When multiple elements of an image are the same color or light level – for example, a blue boat on blue waters – the difference in contrast is what makes it possible to distinguish one detail from another. The human eye can often make these adjustments automatically, but people with vision difficulty, low vision, or color blindness often need color contrast to be manually adjusted to maximize viewability of the details (or text) within an image.
The concept of color contrast is biological in nature but has become understood in the common vocabulary through technological solutions that are meant to mimic the natural contrasting function of the human eye. These solutions make it more possible for someone with vision difficulties such as cataracts, macular degeneration, or a person who is is color blind to see the details of an image.
Modern color contrasting is based on three formulae:
1. The Weber Contrast: Highlighting small features on a large, consistent background.
2. The Michelson Contrast: Highlighting both light and dark features of equal prominence in an image.
3. The RMS Contrast: Adjusting the intensity of all colors in an image.
With the advent of consumer technologies, color contrast is more common than ever. Both Apple and Microsoft, for example, include a “heightened contrast” mode standard on their computers. Apple and Google also have developer guidelines to help new app developers build with contrast in mind.
It’s also worth noting that color contrast is modified not just for people with vision difficulties, but for overall viewability and quality of an image. A common example in photography is increasing the color saturation of an image to make it stand out. In social media, an example of color contrast is adding highlights behind text that is overlaid on an image to ensure the text is easy to read. These kinds of adjustments are helpful for people with vision difficulties but are also good business practice for making images and text easy to understand.