Prof. Maciej Zajkowski: Leds do a milking job. You have to read with an old light bulb

Agata Savchenko

Prof. Maciej Zajkowski does everything he can to make artificial light as safe as possible. However, there is no doubt – nature is the best! That’s why he advises – instead of turning on the light bulbs – sit by the window or go into the garden and use what we have for free – sunlight

You are the lighting expert. Do you also have to deal with darkness?

Darkness in our lives is even more important than light. When we talk about light, we should always think about darkness.


For there is no light without darkness. The combination of light and dark is as natural as a combination of good and evil. To use light you need contrast. In order to perceive something, we must have dark and light. Only then will we see the details.

Your team explores this radiant reality. for what?

In the photometric darkroom we take light measurements, measurements on lighting equipment including: one used in indoor lighting, road lighting, stadium lighting or lighting architecture. We measure all the major parameters: we determine how much light a particular source produces, how much light, how it shines or evenly, is it safe to use, how much it can adversely affect a person through the so-called revelation. We also define the color of light, spectral distributions, ie which colors can be reproduced by such a source. We are trying to test these light sources so that they can be compared to sunlight and assess their degree of safety. Because sunlight is the ideal. It is best for humans, animals and plants.

So artificial light sources can be dangerous?

For example, too much light is dangerous, that is glare, the strength of which we can measure in our laboratory. The color of the light is a very important factor. We have known for years that blue light is harmful to us, but infrared or ultraviolet can also adversely affect our body. Such a deep, very aggressive, very energetic ultraviolet, ie UVC, is just as destructive as gamma rays or X-rays. It is of course not in the space around us, but we can create it artificially very easily. Therefore, we check whether this ultraviolet is present in available and commonly used light sources.

I come back to the glare. This word has good associations, but the enlightenment you’re talking about is probably not positive at all.

This is a very unfavorable phenomenon that we are trying to eliminate or at least significantly reduce by building new lamps and lighting equipment. Unfortunately it is very difficult. We can perceive glare if we look directly at the sun or directly at the light bulb. After closing our eyes, we briefly see a slice of light or the filament of the lamp, as if it had been burned onto our retina. And if we keep our eyes open, we can’t really see anything because we’re just overexposed. Such an unfavorable phenomenon can also be observed with some light sources.

How to properly adjust the light in the room?

You have to pay attention to both quantity and quality. There cannot be too much light – because then someone will be dazzled and not too little, because the conditions for working or reading are then too bad, or they cannot orient themselves in the room at all. There are standards in Poland that say, for example, to read we need 200-300 lux, and to work on a computer, there must be lighting of not less than 500 lux. In the absence of light, our visual apparatus, which consists of suppositories and rods, begins to tire. The stamens can distinguish colors, but need a lot of light. But on the other hand, if I turned off the light in the darkroom right now, we wouldn’t see anything for a while. In the blink of an eye, however, it would appear that we can recognize the objects present here. But we would see the shapes themselves, not colors. It is said that all cats are gray at night. And it’s true, because without light we only recognize grayscale. This is where the second cells in our visual apparatus, ie the rods, work. When there is not enough light, our brains tire much faster, causing fatigue throughout the body.

You also mentioned the quality of the light.

We often say that we have trouble sleeping because we use cell phones, laptops, computer monitors, televisions. Moreover, nowadays we almost exclusively have modern LEDs everywhere. And these modern LEDs unfortunately do a great job.

Why is this blue light so bad?

It inhibits the secretion of melatonin. And the lack of melatonin in the body causes sleep disturbances, which in turn cause serious health problems. That’s why we fight this problem so much, we try to build these devices in a way that eliminates excess blue light. Unfortunately, we won’t reduce it completely. That’s a shame, because we’ve completely forgotten what the body’s daily cycle is. For millions of years, our bodies have become accustomed to seeing the sun rise red in the morning, then bluish during the day, and red again at night. This causes melatonin levels to fluctuate in the same way. The more red light, the more melatonin. The more blue there is, the less melatonin and more cortisol. Cortisol stimulates us – that’s why we work, move and do many important things during the day, and in the morning and evening our bodies go to sleep. Today we do the exact opposite. We try to extend the day. We provide as much artificial light as possible, we have no control over natural light.

But let’s make a deal – we have too many daily tasks to get everything done before the sun goes down. We usually rest in the dark: behind the computer, tablet, smartphone… Would a traditional book or newspaper be a better solution?

If we have LED lighting in the house and we read the newspaper with it, we still have a blue light attack. So if we want to read, let’s read with old light bulbs, with old halogens. I know, they’ve already escaped our lives, withdrawn from the market, uneconomical, but… healthier.

What if we don’t have such lamps yet?

Let’s read this by the window or in the garden…

Probably on vacation alone! Who has time today to read in the garden in daylight…

Yes. In any case, let’s do it on vacation. And every day we should try not to expose ourselves to this blue radiation at least half an hour before going to sleep.

Are there specialists in Poland who can be asked to advise ordinary people which light to install in which room?

Virtually every one of us is a lighting specialist these days. Because if we like a lamp, that means it’s good, right? We don’t realize that even what’s so fashionable and modern can pose far more problems than benefits. And when it comes to specialists, let me be honest: there are very few people in Poland, and very few in the world, who have to deal with such strict technology and light measurements. Here, at Białystok University of Technology, we are creating one of three such teams in Poland. We try to show you how to light, how to use lighting wisely and energy-efficiently – because it is also very important to pay little for lighting. Fortunately, in this case, education is so well prepared that everyone has to deal with it. Elements of the use of light occur in both primary and secondary education, especially in physics classes. However, the fact is that today almost all electricians who design installations, ie sockets, switches, lamps, have basic knowledge about efficiency, but little about the quality of the world.

Give the most important rules to follow when designing light in our environment.

It pays to have a reading lamp with an old light bulb in at least one place in the house. In other cases, you know, we have to save, because energy is expensive, so we use modern LED sources. Fortunately, they are actually of better quality. Still, we won’t eliminate the blue light problem 100 percent, so we just have to get used to it. An important rule to follow is that we make the most of daylight. And when the sun goes down, let’s use electricity, of course. In the living room – where we read, talk, watch something, we should have a little more light than, for example, in the hallway, bathroom or kitchen. But on the other hand – the light in the kitchen must also be of good quality. Because dishes are not only about taste, smell, but also appearance. The quality of the lighting is also important in bathrooms, where ladies do make-up. The LEDs slightly distort the perspective of color vision. As a result, the face in the bathroom looks completely different than in daylight. It is worth using halogen lamps next to the mirror in the bathroom. And if this is not possible, choose the best quality LEDs.

How do you recognize this good quality?

You must read the parameters on the package. First of all, pay attention to the CRI marking – the closer it is to the hundreds, the better the quality of the light. However, it should not be lower than 80. When it comes to energy savings, we look for the abbreviation LM / W – it means how many lumens we have from one watt. Here the value must be at least 80 and higher, so for example 100, 120, 150. The higher the value, the better the light quality and more economical. As for the radiation quality, we look for the CRI or Ra parameter. The closer it gets to a hundred, the better. An ordinary incandescent lamp has exactly 100, LEDs have 80-85, rarely 90. And how many of these light sources should there be in a given room? Strict regulations and standards apply here for lighting in public buildings, hospitals, offices, schools, but also the standards require good lighting of roads, pedestrian crossings, parking lots and even sports facilities. And at home, let’s just try to make ourselves comfortable. Every room is slightly different, has a different shape, even the color of the walls allows us to recognize light differently.

Is there a chance that scientists will invent an incandescent, fluorescent, or other source that will shine in the same way as the sun?

They’ve already figured it out. It is available, but very expensive.

But is it worth investing in?

It is worth investing if accurate color recognition is important in our lives. For example, computer graphic designers, people who work with textiles and in general with printed color must have very good quality light. And on a daily basis… It’s worth going outside, sitting by the window and using what we have for free, which is natural sunlight.

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