ISO 19307:2026

• Abstract:

  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.

• Status: Published
• Publication Date: 18-May-2026
• ICS: 37.100.01 - Graphic technology in general
• Technical Committee: ISO/TC 130 - Graphic technology
• Drafting Committee: ISO/TC 130 - Graphic technology
• Current Stage: 6060 - International Standard published
• Start Date: 19-May-2026
• Due Date: 24-Jul-2026
• Completion Date: 19-May-2026

ISO 19307:2026 is an ISO standard for measuring and representing translucency with a single parameter called translucency alpha. It specifies how to measure flat materials that absorb and scatter light, and how to use that value in appearance-based 3D reproduction workflows, especially those used for 3D printing. The method is aimed at people who need to characterize materials, match printed parts to real objects, or work with translucency in image and 3D file formats.

What does ISO 19307:2026 specify?

ISO 19307:2026 specifies the procedure for measuring a one-dimensional parameter that approximates the translucency magnitude of flat, light-absorbing and light-scattering materials. The document is written for translucency measurement in graphics and 3D reproduction, and it also states that the same parameter can be used beyond additive manufacturing.

The document is organized into:

• Scope
• Normative references
• Terms and definitions
• Requirements
• Test report
• Informative Annex A on scaled models
• Bibliography

Annex	What it covers
Annex A	Matching translucency for scaled models

What are the key requirements of ISO 19307:2026?

ISO 19307:2026 links translucency alpha to measured light transport, then selects the virtual reference material that best matches those measurements. In practice, that means the user measures the material in a defined way, compares the results against a set of reference materials, and reports the corresponding alpha value.

Sample preparation and geometry

Clause 4.2.2 requires a flat, smooth sample with minimum dimensions of 16 mm by 16 mm by 4 mm. That matters because surface roughness and undersized samples can change the measured light transport and distort the result.

Measurement conditions

Clause 4.3 requires three reflectance measurements and one transmission measurement. The specified setup uses ISO 13655 conditions with CIE D50 illuminant, CIE 1931 observer, 45°/0° geometry, black or white backing as stated in the measurement type, and a 2 mm detection aperture. The standard uses different illumination apertures to capture edge loss and transmittance, so the operator must measure both how light spreads laterally and how much passes through.

Virtual reference materials

Clause 4.2.1 defines a set of virtual reference materials with wavelength-independent absorption and scattering coefficients and an isotropic phase function. Each reference material is assigned a translucency alpha value. In practice, this gives a fixed comparison scale instead of relying on a subjective judgment of “more” or “less” translucent.

Selecting the matching reference material

Clause 4.5 chooses the reference material with the smallest deviation from the measured edge-loss difference, transmittance, and color lightness. The clause allows brute-force computation and uses an acceptable lightness variation parameter. For users, this means alpha is not guessed - it is derived by matching measured optical behavior to the closest defined reference.

Simulation of reference data

Clause 4.4 describes how to simulate the required colorimetric quantities for the virtual reference materials using a physical-based path tracer. It uses a regular grid of absorption and scattering values, interpolation for intermediate values, and clipping at the table limits. This is the part that lets implementers build the reference dataset consistently across instruments and software.

Scaling for resized models

Clause 4.6 explains how translucency alpha can be adjusted for scaled models. If a model is resized, the absorption and scattering coefficients are scaled with the model size so the perceived translucency stays similar. That matters in print workflows where a smaller object should still look like the original.

Test report

Clause 5 requires the report to include the measurement devices used and the measured CIELAB colour values. This supports traceability when alpha is used in production, quality control, or matching tasks.

What terms does ISO 19307:2026 define?

• Translucency - the capacity of a material to let light pass while diffusing it so objects behind it are not clearly visible.
• Translucency alpha - a one-dimensional parameter that approximates the translucency magnitude of a flat material that absorbs and scatters light.
• Physical-based path tracer - a Monte Carlo method for numerically solving the radiative transfer equation (RTE).
• RTE - the radiative transfer equation, which describes how radiance changes along a path because of refraction, absorption, emission, and scattering.
• Lateral light transport - light transport within the object that causes blur of textures and fine details seen by the observer.
• Vertical light transport - light transport that allows light from the far side of an object to reach the observer and reveal occluded structures.

Who uses ISO 19307:2026?

ISO 19307:2026 is used in graphic technology and appearance-based 3D reproduction workflows. It is relevant to people developing or operating 3D printing workflows, color measurement setups, and image or 3D tools that need a measurable translucency parameter.

In practice, the standard matters for:

• material characterization of translucent flat samples
• printer calibration and print-material adjustment
• matching printed objects to reference objects
• using translucency alpha in image and 3D file formats
• comparing how translucency changes when objects are scaled

Which standards are used with ISO 19307:2026?

ISO 19307:2026 normatively references ISO 13655, which supplies the spectral measurement and colorimetric computation framework used for the reflectance and transmission measurements.

The term translucency is sourced in the terminology from ISO 20795-1:2013, which provides the definition used in this document.

What does the ISO 19307:2026 document contain?

ISO 19307:2026 contains the scope, the terminology, and a full measurement workflow built around tables, formulas, figures, and a worked scaling concept. Table 1 defines the virtual reference materials, Table 2 sets the minimum sample geometry, Table 3 sets the measurement conditions, and Table 4 gives the selected grid of reference materials for simulation. The document also includes Figures 1 to 3 to show the perception model, the measurement setup, and the matching concept. Formulas 1 to 3 define translucency alpha, the matching step, and the size-scaling adjustment, and Annex A illustrates how scaling changes perceived translucency in practice.

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
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
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
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 130, Graphic technology.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

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
...