ISO 19307:2026

International
Standard
ISO 19307
First edition
Graphic technology — Measurement
2026-05
and one-parameter representation
of translucency
Technologie graphique — Mesurage et représentation à un
paramètre de la translucidité
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 2
4.1 Background of translucency perception .2
4.2 Determining translucency alpha .3
4.2.1 General .3
4.2.2 Material and Sample Preparation .4
4.3 Colorimetric measurement.4
4.4 Simulating colorimetric measurements of virtual reference materials .5
4.5 Computing translucency alpha for real materials.6
4.6 Adjusting translucency alpha for scaled models .7
5 Test report . 8
Annex A (informative) Matching translucency for scaled models . 9
Bibliography .11

iii
Foreword
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iv
Introduction
Advances in 3D printing allow the combination of multiple printing materials with different optical
properties into a single object at a very high resolution. This allows the reproduction of not only the object's
shape but also its visual appearance attributes, in particular colour and translucency.
Many existing 3D file formats encode spatially resolved information of (albedo) colour and opacity of an
object as a RGBA texture mapped to its 3D geometry. This information is widely used in rendering, where
the RGB colour information is typically interpreted as device independent standard RGB and A (also called α)
as a blending or mixing parameter to produce transparent overlays in image composition assuming additive
colour mixture.
Using an additive colour mixture model is simple, computationally efficient and robust for on-screen display,
but it has severe shortcomings, i.e. light is altered by matter subtractively, not additively, i.e. many real
transparent materials cannot be described by this interpretation. As a result, renderings employing α as
an additive mixture parameter are suitable for illustrative purposes rather than accurately simulating the
appearance of real objects.
Therefore, it is highly desirable to capture perceived translucency of real objects within a single parameter,
foremost because it allows the seamless continued use of existing image and 3D file formats, and it is
supported by various existing 3D design and image manipulation tools.
For the purpose of reproducing translucent objects by 3D printing, a few properties of α are desired.
— α is linked to a measurable quantity. Only then, can α be assigned to real materials via measurements
and print material arrangements can be adjusted to match this quantity.
— For print reproductions, a perceptually uniform scale for α is important, allowing the minimization
of perceived errors rather than physical ones. The viewing conditions for this scale agree with the
RGB conditions to ensure consistency of colour and translucency. In colour printing, the viewing/
illuminating geometry is specified by the International Color Consortium and is supported by colour
and spectrophotometric measurement devices employed in graphic arts, which are used to calibrate the
printers.
— If an object made of a translucent material is scaled (most commonly shrunk) for printing, it is desirable
that average light transport distances can be adjusted accordingly to preserve perceptual translucency
cues. This is demonstrated in Annex A. Therefore, α should be adjustable to the print size in relation to
the original object size in an intuitive, predictable and computationally efficient way.
— For design purposes, the absence of cross-contamination between the chromatic channels (chroma and
hue) and α is important, i.e. that changing the chromatic channels has no effect on perceived translucency
and vice versa, for the specified viewing conditions.
Translucency alpha is a one-dimensional parameter defined for all materials, without imposing constraints
on their spectral refractive index, absorption and scattering properties, or phase functions. Translucency
alpha is assigned to a material by selecting a virtual reference material matching in transmittance and edge
loss when measured as described on a 4 mm flat tile (reference thickness). The virtual reference materials
are defined by wavelength-independent scattering, absorption and refractive indices as well as an isotropic
phase function.
The bigger the intrinsic optical properties deviate from the optical properties of the virtual reference
material the bigger will be the deviation of perceived translucency for samples with thicknesses other
than 4 mm. Real material can change in scattering phase function and can possess wavelength-dependent
scattering and absorption (the virtual reference materials are defined by an isotropic phase function and
wavelength independent absorption and scattering). This is the limitation of using just one parameter to
describe the magnitude of translucency.
It is worth mentioning that various publications show that the degree of perceived translucency is judged
[2],[3]
predominantly at thin structures, i.e. it is plausible that the virtual reference material that best mimics

v
translucency cues caused by lateral and vertical light transport within a real material is selected based on
measurements on thin structures.

vi
International Standard ISO 19307:2026(en)
Graphic technology — Measurement and one-parameter
representation of translucency
1 Scope
This document specifies the procedure for the measurement of a one-dimensional parameter approximating
the translucency magnitude of flat materials that absorb and scatter light. This one-dimensional material
property is called ‘translucency alpha’ and can be used in appearance-based 3D reproduction workflows
ensuring accurate translucency.
While the measurement conditions and virtual reference materials used to define translucency alpha are
designed for 3D printing workflows, the use of translucency alpha is not limited to reproducing objects with
additive manufacturing technologies.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 13655, Graphic technology — Spectral measurement and colorimetric computation for graphic arts images
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
translucency
capacity of a body of material to allow the passage of light, yet diffusing the light so as not to render objects
lying beyond the body clearly visible
[4]
[SOURCE: ISO 20795-1:2013, 3.15]
3.2
translucency alpha
α
one-dimensional parameter approximating the translucency magnitude of a flat material that absorbs and
scatters light
Note 1 to entry: It should be noted that the Alpha channel (A) in RGBA is not defined in any standard. It is often used as
a weighting parameter between image overlays which has no precise physical correlate. Translucency alpha α can be
used as the Alpha channel (A) in RGBA.

3.3
physical-based path tracer
Monte Carlo method for numerically solving the radiative transfer equation (RTE)
Note 1 to entry: The radiative transfer equation (RTE) describes the change in radiance along a path due to refraction,
absorption, emission, and scattering in participating media
3.4
lateral light transport
transport of light within an object responsible for radiance emitted from a surface with normal n �facing
T
the observer in a direction p satisfying np>0 due to incident radiance R arriving from a direction g
1 1 1
T
with ng <0.
T
No
...