HOW TO USE LIGHT METER FOR PLANTS?

Let's talk about light meters and how they can help us measure light for our houseplants. This video is part of a broader course on light for houseplants. So if you want to learn about natural light, grow light, or what we mean when we say direct versus indirect light, make sure to read the description for the video so you know how to join and you can participate in the course. But now let's talk about light meters. So what does a light meter actually measure? Of course it measures light, but there are many units to measure the same light. So let's look at the most common ones so we can understand a little bit better how this light meter works. The first one is aluminum. And aluminum in a nutshell is the brightness of one candle. Then we have a foot candle. And this is going to measure the brightness that falls into a light surface of one square foot from that same source of light, which in this case is the same candle. So just to put it visually, we're going to have a candle and then we're going to measure the light around that candle one square foot from that candle. The next unit is a lux. And it's very similar to the foot candle, but in this case we're measuring the brightness that falls into a one square meter area from that candle. And the last one is a PAR. Now this is a little bit different and I'm going to explain why. When we talk about a foot candle or a lux, we're measuring in lumen. And lumen is very close to what we perceive with our human eye. In the light spectrum, we perceive green and yellow more than blue and red. So if you look at it in the graph, you're going to see a bell shape where green and yellow are in the center and blue and red are on the sides. Because our human eye is more sensitive to yellow and green in the light spectrum. However, plants perceive And the PAR is going to be sensible to all colors equally as well. So as you can see in the graph, instead of a bell, we have a square. So all of the colors are perceived equally, just like the plant would perceive them. Now does this mean that we can only use PAR to measure light for a plant? No, not at all. PAR is one way to measure light, but we also have lux and foot candles. They're different ways because of color sensitivity. So while PAR is more sensible to all of the colors equally, a foot candle and a lux, which use lumens to measure light, will be less sensible to blue and red, more sensible to green and yellow. So when we're using these units, we just want to make sure to understand which unit we're looking at and what numbers we want to see depending on the unit. A very good example to show this in another area of our life is when we're baking. You know, we can measure temperature in Celsius or in Fahrenheit. So when we're baking a cake, we want to make sure that we understand which unit we're using. If we're using Celsius or Fahrenheit, so we understand which temperature to put in the oven. Okay, now let me show you how to use a light meter with your plant. So how do we use a light meter? As you can see, my light meter here measures using lux. So in general, our plants will be happy with 2500 lux to 4500 lux. Of course, this is a very general guideline and I recommend that you get to know your plant and see what is best for her. And just to let you know, if you join the course, I also have included a PDF list with the most common houseplants and their light requirements. So do make sure to check that out. In general, we're going to want to have 2500 to 4500 lux. And I'm going to show you how to measure the light. So let's get to the plants. Very important to remember, we want to measure the light at a point in the day when we cannot see the sun from where we're standing. So our plants can see the sky, but not the sun. This is because we want to measure indirect light and not direct light. So measure when your plant can see the sky, but not the sun. And the way that we're going to measure it is we're going to open this here, turn on our light meter, and place the sensor on top of your plant. As you can see here, the light is just above the 2000 lux. And this is because today we have a very cloudy day, so we don't have so much sunlight. It is also cold in Berlin. So now I understand my plants really need to be very close to the window. Because here, right in front of a window, of a south-facing window, right now they're getting just below what they would even like in a minimum, which would be 2500 lux. So yeah, this is very good information as you can see. And as you can see, these plants are actually standing right in front of a south-facing window. In the summer, we get lots of sunlight here. So some of them cannot even stand so close to the south-facing window. But now that we're in October, we don't get so much sunlight, because as you can see, it's super cloudy today. So yeah, this is a life changer. Now I can tell you that this also helped me see how much light actually decreases when you get away from the window. And this was really incredible, because I have an asparagus fern just one meter away from the window, and I'm going to show you how much light actually decreases with them. So again, this is the light that my plants actually get right in front of a south-facing window in October here in Berlin. Now let me show you how much light decreases if you move away from the window. This is where my asparagus fern is, and look at that. Even if I put it towards the window of the sensor, let's see, one hand is a little bit, oh, yeah, like so. Look at that. It is about 400 lux, whereas over there, they actually get 2000 lux, and it's only one meter away, you guys. That's incredible, no? So now I know that this asparagus fern, at least today, is not getting so much sunlight, and it's not getting maybe even enough light for their growth. I can tell you my light meter has helped me so much understand my plants a little bit better, and also understand light from their perspective, which makes me feel more connected to them and way more equipped to actually help them thrive. So I would strongly recommend that you get a light meter. If you want to check out this one for yourself, I will put the link in the description down below so you can check it out, and also make sure to check out the course. We go way deeper into light, grow lights, and just anything that has to do with light so you can understand it a little bit better from the plant perspective and help your plants. So I hope that you join us there and as always, I will see you in the next one. Okay, adios!