The blackest black, measured: Vantablack is #010101

Vantablack absorbs 99.965 percent of the light that falls on it. That figure has been repeated in every piece written about the material since Surrey NanoSystems announced it in 2014, usually alongside a photograph of a crumpled sheet of foil with a hole punched in reality where the coating is. What almost nobody does is convert the number into a color. So we did.

Reflecting 0.035 percent of the light in a scene puts Vantablack at CIELAB L* 0.32 against a white reference in the same light. Encode that through the sRGB transfer function and it comes out as code 1 on a 0 to 255 scale. Vantablack’s hex code, in other words, is #010101. There is exactly one darker value in the entire color space, and it is #000000.

Three things follow from that, and all three of them are more interesting than the 99.965 figure itself. The race for the blackest black finished long before anyone stopped running it. The differences the headlines celebrate are far below the threshold of human vision. And the screen you are reading this on cannot show you any of it, because in a normally lit room its own black is a medium dark gray sitting about a hundred and twenty times above Vantablack.

Every ultra black, converted to a color

Below is each well known deep black, its published absorption figure, the CIELAB lightness that figure implies, and the sRGB code it encodes to. Reflectance here is luminous reflectance: the fraction of visible light coming back, weighted by the eye’s sensitivity, measured against a perfect diffuse white at 1.0. L* runs from 0 for a perfect void to 100 for that white.

Two patterns jump out of that list. The first is how quickly the interesting region ends: everything from Black 4.0 upward is packed into the first three codes of a 256 step ramp. The second is how far the ordinary blacks are from any of it. Black paint from a tin is lighter than Vantablack by 26 lightness units, which is a quarter of the entire visual range from black to white. On a screen it would be rendered as #3F3F3F, a gray most people would not call black at all if they saw it on its own.

Absorption percentages are a terrible way to think about this, because the last fraction of a percent carries almost all of the visual weight while looking like a rounding error. Going from 95 percent to 99 percent moves you 17.7 lightness units. Going from 99 percent to 99.995 percent, a change ten times smaller in stated absorption, moves you only 8.9.

The race ended somewhere around 99.6 percent

The useful question is not which coating reflects least. It is which differences a person can see. We measured every gap in CIEDE2000, the industry’s perceptual color difference metric, where a value of about 2.3 is the classic threshold for a difference a careful observer notices side by side. Our own measurement of that threshold along the lightness axis, taken from real guesses in the game, came out at 3.53 units, so the 2.3 line below is the generous reading.

The vertical line is the 2.3 threshold. Bars that fall short of it are differences that exist in the measurement and not in the seeing.

The headline result is the second bar. When MIT announced a coating that absorbed 99.995 percent of light and called it ten times blacker than anything previously reported, the visual difference from Vantablack was 0.16 CIEDE2000 units. That is about a fourteenth of a just noticeable difference. Stand the two samples side by side under identical light and no human eye can separate them. The factor of ten is real and it is entirely invisible.

We can put a number on where the finish line sits. Solving for the reflectance at which a material lands exactly one just noticeable difference from a perfect void gives 0.44 percent, which is an absorption of 99.56 percent. Anything darker than that is, to a human observer, the same as a hole cut in the universe. Vantablack clears it by a factor of twelve. Black 4.0 clears it by a factor of nine. The MIT coating clears it by a factor of eighty-seven.

That threshold is the most useful number in this piece, because it explains why the ultra black story stopped being a story about vision somewhere around 2013 and became a story about materials science, stray light baffles for telescopes, and an ongoing argument over who is allowed to use which paint. Only one of the coatings above sits far enough from the rest to be visibly different, and it is the cheap one: Musou Black is 3.00 units from Vantablack, the single gap in this entire field that a person could actually pick out.

Your screen is showing you a dark gray

Here is the part that made this worth writing. Every article about the blackest black is illustrated with a picture of the blackest black, viewed on a device that is physically incapable of producing it. This one included.

A display has two sources of light when it is asked for black. It emits some, which on a good OLED is essentially zero and on an LCD is whatever leaks through the panel. And it reflects some, because the front glass is a mirror. Measured screen reflectance for phones and laptops clusters around 4.2 percent, measured on uncoated mobile front glass, and the anti-reflective stacks used on televisions bring that down to about 1.5 percent. That reflected light does not care what the pixels are doing.

Put an OLED phone showing #000000 and a Vantablack coupon side by side in a 150 lux living room, with a sheet of white paper for reference, and the numbers come out like this.

• White paper: 47.7 cd/m². Vantablack: 0.017 cd/m². The phone’s black pixel: 2.005 cd/m².
• The screen is 120 times brighter than the material it is depicting.
• In that room the phone’s blackest pixel sits at L* 24.3, which against paper white is the color #3A3A3A. An LCD laptop comes out at L* 26.1, or #3E3E3E.
• Distance from the screen black to Vantablack: 15.38 units, which is seven separate just noticeable steps.
• Distance from the screen black to ordinary matte black paint from a tin: 1.77 units. Below the threshold. They are the same color.

That last line is the one worth sitting with. In an ordinary room, the darkest thing your display can produce is perceptually indistinguishable from cheap black paint, and is a quarter of the way up the lightness scale toward white.

Dimming the lights does not help

The obvious objection is that the room is too bright. It does not matter. An emissive display asked for black contributes nothing of its own, so both the screen’s black and the Vantablack sample are just the room’s light bouncing off a surface. Halve the illumination and you halve both. The ratio stays at 120 to one at 50 lux, at 500 lux and at 1000 lux, and so does the lightness difference, because L* is defined relative to the white in the same scene. Turning the lights off does not close the gap either, it just removes the white reference and leaves you with nothing to compare.

To land within one just noticeable difference of Vantablack, a screen would need a total surface reflectance of 0.47 percent. That is nine times better than a typical panel and roughly three times better than the anti-reflective coating on a television. It is not a brightness problem or a contrast ratio problem, and no amount of local dimming or HDR certification touches it. It is a problem with the front of the glass.

The 58 codes a lit room deletes

The same reflection floor does something quietly destructive to the bottom of the gray ramp. If the front glass is returning 4.2 percent of the room to your eye no matter what, then every sRGB gray whose own luminance falls below 4.2 percent is buried under it. Counting them: 58 of the 256 gray codes, everything from #000000 up to about #393939, land under the reflection and collapse into a single smudge.

That is 23 percent of the ramp, and if you are looking at that strip under a lamp right now, a good chunk of its left side is probably reading as one flat tone. Move to a dark room and the steps separate. This is the real reason cinema shadow detail evaporates on a phone in daylight, and it is also why comparing two blacks on screen is a pointless exercise. The strip is doing the experiment on you.

It also explains a thing people notice and misattribute. When an image on a page looks washed out and the same image looks rich in a dark room, the file did not change and neither did the display. The floor moved. We covered the neighboring version of this problem in shades of gray, where 256 gray codes reduce to 67 that a person can actually tell apart even under ideal conditions. In a lit room you lose 58 of them before you start.

What black actually is, and what these coatings do

Carbon nanotube coatings are not pigments. Vantablack is a forest of vertical tubes roughly twenty nanometers across, grown on a substrate, with gaps far larger than the tubes themselves. Light entering the forest is not absorbed on first contact so much as trapped: it scatters between tubes, losing a little energy at each bounce, and the probability of finding its way back out before it is spent is very small. The structure is doing most of the work, which is why the material behaves so strangely in photographs. It kills the specular highlights that tell your visual system about shape, so a coated object reads as a silhouette rather than a thing.

This is the same physics as a mirror run in reverse. A mirror is nearly all specular return and almost no absorption. A nanotube forest is nearly all absorption and almost no return of either kind. Ordinary black paint sits in the awkward middle: the pigment absorbs well, but the binder surface still reflects a few percent specularly, and it is that surface reflection, not the pigment, that sets the floor at around five percent. Musou Black’s trick is largely a very rough matte surface that scatters the specular component back into itself rather than at your eye.

Which is a useful reminder that black is not a property of a substance so much as a property of an arrangement. We went through the definitional side of this in is black a color, where the physics answer, the perception answer and the answer your screen uses all disagree. The measurements here are the perception answer, and they say something the physics answer does not: past 99.56 percent absorption there is nothing left to see, and everything after that is a number rather than a color.

What we measured

• Vantablack is L* 0.32 and encodes to #010101. The MIT coating and a perfect void both encode to #000000. sRGB has one code to spare underneath the darkest material ever made.
• The finish line is 99.56 percent absorption. At that point a material is one just noticeable difference from a perfect void, and everything darker is invisible progress.
• The famous ten times blacker result is 0.16 CIEDE2000 units, roughly a fourteenth of a threshold difference.
• Musou Black at 3.00 units from Vantablack is the only gap in the whole ultra black field a person can see, and it is the cheapest material in it.
• A screen showing #000000 in a 150 lux room is 120 times brighter than Vantablack, sits at L* 24.3, and is 1.77 units from ordinary black paint, which is to say the same color.
• That ratio does not change with room brightness. Fixing it needs a screen reflectance of 0.47 percent, nine times better than typical hardware.
• 58 of 256 gray codes fall below a typical screen’s reflection floor and merge into one tone in any lit room.

If you want to feel where your own dark end gives out rather than read about it, the hex guessing mode is the blunt test, because matching a near black by code means working in a region where four adjacent values look identical on the screen in front of you. The guide to hex codes explains why #0A0A0A and #0E0E0E are much further apart in light than they look in notation. For the wider question of how many colors survive the trip from a display to a person, there is how many colors you can see, and the ordinary color memory game is where the dark end tends to embarrass people, because remembering a near black is remembering a hue you never really saw.