Formula for color contrast between text and background

1. How is Colour contrast calculated?
2. What is a 4 5 1 contrast ratio?
3. How do I find the contrast ratio of a color image?
4. Is there enough contrast between background colors and font colors?

How is Colour contrast calculated?

Contrast is calculated using "relative luminance", which is defined as: The relative brightness of any point in a colorspace, normalized to 0 for darkest black and 1 for lightest white. The relative luminance can be calculated from any colour code (like HEX or RGB).

What is a 4 5 1 contrast ratio?

The 4.5:1 ratio is used in this provision to account for the loss in contrast that results from moderately low visual acuity, congenital or acquired color deficiencies, or the loss of contrast sensitivity that typically accompanies aging.

How do I find the contrast ratio of a color image?

Procedure. L = 0.2126 * R + 0.7152 * G + 0.0722 * B where R, G and B are defined as: if R sRGB <= 0.04045 then R = R sRGB /12.92 else R = ((R sRGB +0.055)/1.055) ^ 2.4. if G sRGB <= 0.04045 then G = G sRGB /12.92 else G = ((G sRGB +0.055)/1.055) ^ 2.4.

Is there enough contrast between background colors and font colors?

To make your content accessible, you should have high contrast between all text and its background color. If your text is dark, your background should be light, and vice versa. Black text on a white background is recommended for paragraphs of text.