Delta-E & the Just-Noticeable Color Limit

One number for how different two colors are, and why the answer depends on the formula.

Short answer: Delta-E (ΔE) is a single value that measures the difference between two colors in a perceptual space. A ΔE of about 1 (CIEDE2000) is commonly treated as the just-noticeable difference, the smallest gap a person can typically catch. Under the older CIE76 formula the just-noticeable value is larger, around 2.3. Same colors, different formula, different number.

Color 1 Color 2

ΔE₀₀ = -- · ΔE₇₆ = --

ΔE computed in CIELAB (D65). ΔE00 ≈ 1 is the just-noticeable threshold; under ~2.3 is hard to tell apart side by side.

What Delta-E measures

ΔE collapses the difference between two colors into one number, computed in a color space designed so the number tracks how different the pair looks rather than just how far apart their raw coordinates sit. The usual space is CIELAB, where a color is placed by lightness (L*) and two axes that run green to red (a*) and blue to yellow (b*). In the original formula this is simply the straight-line distance between the two points. Zero means identical; the larger the ΔE, the more clearly the two colors read as different. That makes it the working yardstick for print matching, display calibration and quality control, anywhere close enough needs to be an actual figure.

What counts as just noticeable

The just-noticeable difference is where two colors stop looking the same. Under CIEDE2000, that threshold is commonly placed at a ΔE of about 1: below 1 the difference is generally imperceptible, and a ΔE of roughly 1 to 2 requires close inspection to see. Under the older CIE76 formula the same perceptual boundary lands higher, near 2.3. This is exactly why the formula has to be named beside any ΔE figure, because a bare "ΔE of 2" means one thing in CIE76 and something quite different in CIEDE2000.

A rough scale of Delta-E (CIEDE2000)

ΔE	What it means
≤ 1	Imperceptible to most viewers
1 to 2	Perceptible on close inspection, or by a trained eye
2 to 3.5	Noticeable, the commercial "different enough" range
> 5	Reads as a clearly different color

Treat these as guidance, not hard cutoffs, because perception varies between people and with lighting, size and surroundings.

The formula family

ΔE is not one equation but a small family, each refining the one before it. CIE76 is the plain distance in CIELAB. CIE94 adds weighting so that differences in lightness, chroma and hue are scaled more like the eye sees them. CIEDE2000 goes further, adding an extra rotation term to handle the troublesome blue region and interactions between chroma and hue. The later formulas are more accurate but more complex to compute, which is the trade-off you are choosing between when you pick one.

Formula	Year	Just-noticeable ΔE	Notes
CIE76	1976	~2.3	Simple Euclidean distance in CIELAB
CIE94	1994	~1 to 2	Adds lightness, chroma and hue weighting
CIEDE2000	2001	~1	Current reference; corrects the blue region

Why CIE76 and CIEDE2000 disagree

The gap between the formulas is not a rounding quirk; it comes from the eye itself. Human color sensitivity is non-uniform, and we resolve some regions of color space far more finely than others. The original CIE76 formula treats the space as uniform, so it over- or under-states differences depending on where the colors sit, and it is famously off in the blues. CIEDE2000 adds correction terms to better match perception, which is why it is now the standard reference and why it generally reports a smaller just-noticeable value than CIE76. The definitive implementation, published by Sharma, Wu and Dalal in 2005, is what most modern tools follow.

Where Delta-E is used

The reason all this precision matters is that industries have to agree on when a color is close enough to ship. Printers and packaging houses set a ΔE tolerance so a brand color looks the same across runs and substrates; display and camera makers use it to calibrate and to grade panels; textile and paint suppliers use it to accept or reject a batch. A brand may demand a CIEDE2000 ΔE under 1 or 2 on its signature color, while a general commercial tolerance often sits nearer 3 to 5. In every case, ΔE turns a subjective argument about matching into a number both sides can check, which connects it directly to how contrast is quantified and to the limit of colors we can tell apart.

Find your own just-noticeable difference

ΔE is a number for something you can feel directly. In Huefork, two shades sit side by side and you decide whether they are the same or different, the gap narrowing until you reach your own limit. It is a hands-on way to sense where your personal just-noticeable difference falls, the human counterpart to a ΔE reading.

Play Huefork →

Frequently asked questions

What is Delta-E?

Delta-E (written as Delta E) is a single number that measures the difference between two colors. It is calculated in a perceptual color space, usually CIELAB, so the number roughly tracks how different the two colors look, not just how far apart their raw values are. Larger Delta-E means a bigger visible difference.

What Delta-E is 'just noticeable'?

It depends on the formula. Under the modern CIEDE2000 formula, a Delta-E of about 1 is commonly treated as the just-noticeable difference: below 1 the difference is generally imperceptible, and 1 to 2 needs close inspection. Under the older CIE76 formula the just-noticeable value is larger, around 2.3.

Why do CIE76 and CIEDE2000 give different numbers?

Human color sensitivity is not uniform, and we resolve some regions of color space more finely than others. CIE76 treats the space as uniform and so misjudges differences in some regions, especially the blues. CIEDE2000 adds corrections to better match perception, which is why the same pair of colors can score a different Delta-E under each formula.

Can I see a Delta-E of 1?

Roughly at the edge. A Delta-E near 1 (CIEDE2000) sits at the just-noticeable boundary: many people cannot see it, and those who can usually need side-by-side, close inspection. Differences of about 2 to 3.5 become noticeable in commercial contexts, and above roughly 5 the colors read as clearly different.

What Delta-E is acceptable for print or brand color matching?

It depends on how critical the match is. For demanding brand and proofing work, a CIEDE2000 Delta-E under about 1 to 2 is the usual target, since that sits at or just above the just-noticeable boundary. Many commercial print and packaging tolerances accept roughly 3 to 5, where a difference is visible on inspection but not obtrusive in normal viewing.