Value

Studying Light and Dark

We've been talking a lot about illusions in this course, and guess what? This lesson is about illusions as well. In this lesson, we'll talk specifically about how our eyes can play tricks on us with regard to light and dark.

In the field of design, we refer to light and dark as value. Since in image's color can be broken down into different parts - as we'll see in much more detail next chapter - we need to use much more specific terms for those parts.

A Preview into Color Theory

Just to give you a preview of next week's lesson on color, in the HSV system color can be described in terms of its hue (where it is on the rainbow), saturation (how vibrant or rich the color is) and value (how light or dark the color is.

There are other systems like RBG, CMYK, and LAB, which break down colors in different ways. We'll learn all about those systems and about color theory next week.

It just so happens however that our eyes' recepters are actually split into two types - rods and cones. The rods are responsible for detecting light and dark while the cones detect color. So, in this lesson, we'll be focusing just on the rods.

Optical Illusions with Value

You may not realize it, but our brains are constantly compensating for what we are seeing in order to create the most optimal image for us. Optical illusions occur when and image exploits our brain's attempt to alter images for us and causes it to think it is seeing something it's not.

Vsauce - Moving Illusions

I will show several examples of illusions of value, but first, let's watch this fascinating video that explains in more detail what illusions really are.

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Which square is lighter?

As you can see in the following image, it may appear to you that the B square is actually lighter, but as we bridge the gap between A and B, we will see that they are actually the same value.

This is because our brains use context to help determine what it believes is light or dark.

Illusion of Gradient

In this first example, you will see a rectangle in the center that appears to have a gradient, meaning it looks like it gets darker as it moves to the right. However, once the gradient background is removed, you will see that it is just a plain grey square.

This is another example of our brains compensating based on context.

Halftone

Halftone is a process of converting an image with a wide variety of values or different shades of grey into purely black or white. This process is necessary for the printing process since printers are often dealing with one color of ink at a time (in this case, black) and need to give the illusion that there are actual shades of grey.

Fellow is another gradient that has been converted into halftone. As you can see, there is a grid of circles that get smaller as they move to the right.

If you squint your eyes, the dots will blur and you will see a seamless gradient.

Let's Practice!

Now that we've gone over general theory, let's practice shading on our own.

Pencil Technique

This video has some great advice on general techniques for holding the pencil. Please watch this video and practice some of the examples on your own.

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Questions?

As always, please email me if you have any questions! jearley1@ivytech.edu