Short answer
Measurement geometry is the angle at which an instrument lights the sample and the angle at which it collects the reflected light. 45°/0° lights at 45° and views straight down, mimicking how people look at a print while excluding the gloss reflection. d/8° lights from all directions with an integrating sphere and views at 8°, which can include or exclude the gloss. The same sample reads differently in each because they treat the surface reflection differently.
In a 45°/0° instrument the lamp shines on the sample at 45° from the perpendicular and the detector looks along the perpendicular (0°); 0°/45° reverses the path and gives equivalent results. The mirror reflection from the surface leaves at 45° on the far side, away from the detector, so gloss is excluded — much as a reader tilts a glossy page to avoid glare. This is the geometry of the graphic arts: ISO 13655 and every Fogra characterisation data set use 45°/0° (or 0°/45°), and printing densitometers use it too. Some 45° instruments illuminate from a ring of angles around the sample (annular or circumferential) so that directional textures such as brush marks or paper grain do not change the reading with orientation.
A sphere instrument puts the sample at a port of a hollow sphere coated inside with a highly reflective white. Light bounced around the sphere reaches the sample diffusely from every direction (d), and the detector views at 8° from the perpendicular. With a port at the mirror angle either left open as a light trap or closed with a white cap, the instrument can exclude or include the specular reflection — SCE or SCI. Sphere instruments dominate paint, plastics and textiles, where formulation software wants the colour of the material independent of its surface finish, and where SCI makes glossy and matt samples of the same colourant comparable.
The difference is the surface reflection and how the sample's texture interacts with the light. On a matt print, 45°/0° and sphere SCE readings are close. On a glossy sample, SCI adds the few per cent of light reflected at the surface back into every wavelength, so dark colours read lighter and less saturated than they look. On textured materials, directional illumination casts micro-shadows that diffuse illumination fills in. Differences of a few ΔE00 between geometries on the same sample are normal, which is why a colour specification is incomplete without its geometry and why data from different geometries should never be mixed in one tolerance check.
Geometry is not the whole description. The measured area must be large enough to average over halftone dots, fibres or texture, but not so large that it takes in edges. For directional 45° instruments, rotating an anisotropic sample (brushed metal, textiles, paper with a strong grain) changes the result unless the illumination is annular. Sphere instruments have their own subtleties: the sphere's coating ages, and the specular port has a finite size, so 'excluded' specular light is only what falls within that port. Recording instrument model, geometry, aperture and specular mode with every measurement is the simplest defence.
| Geometry | Illumination | Viewing | Gloss (specular) | Typical use |
|---|---|---|---|---|
| 45°/0° or 0°/45° | Directional at 45° (or 0°) | 0° (or 45°) | Excluded by geometry | Print, graphic arts, visual-like QC |
| 45°a:0° (annular) | Ring of 45° beams | 0° | Excluded | Textured or directional samples |
| d/8°, SCI | Diffuse, integrating sphere | 8° | Included | Formulation; comparing glossy and matt |
| d/8°, SCE | Diffuse, integrating sphere | 8° | Excluded through light trap | Appearance checks on glossy parts |
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactStrong evidence
In 45/0 geometry the specimen is illuminated at 45° to the normal and viewed along the normal; 0/45 reverses this. In d/0 or 0/d geometries an integrating sphere lights or collects diffusely, and the specular component can be included or excluded.
Source: Precise Color Communication; CIE 015:2018 Colorimetry, 4th edition
FactStrong evidence
The Fogra characterisation data sets for offset printing record their measurements as D50, 2° observer, 45/0 geometry and white backing according to ISO 13655.
Source: FOGRA51 characterization data (premium coated offset, ISO 12647-2:2013); FOGRA39 characterization data (coated offset, ISO 12647-2:2004/Amd 1)
StandardStrong evidence
ISO 12647-2:2013 specifies substrate colour measurement according to ISO 13655 with D50, the 2° observer and 0:45 or 45:0 geometry.
Source: ISO 12647-2:2013 Graphic technology — Process control … — Part 2: Offset lithographic processes; ISO 13655:2017 Graphic technology — Spectral measurement and colorimetric computation for graphic arts images
Colourwise interpretationModerate evidence
Colour values taken with 45°/0° and sphere geometries on the same glossy or textured sample should not be compared against one tolerance.
Based on: Follows from the different treatment of specular reflection and texture by the two geometries, as described by the CIE and instrument makers.
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.