Note! I recommend reading this BEFORE watching the timelapse video!The way we light our image will greatly define the “Look and feel” of the final work, as such, choosing an adequate lighting can greatly help us convey what we wish to our audience.
Take as example the above image. We have the exact same sphere on a flat surface, and yet just changing the position of our light source can greatly change the message we give. Lighting can make an image more dramatic or more serene, give a character more impact, or help us merge him with the environment.
As I mentioned in the original pol post, lighting is a HUGE theme, and will require multiple lessons/tutorials to give you all even just the basics of each of its components. As such, on this tutorial I will focus on just the “Main Light” and how it works on diffuse surfaces (reflective, transparent, textured and other materials will require a lesson of their own XD). We will also only work on grayscale for now, as the color of the light, local color and the colors surrounding the object will also be left to further lessons.
Ok, to start we need to understand how lighting affects objects (how to paint light on a surface) and the different kinds of light sources:
The Form Principle
An easy way to determine how to draw the light on an object is to think of the light as individual “rays” and divide the object into basic shapes, the determining how those rays fall on the object. The way the faces of the object face the light source will determine how much “lighting” they’ll get, Sam Nielson explained it really well with a diagram like the one we see at the top of the image; we have 2 surfaces with the same length, one facing the light source head on, while the other is at a slight angle. We can see how the one parallel to the light source gets more “rays” of light than the one in an angle.
Using this we can determine how intense to make the lighting on the different surfaces of our object. We can also determine something called the “Terminator” which basically is the point where the object stops receiving light directly from our main light source, as none of its “faces” receive any light rays. This can be very easily seen with the Moon, since its only lit by one main light source: the Sun. Hence we can clearly see the terminator on each of its phases, similar to the above diagram.
Lastly, it's very important to know how to manage the lighting fall-off on the object's surface. This will greatly help us convey the shape of the object to our viewer, as round areas often have a smooth gradient-like fall-off, while hard edges have a sharp contrast. We can see this on the way a cube is shaded very differently from a sphere.
This takes a ton of practice, and I really suggest starting with basic geometric shapes (sphere, cone, cylinder, cube, pyramid), since most objects we paint can be deconstructed into these simple shapes to get a good idea of how to light them.
Light Sources
Knowing this we can start determining the kind of light source that would best work for our scene! There are maaaany types of light sources, but here are 3 of the main ones:
Directional: With this kind of light source, all the light rays follow the same direction and are parallel to each other. This causes all the shadows on our scene to “fall” on the same direction and angle, likewise, any object on our scene will receive the light with the same intensity no matter where it is in the scene (unless it's covered by other objects of course). This light source is mostly used for paintings depicting outdoors scenes during the day. Example: the Sun.
Point: Here all the light rays come from the same point in space and expand outwards in all directions. Generally the light intensity produced by this kind of source has a fall-off depending on the distance, so objects closer to the light source will receive light with more intensity than those further away (as seen in the image above). Also, since the light rays aren’t parallel to each other, the shadows and the terminators of each object will be affected depending on their position relative to the light source. Examples: light bulb, candle, torch, flare, etc...
Diffuse: This kind of lighting usually is produced by a surface or object, rather than a single point of light, and the resulting light rays are projected in multiple angles from this shape. This causes the light/shadow contrast to be extremely low, the edges of the shading losing their sharpness, causing all the objects to have shadows without clear edges (as shown on the image above). Examples: overcast sky, some studio lights, large screens, etc
Methodology (explanation of what you see in the time-lapse video ^^)
Ok, now onto the actual methodology I follow when shading an object. I usually start by making a few quick “lighting maps” bellow my sketch, these should only take about a minute or so each, only detailed enough to give us an idea of how the object would look under that particular light source/direction (you can also see me making these at the beginning of the time-lapse video).
I then select the one I think works best, keeping that image I did close as a map to follow when doing the actual shading. I usually start with a neutral gray at 50% luminosity, so i can both lighten and darken my image. I start with a fairly large brush, defining the big shapes similarly to what I did with the quick light map, making sure to not zoom in, as its best to have the big picture in mind on this first stage.
Once that’s done, I start using smaller and smaller brushes, helping me define the details shown in the sketch (so far all these is painted underneath the sketch layer, to keep it as a guide). I sometimes turn the sketch layer on and off to see how well the shapes are understood without the help of the lines, once the image doesn’t need the sketch that much, I go on to the next stage.
To finish up, I start painting on a new layer on top of the sketch, here I can add as much detail as I want, helping the image work without the lineart and also to create new details that didn’t appear on the lines, such as textures and individual hair/fur, etc…
These stage can be taken as far as you want, and is usually the most time consuming part of my digital paintings. This is of course not needed if you intend to keep the lineart though! So keep in mind what you wish to accomplish.
Finally, I recommend you practice with different shading styles, you can try cell shading, using the terminator as a guide to create sharp shadows, shading with textures, cross hatching, etc… you can do a lot of stuff so try out multiple ones to see which you like best!
Another nice way to practice shading is painting from life, sketching objects you have in front of you and lighting them from multiple angles ^^ And as always, if you guys have any questions I’ll be happy to answer! I hope this quick tutorial helped you!
-Tiesci