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Legibility

Updated

What it does

This KPI measures the ease of reading text in marketing assets, focusing on the color contrast between the text (font) and its background, as well as the size of the text. This metric quantifies readability by analyzing each block of text detected in an asset, taking into account color contrast and font size. The overall score reflects how readable the text is across the entire asset.

 

In this example we have five texts. The mean across the five scores - the total score - is 50. This is indicating low legibility overall (red color). 

 

Why it matters

Legibility is critical to effective marketing communications. It ensures that the message is clearly conveyed and easily understood. High legibility facilitates information retrieval and enhances the user experience. It's especially important for inclusivity, catering to those with visual impairments. In addition, clear and legible text reflects professionalism and legitimacy, which are essential for building trust in a brand.

 

How it works

Text on an asset is recognized using a text recognition model that groups recognized words into blocks for enhanced color contrast analysis between the text and its background. A dedicated algorithm measures the luminance contrast between the most prominent text and background colors and adjusts the legibility score based on text size, as larger text generally improves readability. The overall legibility score for the asset is calculated as an average across all blocks of text, with each block's score influenced by both color contrast and font size.

 

How to achieve great results

  • Ensure high color contrast between text and background to make the text stand out

  • Avoid cluttered/structured (e.g. gradients) backgrounds for important texts

  • Choose larger text sizes to improve readability, especially for critical information such as key messages, brand names, and calls to action.

AI models used

The process uses

  1. a world-class OCR model capable of recognizing a wide range of fonts and styles in diverse visual environments
  2. an algorithm to evaluate color contrast of text against background
  3. an algorithm to measure the font size

This approach leverages knowledge of how the human brain perceives and processes color contrast, ensuring that the assessment of text legibility closely matches the human visual experience.

 

Science Background

The following chart is intended to demonstrate the spatially dependent nature of human contrast sensitivity, which is why Brainsuite's Legibility KPI incorporates text size.

This is a chart of the human contrast sensitivity curve. A blue line curves down to the right where the Y axis is contrast sensitivity, and the X access is spatial frequency, increasing toward the right. An increase in spatial frequency means elements are smaller and thinner. On the right of this info graphic are samples of text from very large and bold to very thin and small, with red lead lines indicating approximately where those samples fall on the contrast sensitivity curve. All of the text samples are at the exact same CSS color of #c7c7c7, the top very large and bold headline is legible but as the fonts become thinner and smaller they literally fade out as if becoming lighter gray, even though they are all at the exact same color.

(c) Myndex Research

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