Complete Guide to White Balance Adjustment - Precisely Controlling Color Temperature and Tint
White Balance Principles - What Color Temperature Means
White balance (WB) is a color correction process that reproduces white objects as white regardless of light source color. Human eyes achieve this through "chromatic adaptation," but camera sensors record light wavelength distributions directly, causing light source color to affect the entire image.
Color Temperature: A numerical value in Kelvin (K) representing light source color. Based on black body radiation theory, it's defined by the correspondence between heated object temperature and emitted light color. Low temperatures (2000-3000K) indicate warm reddish light; high temperatures (7000-10000K) indicate cool bluish light.
Typical light source color temperatures:
- Candle: ~1800K (strong warm)
- Incandescent bulb: ~2700K (warm)
- Sunrise/sunset: ~3000-3500K
- Fluorescent (daylight): ~5000K
- Noon sunlight: ~5500K (daylight reference)
- Overcast: ~6500-7500K (slightly cool)
- Shade: ~7000-8000K (cool)
- Blue sky (north-facing): ~9000-12000K (strong cool)
What camera WB settings mean: Setting "5500K" tells the camera to "assume the light source is 5500K and compensate accordingly." If the actual source is 5500K, color reproduction is accurate. But setting 5500K under 3000K incandescent lighting produces insufficient compensation, resulting in an orange-tinted image.
Shooting WB Strategy - Presets vs. Manual Settings
White balance settings during capture directly affect final quality for JPEG shooting and processing efficiency for RAW shooting. Here's the optimal strategy for different situations.
Auto WB (AWB) characteristics and limitations: Modern camera AWB is excellent, achieving accurate color in most situations. However, misjudgment occurs when: (1) A single color dominates the frame (green forest, blue ocean). (2) Intentionally colored lighting exists (stage lights, neon). (3) Mixed light sources are present (window daylight + indoor fluorescent). AWB targets "neutral color reproduction," potentially neutralizing intentional sunset warmth or blue-hour coolness.
Preset WB usage: Camera presets (Daylight, Cloudy, Shade, Fluorescent, Tungsten) apply fixed color temperature values. Daylight = 5200K, Cloudy = 6000K, Shade = 7000K are typical. When the light source is clear, presets provide more consistent results than AWB.
Manual WB (Custom WB): Photograph a gray card or white paper to set a reference. Used for product photography and studio work requiring accurate color. X-Rite ColorChecker enables calibrating not just WB but the entire color profile.
Direct Kelvin value input: Advanced setting for directly entering color temperature numerically. To emphasize sunset warmth, set higher than actual temperature (7000-8000K); for cool impressions, set lower (4000-4500K). With RAW shooting, this can be freely changed later, so AWB during capture is perfectly acceptable.
RAW Processing White Balance - Lightroom Practical Techniques
RAW files record white balance in an undetermined state, allowing degradation-free adjustment during processing. Here are precise WB adjustment techniques in Lightroom.
Temperature and Tint sliders: Lightroom's Basic panel has two WB sliders. "Temp" adjusts the blue-yellow axis, directly controlling Kelvin values. "Tint" adjusts the green-magenta axis, used for correcting green casts common under fluorescent lighting.
Eyedropper tool (WB Selector): Click a neutral (white or gray) area in the image to automatically correct RGB values to equal. The ideal target is light gray (RGB around 200) rather than pure white, which may be clipped and unreliable as a reference.
Handling mixed light sources: When natural window light (5500K) mixes with indoor fluorescent (4000K), no single WB setting corrects everything. Solutions: (1) Set WB to the primary light source and handle secondary source influence with local adjustments. (2) Use Lightroom's Adjustment Brush for per-region temperature control. (3) Unify light sources during shooting (turn off fluorescents, close curtains).
Creative WB applications: WB serves not only "accurate reproduction" but intentional color mood. Higher temperature (7000K+) creates warmth; lower (4000K-) creates cool, urban impressions. Film color grading commonly shifts WB intentionally to match scene emotions.
The Science of Color Temperature - Black Body Radiation and CIE Chromaticity
Understanding the physics and color science behind white balance enables more accurate and intentional color control. Comprehend color temperature on the CIE chromaticity diagram and the relationship between Correlated Color Temperature (CCT) and deviation (Duv).
Black body radiation and Planck's law: An ideal black body (perfect radiator) emits light with wavelength distribution dependent on temperature. Low temperatures produce red light (long wavelength dominant); high temperatures produce blue light (short wavelength dominant). This temperature-color correspondence defines "color temperature." Sunlight (~5778K) has a near-continuous spectrum similar to black body radiation.
Planckian locus on CIE chromaticity diagram: Plotting black body color temperatures on the CIE 1931 xy chromaticity diagram traces a curve (Planckian locus) from 1000K to infinity. Real light sources don't always fall exactly on this locus - deviation from it is perceived as "color cast." Fluorescents deviate toward green; LEDs deviate in various directions.
CCT and Duv: For light sources not on the Planckian locus, color temperature is approximated as "Correlated Color Temperature" - the temperature of the nearest point on the locus. Duv represents distance from the locus: positive values indicate green deviation, negative values indicate magenta deviation. Lightroom's Tint slider adjusts this Duv value.
Color Rendering Index (CRI): Even with identical color temperatures, different spectral distributions produce different object appearances. CRI evaluates how accurately a light source renders object colors on a 0-100 scale. Sunlight is CRI 100, quality LEDs are CRI 95+, cheap fluorescents are CRI 70-80. Under low-CRI sources, even accurate WB settings produce inaccurate reproduction of certain colors.
Programmatic WB Correction - Auto White Balance Algorithms
Understanding camera and software auto white balance (AWB) algorithm principles and implementing them in Python provides practical knowledge for building custom image processing pipelines with WB correction.
Gray World hypothesis: The simplest AWB algorithm, assuming "the average color of the entire image should be gray (neutral)." Calculate mean R, G, B channel values and adjust gains to equalize them.
avg_r, avg_g, avg_b = img[:,:,2].mean(), img[:,:,1].mean(), img[:,:,0].mean()
avg = (avg_r + avg_g + avg_b) / 3
img[:,:,2] = np.clip(img[:,:,2] * (avg / avg_r), 0, 255)
Simple but fails when a single color dominates the frame (blue sky, green forest).
White Patch hypothesis: Assumes "the brightest point in the image is white." Detects maximum values per channel and scales to 255. Effective when specular highlights or reflections exist, but fails without white objects in the scene.
Temperature to gain conversion: Algorithms converting specified Kelvin values to RGB gains are implementable. Tanner Helland's algorithm is widely used, providing approximation formulas converting color temperature to RGB values across 1000K-40000K range.
Machine learning AWB: Modern smartphone cameras use CNN-based AWB. Trained on large datasets of images paired with correct WB values, they achieve high-accuracy WB estimation including scene recognition (indoor/outdoor, natural/artificial light). Google's research reports accuracy far exceeding traditional statistical methods.
Practical WB Troubleshooting - Common Problems and Solutions
Real-world white balance problems and their specific solutions for immediate application during shooting and processing work.
Problem 1: Green cast under fluorescent lighting
Fluorescent lamps produce mercury emission line spectra, creating different color reproduction than continuous-spectrum sources. Green casts are pronounced with older tubes. Solution: Adjust Lightroom's Tint slider toward magenta (+10 to +20). Reducing green saturation individually in the HSL panel also works.
Problem 2: Mixed light sources (window + indoor)
Different color temperature sources create region-specific color casts. Solution: (1) Set WB to primary source. (2) Use Adjustment Brush for per-region temperature correction. (3) Unify sources during shooting when possible.
Problem 3: LED color rendering issues
Cheap LEDs have spectral gaps, causing unnatural skin tones and red objects even with correct WB. Solution: Fine-tune individual hue/saturation/luminance in HSL panel. Fundamental fix requires high-CRI (95+) LED lighting.
Problem 4: Inconsistent WB across continuous shooting
AWB during burst shooting varies WB per frame as composition changes, producing inconsistent color. Solution: (1) Use manual WB or presets during shooting. (2) Set WB on one reference image in Lightroom and "Sync Settings" across all images. (3) Always lock WB for video.
Problem 5: RAW vs. JPEG WB differences
Camera LCD preview color (JPEG) may differ from RAW processing results because camera JPEG engines and processing software handle color differently. Solution: Select "Camera Standard" in Lightroom's Camera Profile to approximate in-camera JPEG color reproduction.