to be exposed to the same, let me say, “light soup” for the whole day. This neither stimulates our inner body clock nor our natural day and night rhythm.

In winter, the effects that you describe are even more pronounced.

The time, during which natural light shines, is shorter. However, our working days are just as long. We cannot cope with this. There are people who can suffer from light deficiency syndromes.

Do you mean the colloquially named “winter depression”?

It is genuine, it really does exist. Humans, who have a predisposition for this, can suffer from seasonal depression. We can fight these symptoms with Human Centric Lighting so that the timing of our inner body clock works better.

Let’s bring the discussion back to practice. We perceive the light that is reflected in the water of the Isar river or the small lake in the English Garden to be beautiful. Why is this?

This brings three things together. First: the movement of slow flowing water. We see for instance the Isar river flowing slowly and this calms us. Second: we never actually look directly into the sun, but often only see it in reflections on objects. On water for example as small glistening dots. We know this effect from the glittering of gems, when they are cut. The facets, these sharp points of light, which come into contact with our eyes on our retina. This fascinates us humans.

Video: spot on: spring

And the third thing?

A particularly clear body of water like the Isar river also provokes a positive reaction. It glistens particularly intensely on a smooth water surface with light waves. The more glistening points we see, the more beautiful it is. In the end, it is therefore the overall impression of sparkling, the clearness of the water and its slow flowing movement that we find beautiful in the Isar river.

About Andreas Wojtysiak

Researching the light that surrounds us - that's exactly what Andreas Wojtysiak does professionally for OSRAM. He is particularly interested in the concept of "Human Centric Lighting", which focuses on the biological effect of light on people.


Text: Niclas Seydack; Photos: Frank Stolle; Video: Redline Enterprises


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