APCA Perceptual Contrast & Ambient Lux Analyzer

Evaluate text legibility, WCAG 3.0 APCA Lc scores, and ambient room light contrast derating across OLED and LCD displays.

W3C APCA 0.98G & WCAG 2.1 ERGONOMICS EVALUATOR

APCA Perceptual & Ambient Contrast Inspector

PREFERRED READABILITY (Lc ≥ 75)

🎨 COLOR, FONT & AMBIENT CONTROLS

Text Color

Background

Quick Presets

Font Weight

Font Size

Panel Technology

Screen Reflectance

Ambient Room Illuminance:300 Lux (Office)

10 Lux (Dark Room)300 Lux (Office)2000 Lux (Direct Sun)

Display Peak Luminance:350 Nits

80 Nits (Dim)350 Nits (Standard)1000 Nits (HDR Peak)

📊 CONTRAST & ERGONOMICS RESULTSASTIGMATISM RISK: LOW

APCA Lightness Contrast

Lc -82.4

Light on Dark

WCAG 2.1 Ratio

14.85:1

AAA Pass (Normal)

Ambient Contrast (ACR)

145.2:1

92.7% Glare Loss

Live Typography Preview Canvas

Perceptual Display Contrast Calibration

The quick brown fox jumps over the lazy dog. APCA 0.98G evaluates lightness contrast ($L_c$) based on human spatial frequency sensitivity, font weight, and ambient display glare.

📏 APCA Font Size Recommendation:Min 14px @ Weight 400

WCAG 2.1 Conformance

Normal Text AA:PASS

Normal Text AAA:PASS

Ambient Glare & Reflectance

Perceived Black:2.39 Nits

Glare Severity:MODERATE

Ergonomic & Optometric Advice:

Text contrast and display ambient contrast are well within ergonomic recommendations.

Browser & OS Color Management Limitations

Software-based visual evaluation patterns are subject to Web browser color space mapping (sRGB / Display P3), operating system display scaling, ICC profile overrides, and GPU driver settings. While Monitor Test Hub utilizes hardware-accelerated WebGL 2.0 rendering pipelines, browser-based tests cannot fully replace physical hardware colorimeters or spectrophotometers (e.g., Calbrite Display Plus HL, X-Rite i1Display Pro) for color-critical prepress workflows.

OPTOMETRIC ERGONOMICS & NON-MEDICAL NOTICE

Monitor Test Hub is an engineering calibration utility for electronic visual displays (LCD, OLED, QD-OLED, MicroLED) and mobile touch digitizers. This software is NOT a medical eye exam, optometric vision test, or diagnostic health utility.

To reduce Digital Eye Strain (DES) during display calibration, apply optometric ergonomics:

The 20-20-20 Rule: Every 20 minutes, look at an object at least 20 feet away for 20 seconds.
Ambient Illumination: Ensure room ambient lighting matches display brightness levels (~100–150 nits for standard SDR workloads).
Optimal Viewing Distance: Place your screen approximately 20 to 30 inches (50–75 cm) from your eyes.

Frequently Asked Questions

What is APCA contrast and how does it differ from WCAG 2.1?

APCA (Advanced Perceptual Contrast Algorithm) is the proposed contrast standard for WCAG 3.0. Unlike WCAG 2.1 which uses a simple 4.5:1 ratio, APCA calculates non-linear human visual perception based on spatial frequency, font weight, background polarity, and ambient room light.

What is an acceptable APCA Lc value for web & UI text?

An APCA Lc score of 75+ is recommended for primary body text, Lc 60+ for secondary text, and Lc 45+ for large headings (24px+). Scores below Lc 45 fail accessibility legibility guidelines.

How does ambient room lighting (Lux) affect display contrast?

Ambient room light reflects off screen surfaces, raising effective black levels (especially on glossy OLED or IPS panels). Our calculator applies ISO 9241-307 specular reflection formulas to derate contrast ratio based on room lux.