Visual acuity Human vision adapts over a wide range of intensities. Your viewer's impression of your work will be determined by her viewing conditions, so you must take into account the expected viewing conditions when you create your work. Visual acuity is at a maximum only in a small portion of the visual field. As the angle from the center of the gaze increases, acuity is reduced, but sensitivity to movement and flicker increases. To make effective use of vision in an interactive system, you must be familiar with these characteristics.
Contrast sensitivity is the measure of visual acuity.
Familiarity with contrast sensitivity will help you to determine how much detail you can expect your viewer to perceive. We will define contrast ratio, and explain how you can maximize contrast ratio to improve subjective sharpness. We will explain how this limit relates viewing distance to the amount of detail that your user can be expected to perceive. We will explain how the colors that can be reproduced by a particular device are restricted by the gamut of the device, and outline strategies that are used to map colors from one gamut to another. An image, or a user interface, must live within a palette that is related to this small set of colors.