RGB to Lab Converter
Free, accurate, and instant conversion. Preview your color in real-time on digital and print mockups.
Source Input RGB
/* CSS Variable */ --color-primary: #000000; /* Standard */ color: #000000; background-color: #000000;
Perceptual Perfection: RGB to Lab
RGB is messy. A change of "10" in Blue is visible. A change of "10" in Bright Green is practically invisible. This makes it terrible for color matching.
CIELAB (L*a*b*) fixes this. It is Perceptually Uniform. If two colors are distance "5" apart in Lab space, they will look exactly "5 units" different to the human eye, no matter if they are red, blue, or grey.
L* (Lightness)
0 to 100.
Separates brightness completely from color info.
a* (Green-Red)
Negative is Green.
Positive is Magenta/Red.
b* (Blue-Yellow)
Negative is Blue.
Positive is Yellow.
Opponent Color Theory
Lab is based on how our brain processes signals. We cannot see "Greenish-Red" or "Yellowish-Blue". These are opponent colors.
- The a* axis represents the battle between Green and Red.
- The b* axis represents the battle between Blue and Yellow.
- This matches the neural pathways in the human retina and cortex.
Pro Tips for Lab Color
- • Delta E threshold: ΔE < 1 is imperceptible; ΔE > 3 is noticeable; ΔE > 10 is different color.
- • Photoshop editing: Convert to Lab mode to sharpen L* channel without affecting color.
- • Color interpolation: Blend colors in Lab space to avoid muddy mid-tones common in RGB.
- • Print matching: Use spectrophotometer Lab values to verify print accuracy.
Why Industrial Designers Use Lab
Calculating "Delta E"
If you print a logo and it looks slightly wrong, how do you measure that "wrongness"? You measure the Lab values of the print vs the digital file and calculate the distance (Euclidean geometry). This distance is called Delta E (ΔE). ΔE < 1: Imperceptible to human eye. ΔE > 3: Clearly visible difference. You cannot do this accurately with RGB values.
Who Uses RGB to Lab?
Print QA Engineers
Verify color accuracy with Delta E measurements.
Paint Formulators
Match pigment mixtures to target colors precisely.
Brand Compliance Managers
Ensure brand colors are consistent across media.
Color Vision Researchers
Study human perception with uniform color metrics.
Frequently Asked Questions
What is CIELAB (Lab)?
It is a color space designed to be 'Perceptually Uniform'. This means a numerical change of 10 units in Lab looks like a visual change of 10 units to the human eye, regardless of the color. RGB does not have this property.
What do L, a, and b stand for?
L* is Lightness (0=Black, 100=White). a* is the Green-Red axis (negative is green, positive is red). b* is the Blue-Yellow axis (negative is blue, positive is yellow).
Why use Lab instead of RGB?
Lab is device-independent and required for accurate color matching (like pigment mixing) and calculating 'Delta E' (how different two colors look).
How is the conversion performed?
It is a multistep process. RGB → Linear RGB → XYZ → Lab. We perform all these steps automatically using the D65 white point.
What is the range of a* and b*?
Technically unbounded, but practically for sRGB colors, they usually range between -128 and +127.
Is 'Lab' different from 'Hunter Lab'?
Yes! This tool uses the modern 1976 CIE Lab* standard. Hunter Lab is an older 1948 standard. They are similar but mathematically different.
Why is Lab preferred for Photoshop manipulations?
Because L* is completely separate from color. You can sharpen the L channel to enhance texture without messing up the color saturation, which isn't possible in RGB.
What is LCH and how does it relate to Lab?
LCH is Lab in polar coordinates: L* (same lightness), C* (chroma/saturation), and h° (hue angle). It's more intuitive for adjusting colors while maintaining perceptual uniformity.
What is CIEDE2000?
CIEDE2000 is an improved Delta E formula that corrects perceptual non-uniformities in Lab, especially in blues and low-chroma colors. It's the current industry standard.
What is CAM16 and how does it compare?
CAM16 is a Color Appearance Model that accounts for viewing conditions (lighting, background). Lab assumes fixed conditions; CAM16 is more accurate for real-world color matching.
Can I use Lab in CSS color()?
Yes! Modern CSS supports color(lab l a b) syntax. Example: color(lab 50% 40 -60). Browser support is growing but not yet universal.
How do I store Lab values as 8-bit integers?
Encode as: L' = L * 2.55 (0-255), a' = a + 128, b' = b + 128. This shifts the -128 to +127 range to 0-255 for image file storage.