Munsell N5 is a neutral grey with no color cast that sits, to the human eye, halfway between black and white. Photographers and filmmakers know the same reference as 18% grey. It is the color for rooms where color is judged.
The Munsell color system in brief
The American painter and teacher Albert Munsell developed his color system in the early twentieth century. He described every color with three properties:
- Hue: the color itself, such as red, yellow or blue.
- Value: the lightness, from 0 (black) to 10 (white).
- Chroma: the saturation, from grey to intensely colored.
The steps in the system are equal to the eye, not to a measuring instrument. A step from 4 to 5 looks as large as a step from 7 to 8.
What does the code N5 mean?
The N stands for neutral: no hue and no chroma. The number is the value. N0 is black, N10 is white, and to the eye N5 sits in between.
That midpoint is not where you would expect it. An N5 surface reflects roughly 20% of the light, not 50%. Our eyes do not respond to light in a linear way: a surface that reflects half the light already looks almost white.
Munsell N5 and 18% grey
In photography and film this reference is called 18% grey, familiar from grey cards and light meters. In the Munsell system it is called N5. In practice the two are used as the same middle grey: both have an L* of around 50, with a* and b* at zero. Strictly speaking N5 is a fraction lighter, but that difference only shows when you hold both samples directly side by side.
What matters more than that last decimal of lightness is that the grey is truly neutral. A grey with a slight blue or warm cast has the right lightness, but it is not a reference.
When can you see a color difference?
Color difference is expressed as ΔE (Delta E). As a rule of thumb:
- Below 1: not visible, even side by side.
- 1 to 2: visible to a trained eye, side by side.
- 2 to 3.5: visible to most people, side by side.
- Above 5: clearly a different color.
With grey, the eye is more sensitive to a color cast than to a small difference in lightness. For a wall it is therefore more important that a* and b* are close to zero than that L* is correct to the decimal.
How neutral is Grey Paint?
Grey Paint is mixed to 18% grey. The latest measurement:
| L* | a* | b* | ΔE | |
|---|---|---|---|---|
| Ideal 18% grey | 49.50 | 0 | 0 | 0 |
| Grey Paint | 49.09 | -0.33 | -0.43 | 0.7 |
| A widely sold grey card | 50.14 | -1.09 | -1.88 | 2.3 |
ΔE is measured against ideal 18% grey. With a ΔE of 0.7, the difference between Grey Paint and ideal 18% grey is not visible. The measured grey card has the right lightness, but a slight cool cast that shows next to a neutral reference.
Why neutral grey on the wall?
Your eyes adapt to their surroundings all the time. If your screen stands in front of a colored or overly bright wall, your brain compensates and you see the colors on your screen differently from what they are. A neutral middle grey wall gives your eyes a fixed point of reference.
That is why neutral middle grey is the usual choice in color grading suites, photography studios, print shops, design agencies and home cinemas.
Can you have it mixed at a hardware store?
In practice the result disappoints. Mixing machines have a margin of error, and the base paint varies from one production batch to the next. The result looks neutral, but often has a cast you only notice next to a true reference.
Grey Paint is freshly mixed per order and checked against its Lab* values, so the color stays the same batch after batch.
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