Luminance & Brightness Comparator

Analyze and compare color luminance and brightness values to create accessible and visually balanced designs. Understand how different colors are perceived and ensure sufficient contrast for readability.

Relative Luminance:0.000
Perceived Brightness:0.000
Relative Luminance:1.000
Perceived Brightness:1.000

Comparison Results

Contrast Ratio:21.00:1
WCAG Level:AAA
Luminance Difference:1.000

Generated CSS

/* Color values */
--color-1: #000000;
--color-2: #FFFFFF;

/* RGB values */
--color-1-rgb: 0, 0, 0;
--color-2-rgb: 255, 255, 255;

/* Relative luminance */
--color-1-luminance: 0.000;
--color-2-luminance: 1.000;

/* Contrast ratio: 21.00:1 */

Understanding Luminance and Brightness

Luminance and brightness are crucial concepts in color theory and accessibility. While often used interchangeably, they represent different aspects of how we perceive light and color.

Relative Luminance

Relative luminance represents the objective measurement of light intensity as perceived by human vision. It's calculated using specific coefficients for RGB channels:

L = 0.2126 * R + 0.7152 * G + 0.0722 * B

Where R, G, B are normalized to [0,1]

Perceived Brightness

Perceived brightness is a subjective measure of how the human eye interprets light intensity. It's influenced by:

  • Surrounding colors and contrast
  • Viewing conditions
  • Individual perception differences
  • Cultural and psychological factors

Calculating Color Values

1. RGB to Relative Luminance

The process of converting RGB colors to relative luminance involves several steps:

// Step 1: Normalize RGB values to [0,1]
let r = R / 255
let g = G / 255
let b = B / 255

// Step 2: Apply gamma correction
if (r <= 0.03928) r = r / 12.92
else r = Math.pow((r + 0.055) / 1.055, 2.4)

if (g <= 0.03928) g = g / 12.92
else g = Math.pow((g + 0.055) / 1.055, 2.4)

if (b <= 0.03928) b = b / 12.92
else b = Math.pow((b + 0.055) / 1.055, 2.4)

// Step 3: Calculate luminance
let L = 0.2126 * r + 0.7152 * g + 0.0722 * b

2. Contrast Ratio

The contrast ratio between two colors is calculated using their relative luminance values:

// L1 = luminance of lighter color
// L2 = luminance of darker color
ContrastRatio = (L1 + 0.05) / (L2 + 0.05)

3. Perceived Brightness

A common formula for perceived brightness (also known as luma) is:

// Using Rec. 601 coefficients
Brightness = (0.299 * R + 0.587 * G + 0.114 * B)

Applications in Design

Accessibility Compliance

WCAG 2.1 guidelines specify minimum contrast ratios:

  • Normal Text: 4.5:1 minimum
  • Large Text: 3:1 minimum
  • UI Components and Graphics: 3:1 minimum

Visual Hierarchy

Use luminance differences to create effective visual hierarchy:

  • Higher contrast for primary content
  • Medium contrast for secondary information
  • Lower contrast for decorative elements
  • Strategic use of brightness for emphasis

Color Schemes

Consider luminance when creating color schemes:

/* Example of a balanced color scheme */
:root {
  --text-primary: #1a1a1a;    /* High luminance contrast */
  --text-secondary: #666666;  /* Medium luminance contrast */
  --text-tertiary: #999999;   /* Lower luminance contrast */
  
  --background: #ffffff;      /* Base luminance */
  --surface: #f5f5f5;        /* Slight luminance difference */
}

Related Tools and Resources

Frequently Asked Questions

What's the difference between luminance and brightness?

While related, luminance and brightness serve different purposes:

  • Luminance: Objective measure of light intensity, used for technical calculations and accessibility standards
  • Brightness: Subjective perception of light intensity, influenced by surrounding context and human perception

How do I ensure my design meets WCAG contrast requirements?

Follow these steps:

  1. Calculate the relative luminance of both colors
  2. Determine the contrast ratio using the formula
  3. Compare against WCAG requirements:
    • 4.5:1 for normal text
    • 3:1 for large text and UI components
  4. Adjust colors if needed to meet requirements

How can I use luminance to improve visual hierarchy?

Consider these guidelines:

/* Example luminance ratios for hierarchy */
.primary-content {
  /* High contrast - easy to read */
  color: #000000; /* L ≈ 0 */
  background: #ffffff; /* L ≈ 1 */
}

.secondary-content {
  /* Medium contrast - still readable */
  color: #666666; /* L ≈ 0.3 */
  background: #ffffff; /* L ≈ 1 */
}

.tertiary-content {
  /* Lower contrast - de-emphasized */
  color: #999999; /* L ≈ 0.6 */
  background: #ffffff; /* L ≈ 1 */
}

Should I always aim for maximum contrast?

Not necessarily. Consider these factors:

  • Content importance and hierarchy
  • User context and environment
  • Design aesthetic and brand guidelines
  • Eye strain and readability for long-form content

Best Practices for Color Perception

Testing Environment

  • Test colors under different lighting conditions
  • Consider device calibration differences
  • Account for ambient light variations
  • Test across different screen types

Design Implementation

  • Use relative units for better adaptability
  • Consider color context and interactions
  • Plan for both light and dark modes
  • Document color decisions and rationale