Without light, we would see nothing. When we look at something, there’ll always be some light that is acting on it, and the kind of lightning heavily influences the look, mood, and interpretation of a design. Because we’re so used to always having one or multiple sources of light, a design is aesthetically pleasing when it doesn’t contradict the rules of light, but instead uses them to establish hierarchy and order. On top of that, light automatically creates the illusion of depth, and helps with one of the most important principles of design: contrast.
Types of Light
As you start with your design piece, you’ll need to establish the light source(s) working on it. Arbitrarily applying lighting to every element is never a good idea, as it would create inconsistencies and confuse your audience about the setting and environment of the design. Every light source has a few properties you need to figure out: position, strength and colour.
The position is the placement in the three-dimensional world. The light can be above all elements, in between them, behind, in front – whatever you want. Objects with top-down lighting look natural and friendly, while objects with bottom-up lighting look unnatural and scary. In general, it’s also preferred to have a light source shining from an angle, instead of straight down at objects.
The strength is the amount in which the light influences its surroundings. A weak light (such as a light bulb) only affects the elements nearest to it, and only adds a little bit of contrast. A strong light (such as the sun) affects all elements in the exact same way, and is very apparent. A weak light creates shadows and highlights with very soft edges, while a strong light creates hard edges.
The colour of the light is, obviously, what colour light waves the light emits. The sun shines with yellow/white light, which is good, as it shows every object in its true colours. But, for example, a blue light sets a much grimmer or darker mood, while a red light creates the sensation of warmth and sunset.
Visual Cues for Light
How then, do we create these illusions of light in our designs? Well, just as with the illusion of three-dimensional form, there are certain visual cues we can employ.
Light shows itself through highlights (where light hits the object directly) and shadows (places the light can’t reach). No matter what colour an object is, its highlights will have a higher brightness, and its shadows a lower brightness than usual. We call the amount an element is in the light or shades its value.
The most apparent shadow of any object is its cast shadow, which is a shadow cast on surrounding elements. Technically, this means that it isn’t part of the element anymore, as the actual value difference happens on the other affected elements. I think it’s important to realize this property of light, as it binds elements together and can create unexpected shapes.
The highlight on objects is often smaller and less obvious, but it still excites strong feelings of power, brilliance, fluorescence, and amplitude.
The general rule is that elements of higher value draw attention or add emphasis. By adding a smooth transition between the light and dark parts of an element (a gradient), we invite the viewer’s eye to then follow that path, helping us direct the viewer around the design.
The other important visual cue is transparency, sometimes called opacity or alpha. When an element is transparent, we can see through it (to some degree). When an element is opaque, which most elements in the real world are, we can’t see through it at all.
The important thing to notice is that an element can only be transparent if there’s light acting on it! When a transparent object overlays another object, the light waves that return to our eyes are a mix of the colours and textures of both objects. Therefore, more transparency creates a stronger sense of lighting.
You must be careful, however, not to overdo it. Most objects in the real world aren’t transparent (I mean, can you name anything transparent besides glass?), and ignoring that fact in your designs could turn it into a big, artificial mess.
Nevertheless, transparency is a good method for adding multiple layers of complexity to a design, and overlapping shapes while still being able to see both of them. It’s effective in creating depth, without sacrificing visual data.
On the other hand, this means that transparency is rarely suited for the purpose of clarity, but instead used to create dense, layered imagery. Transparency connects the two (or more) objects that mix, and automatically combine or contrast them. Our brain simultaneously perceives both objects at different spatial locations – sometimes one seems in front of the other, sometimes it’s the other way around. This adds to the visual intrigue of a design, but is a bad idea for efficient or simple designs.