Monika Zagrobelna - Improve Your Artwork by Learning to See Light and Shadow

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Learning to See Light and Shadow

Text of Monika Zagrobelna - Improve Your Artwork by Learning to See Light and Shadow

  • Improve Your Artwork by Learning to See Light and Shadow Monika Zagrobelna

    It's very common for painting tutorials to treat light as an addition to the picture, an atmosphere-maker. We can easily get the impression that the object has a universal form, and then with proper lighting we can change the mood of the picture. The truth is without light there would be nothing to paint! Until you realize that, you're shooting blind.

    In the first tutorial of this short series, I'll introduce you to the art of seeing light, shadows, reflections and edges.

    How Can We See?

    As an artist, have you ever tried to answer this question? If not, that's a big mistake. Everything you draw is a representation of seeing, just like the laws of physics are a representation of real processes. There's even more to itwhat we draw is not reality, or an objective image of reality. It's an image created by your brain, an interpretation of signals caught by your eyes. Therefore, the world as we see it is only an interpretation of reality, one of manyand not the truest or most perfect of them all. Only good enough for our species to survive.

    Why am I talking about this in a painting tutorial? Painting itself is an art of darkening, lightening and coloring certain parts of paper (or screen) to create an illusion of looking at something real. In other words, an artist tries to recreate an image that could be created by our brain (it makes it easy for us, since we think in patternswe tend to look for familiar shapes in abstract pictures).

    If a picture is similar to what we see in our minds, we say it's realistic. It may be realistic despite not having any recognizable shapes or outlinesall you need are a few patches of color, light and shadow to bring something familiar to mind. Here's a good example of this effect:

  • Winter in the forest by Piotr Olech

    To create a convincing picture similar to one created by the brain, first you need to know how the brain does it. When reading this article you'll find most of the processes quite obvious, but you may be surprised at how closely science can relate to painting. We tend to see optics as a part of physics, and painting as a part of metaphysical art, but that's a mistakeart is a reflection of reality seen through our eyes. In order to imitate reality, first you need to know what our minds find real.

    So What Is Seeing?

    Let's go back to the fundamentals of optics. A light ray hits an object and bounces to your eye. Then the signal is processed by your brain and the image is created. That's pretty well-known, right? But do you realize all the consequences that stem from that process?

  • Here comes the first, the most important rule of painting: light is the only thing we can see. It's not an object, not a color, not a perspective, not a shape. We can see only light rays, reflected from a surface, disturbed by the properties of the surface and our eyes. The final image in our head, one frame of the never-ending video, is a set of all the rays hitting our retina at that one moment. This image can be disturbed by differences between the properties of every rayevery one of them comes from a different direction, distance, and they may have hit a lot of objects before hitting your eye last.

    That's exactly what we're doing when paintingwe imitate rays hitting different surfaces (color, consistency, gloss), the distance between them (the amount of diffuse color, contrast, edges, perspective), and most certainly we don't draw things that don't reflect or emit anything to our eyes. If you "add light" after the picture is almost done, you're doing it wrongeverything on your painting is light.

    What is Shadow?

    To put it simply, shadow is an area untouched by direct light. When you're staying in shadow, you're not able to see the source of light. That's obvious, right?

  • The length of shadow can be easily calculated by drawing the rays:

    Drawing shadows may be a little tricky though. Let's take a look at this situation. We've got an object and a big light source. Intuitively, this is how we draw the shadow:

  • But wait, this shadow is actually cast just by a single point on the light source! What if we choose some other point?

  • As we can see, only point light creates a sharp, easily defined shadow. When the light source is bigger (more scattered), the shadow gains a blurry, gradient edge.

  • The phenomenon I've just explained is responsible for supposedly multiple shadows coming from a single light source too. This kind of shadow is more naturalthat's why pictures taken with flash look so sharp and odd.

  • Ok, but that was just a hypothetical example. Let's take a look at this process in practice. Here's my tablet pen stand, photographed on a sunny day. Can you see the weird double shadow? Let's take a closer look.

  • So, light comes from the left lower corner, roughly. The problem is it's not a point light, so we don't have the nice, sharp shadow that's the easiest and most intuitive to draw. Drawing rays like this doesn't help at all!

    Let's try something different. According to what we've just learnt, a big, scattered light source is made of many point light sources. When we draw it like this, it makes much more sense:

  • To explain it more clearly, let's obscure some of the rays. See? If not for these scattered rays, we'd have a pretty normal shadow!

  • No Seeing Without Light

    But wait, if light doesn't touch the area, how can we see something that is in shadow? How can we see anything on a cloudy day, when everything is in the shadow of the clouds? That's the result of diffused light. We'll talk more about diffused light throughout this tutorial.

  • Painting tutorials usually treat direct light and reflected light as something totally different. They may tell you there's a direct light that makes surfaces bright, and that reflected light may occur, giving a bit of light to the shadow area. You might have seen diagrams similar to the one below:

    This isn't completely true, though. Basically everything you see is reflected light. If you see something, it's mostly because light has reflected from it. You can see direct light only if you're looking directly at the light source. So the diagram should look more like this:

  • But to make it even more correct, we need to bring in a few definitions. A light ray hitting a surface may behave in a few ways, depending on the kind of surface it is.

    When a ray is reflected fully by the surface at the same angle, it's called a specular reflection.

    If some of the light penetrates the surface, it may be reflected by its micro-structure, creating a disturbed angle resulting in a fuzzy image. This is called diffuse reflection.

    Some of the light may be absorbed by the object. If an absorbed ray manages to get out, it's called transmitted light.

  • For now, let's focus on the diffuse and specular reflection only, since they are very important to painting.

    If a surface is polished and has a proper, light-blocking micro-structure, a ray hitting it will be reflected at the same angle. Specular reflection creates a mirror effectnot only direct light is reflected perfectly, the same happens to the "indirect" rays (moving from the light source, bouncing off an object, and hitting a surface surface). An almost perfect surface for full specular reflection is, of course, a mirror, but some other materials give a good effect too (metal and water are examples of this).

    While specular reflection creates a perfect image of the reflected object thanks to the correct angle, diffuse reflection is far more interesting. It's responsible for color (we're going to talk about this in more details in the next part of this series) and it lights up the object in a softer way. So, basically, it makes an object visible without burning your eyes out.

    Materials have various factors of reflection. Most of them will diffuse (and absorb) a huge part of the light, reflecting only a small part as specular. As you probably already guessed, glossy surfaces have a higher factor of specular reflection than matte ones. If we look at the previous illustration once again, we can create a more correct diagram for it:

  • When looking at that image, you may be under the impression that there's only one point on a glossy surface where specular reflection occurs. That's not completely true. It occurs wherever light hits the surface, but there's only one specular ray hitting your eyes at a time.

    Here's a simple experiment you can do. Create a light source (use your phone, or a lamp) and place it so that it lights up a shiny surface from above and creates a reflection. It doesn't need to be a very strong or vivid reflection, just make sure you can see it. Now take a step back, looking at the reflection the whole time. Can you see how it moved? The closer to the light source you are, the more acute the angle. Seeing the reflection directly under the light source is impossible, unless you are the light source.

  • What does this have to do with painting? Well, here comes rule number two. The position of the observer influences the shading. The light source can be fixed, the object may be fixed, but every observer will see it a bit differently. It's obvious when we think about perspective, but we rarely think of lighting this way. In all honesty do you ever think about the observer when setting the lighting?

    As a curiosity: have you ever wondered why we tend to paint a white grid on a glossy object? Now you should be able to answer this question yourself. Also, now you know how glitter works!

  • Value Is the Amount of Seeing