the term value contrast refers to the relationship between areas of dark and even darker.

CMYK is a subtractive model wherein the four inks remove specific wavelengths of light, reflecting only the narrow range each is associated with.

In color printing, your printer likely has cyan, magenta, yellow, and black (CMYK) ink cartridges. When working with color, it's important to know which 'color space' you are working in, as different color spaces map to different measurement systems. For this document, we'll use terminology as it is defined in the W3C, in the CSS Color Module Level 4 For example, the color 'crimson red' may be described in hex values as #990000 by some and #DC143C by others. The 'L' in the HSL color space is sometimes referred to as 'luminosity,' and other times as 'lightness.' Even something seemingly simple, like naming common colors, can be open to debate.

In others, 'chroma' and 'saturation' are two different concepts. For example, 'saturation' is known as 'chroma' in some circles. 'Luminance' and 'Saturation' are particularly important to get right. Terminology can be confusing because different terms often describe the same thing. Additionally, the above media queries enable developers to provide alternative user experiences when user preferences indicate preferred contrast levels, automatically adjusting levels depending on the user's location and what kind of screen they are using. When supported, the Ambient Light Sensor interface returns the current light level or illuminance of the ambient light around the hosting device, enabling a web page to be aware of any change in the light intensity, and consequently, adjust the text accordingly.

Fortunately, there are media queries that enable developers to provide styles based on user preferences, including contrast and color scheme preferences. How the viewer perceives color after it gets to their eyes is yet another matter, and can be affected by overall health. Font size, font style (some fonts are so thin or fancy that they present accessibility problems on their own), background color, the size of the background space around the text, even pixel densities, and more all affect how color is delivered from the screen.Ī viewer's distance from the screen, the ambient background, the health of his eyes, and more all affect how that color is received by the viewer. Regarding accessibility, using certain color combinations has more impact than others. Perception of color in a well-lit room will be different than perception of that same color on that same computer screen in a dark room.

The term value contrast refers to the relationship between areas of dark and even darker.