White Balance

Understanding White Balance

White balance is a fundamental calibration parameter that ensures LED displays reproduce neutral grays correctly. Improper white balance causes whites to appear tinted—typically pink/warm or blue/cool—degrading overall image quality.

White Balance Basics

**RGB Ratio:** White balance adjusts the relative intensity of red, green, and blue LEDs to achieve neutral white at a specified color temperature.

**Gray Scale:** Proper white balance means neutrality is maintained from black through all gray levels to full white.

Color Temperature

**Common Targets:**

• 6500K (D65): Video standard, cool white
• 5600K: Daylight/film standard
• 5000K (D50): Print viewing standard
• 3200K: Tungsten/warm match

**Choosing Temperature:** Match the intended viewing environment and content source specifications.

White Balance Adjustment

**Processor Controls:**

• RGB gain (affects high end)
• RGB offset/bias (affects low end)
• Gamma curves (affects mid-tones)

**Calibration Process:** 1. Set target color temperature 2. Display white at 100% 3. Measure with colorimeter 4. Adjust RGB gains to match target 5. Verify at lower brightness levels 6. Adjust gamma/offset if needed

Gray Scale Tracking

**The Challenge:** White balance at 100% may not hold at lower brightness. LEDs can shift color as they dim.

**Verification:** Check white balance at multiple levels:

• 100%, 75%, 50%, 25%, 10%
• Adjust if significant drift

**Solutions:**

• Multi-point gamma adjustment
• Per-level RGB correction
• Higher-quality LED selection

Common Issues

**Pink/Warm Tint:** Too much red relative to green and blue.

**Blue/Cool Tint:** Too much blue relative to red.

**Green Tint:** Often indicates mismatched panel batches.

**Inconsistent Across Panel:** Needs pixel-level calibration, not just overall white balance.

Verification Methods

**Visual:** Display gray scale pattern, check for neutral appearance.

**Colorimeter:** Measure x,y coordinates or CCT (correlated color temperature).

**Camera:** Set camera to known white balance, check appearance on monitor.

Environmental Factors

**Warm-Up Time:** Allow 30+ minutes before final white balance verification.

**Temperature:** Ambient temperature affects LED color output.

**Aging:** LEDs shift color over lifetime; recalibration needed.

Documentation

Record:

• Target color temperature
• Date of white balance
• Verification measurements
• Equipment used