What Is Reflectance? The Science Behind True Blackness
Black materials are often associated with the idea of "absorbing light."
In reality, the main reason we perceive something as black is that its reflectance in the visible light range is low.
Reflectance is the proportion of light striking an object that gets reflected back.
It's usually expressed as a percentage, the lower the value, the less light is reflected, and the blacker the surface appears to the human eye.
For example, if 1,000 photons strike a material that transmits almost no light, and only one of them is reflected, the reflectance is 0.1%.
Most of the remaining light energy is absorbed within the material and ultimately converted into heat or weak re-emission.
Our ultra-low-reflectance material, Musou Black Fabric KIWAMI, achieves
an average visible-light reflectance of just 0.1%, an extraordinarily low figure,
and is used in photography, R&D, and other applications where unwanted reflected light needs to be suppressed.
So what does this figure of "0.1%" actually mean in physical terms?
And why does it serve as proof of being "the blackest in the world"?
To understand the answer, we need to look at where the energy goes when light strikes an object. In this article, we'll take a look at the scientific essence of "blackness."
Left: A typical black background fabric ｜ Right: Musou Black Fabric KIWAMI
The Relationship Between Reflectance, Absorptance, and Transmittance
When light strikes an object, its energy is divided into three components:
・Reflectance (R): the proportion of light reflected
・Absorptance (A): the proportion of light absorbed inside the material
・Transmittance (T): the proportion of light that passes through the material
By the law of conservation of energy, these three quantities satisfy the following relationship:
R (Reflectance) + A (Absorptance) + T (Transmittance) = 100%
For example, Musou Black Fabric KIWAMI has a reflectance of roughly 0.10%.
Since its transmittance is essentially 0%, nearly all of the remaining light energy, 99.9%, is absorbed.
As a result, the human eye perceives it as an extremely black material.
Reflection Comes in Two Forms: Specular and Diffuse
Reflection isn't a single phenomenon, there are broadly two types.
Specular Reflection (Mirror Reflection)
This is when incident light reflects in a single, consistent direction, as with a mirror or polished metal.
The stronger this reflection, the more likely glare and unwanted reflections (glare) are to occur.
Diffuse Reflection
On surfaces like paper or fabric, light scatters and reflects in many different directions.
Even ordinary black fabric produces diffuse reflection, and this scattered light is what undermines true blackness.
Ultra-low-reflectance materials achieve high blackness performance across all reflection angles by reducing both specular and diffuse reflection.
How Is Reflectance Measured?
Reflectance isn't something you can judge by eye alone, it's measured quantitatively using dedicated instruments.
One of the most widely used methods is spectrophotometry using an integrating sphere.
The sphere collects and homogenizes the light reflected from a sample across the entire hemisphere, allowing for highly precise measurement.
This approach makes it possible to objectively evaluate the reflectance of a wide range of materials, from glossy surfaces to diffusely scattering ones.
At Musou Black, we use the following instruments to measure reflectance:
・Portable colorimeter: Konica Minolta CM-25d
・UV-Vis-NIR spectrophotometer: JASCO V-780
Reflectance Values Depend on Measurement Conditions
Reflectance readings vary depending on the conditions under which they are measured.
When comparing figures published by different manufacturers, it's essential that the following conditions match:
・Angle of incidence (AOI)
・Wavelength range measured
・Whether an integrating sphere is used
・Whether specular reflection is included
・Measurement standard (ISO, ASTM, etc.)
At MUSOU BLACK, we measure at an angle of incidence (AOI) of 8°,
meaning light is directed at the sample surface at an 8° angle.
Standardizing measurement conditions in this way makes it possible to accurately compare performance across different materials.
The Difference Between Average Reflectance and Spectral Reflectance
Reflectance is commonly expressed in two ways: "average reflectance" and "spectral reflectance."
Average reflectance is the value obtained by averaging reflectance over a defined wavelength range (for example, the visible range of 400–700 nm).
It's often used to compare product performance at a glance.
On the other hand, spectral reflectance shows reflectance as a function of wavelength.
The human eye is most sensitive to yellow-green light around 550 nm, but the blackness we actually perceive is determined by the reflectance distribution across the entire visible spectrum.
This means that even materials with identical average reflectance can differ in appearance and suitable applications depending on the shape of their spectral reflectance curve.
Musou Black Fabric KIWAMI and VL Flock Sheet both maintain low spectral reflectance across the entire visible range, which is why they deliver high blackness performance under a wide variety of viewing angles and lighting conditions.
Total hemispherical reflectance of MUSOU BLACK's products
Why Is a Reflectance of 0% So Difficult to Achieve?
A material with "0% reflectance", one that reflects none of the incident light whatsoever, would, in theory, appear as a perfect black.
In practice, however, achieving 0% reflectance in a real material is extremely difficult.
In optics, an idealized object that absorbs all incident light is called a black body.
A black body is a theoretical model in physics, and no real material can achieve a perfect black body.
Why 0% Reflectance Is So Hard to Achieve
The main reasons include the following phenomena.
Fresnel Reflection
At the boundary between air and a material, differences in refractive index inevitably cause some light to be reflected.
This is known as Fresnel reflection, and reducing it completely to zero is extremely difficult.
Microscopic Surface Roughness
Surfaces have nanometer- to micrometer-scale irregularities that cause light to scatter.
Internal Scattering
Pigments, fibers, crystal structures, and similar features scatter light inside the material, and some of that light can find its way back out.
Intrinsic Optical Properties of the Material
Optical constants such as refractive index and absorption coefficient impose a physical limit on how completely light can be absorbed.
For this reason, the development goal for today's ultra-low-reflectance materials is to bring reflectance as close to zero as physically possible, rather than to eliminate it entirely.
Ultra-Low-Reflectance Materials Around the World
In recent years, numerous ultra-low-reflectance materials have been developed using nanotechnology.
A well-known example is material grown from densely packed carbon nanotubes (CNTs), which achieves a reflectance below 0.1% in the visible range.
However, such materials face challenges related to manufacturing cost, durability, and workability, making them unsuited to mass production and largely inaccessible to general consumers.
As a result, recent development efforts have focused on materials that combine practicality with ultra-low-reflectance performance.
Musou Black Fabric KIWAMI is an ultra-low-reflectance fabric that achieves an average visible-light reflectance of 0.1%.
It's flexible and easy to work with, and is used across a wide range of applications including photography, exhibitions, and optical experiments.
We've also developed a brushable water-based acrylic paint, Musou Black Paint, which achieves a reflectance of 1.1% or lower when brushed on and 0.6% or lower when airbrushed, and is widely used in model-making and photography.
The world's blackest fabric: Musou Black Fabric KIWAMI
Applications of Low-Reflectance Materials
Low-reflectance materials play an important role in any field where unwanted stray light needs to be suppressed.
Photography & Film Production
Used for studio backgrounds and inside camera equipment, these materials reduce flare and unwanted reflections, allowing a subject's true color and form to be captured clearly.
Optical Instruments & R&D
In telescopes, microscopes, laser systems, spectrometers, LiDAR, and similar equipment, even a small amount of stray light can affect measurement accuracy, making ultra-low-reflectance materials essential.
Exhibitions & Museums
Used in display cases and as background material, these products suppress reflections from lighting and let exhibits themselves stand out more beautifully.
Science Education & Research
In optical experiments and teaching materials, suppressing unwanted reflection makes it possible to observe the behavior of light more accurately.
Infrared & Sensing Equipment
In the near-infrared and infrared ranges, low-reflectance materials are widely used to control stray light and improve sensor performance.
Frequently Asked Questions About Reflectance
Q. What are the benefits of low reflectance?
A. Reducing unwanted reflected light suppresses glare and flare in photography and reduces stray light in optical instruments.
This leads to improvements in image quality, measurement accuracy, and visibility.
Q. How high is the reflectance of white materials?
A. A typical white paint has a reflectance of roughly 70–90%, and a white reference standard used in optical measurement can reach 98–99%.
That's roughly 1,000 times higher than an ultra-low-reflectance material with a reflectance of 0.10%.
Q. What's the difference between reflectance and absorptance?
A. Reflectance is the proportion of light reflected at the surface, while absorptance is the proportion absorbed inside the material.
For opaque materials, transmittance is essentially 0%, so "reflectance + absorptance ≈ 100%."
Q. Why does blackness matter?
A. In optics, suppressing unwanted light translates directly into better measurement accuracy and image quality.
Low-reflectance materials play a vital role in photography, observation, measurement, automotive applications, safety technology, and many other fields.
Summary
Reflectance is a physical quantity that indicates how much of the light striking an object is reflected back.
Light interacting with a material is divided into reflection, absorption, and transmission,
and by the law of conservation of energy, "reflectance + absorptance + transmittance = 100%."
Reflection itself takes two forms, specular reflection and diffuse reflection, and ultra-low-reflectance materials achieve their high blackness performance by reducing both.
Achieving 0% reflectance in a real material remains difficult, but advances in nanotechnology and materials design have made it possible to produce practical, world-class ultra-low-reflectance materials with reflectance around 0.1%.
MUSOU BLACK's world-leading black materials, Musou Black Fabric KIWAMI and Musou Black Paint, are products engineered to minimize reflectance for their respective applications.
They're used across a wide range of fields that require control over unwanted light, photography, optical instruments, automotive, exhibitions, R&D, art, and more.
Reflectance isn't simply a measure of "blackness", it's an important physical quantity for evaluating a material's ability to control light.
Choosing the right material can lead to improvements in image quality, measurement accuracy, safety, and more.
At MUSOU BLACK, we solve light-reflection problems across every field.
From visible light to the near-infrared range, feel free to bring us your reflectance-related challenges.
Left: VIS Absorbing "VL Flock Sheet" | Right: NIR Absorbing "IR Flock Sheet"
Photographed with a near-infrared camera
VL Flock Sheet vs. IR Flock Sheet: Choosing Darkroom Materials to Simulate Space
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MUSOU BLACK's World's Blackest Materials
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