A lab orders a light booth. The datasheet says "complies with ISO 3664". The booth arrives, the grey scales go in, and the lab believes its viewing conditions are now standard.
They may be — or they may be standard for the wrong industry. The three documents most often quoted on booth datasheets were written for different jobs, and a booth that satisfies one does not automatically satisfy the others.
Three standards, three purposes
| ISO 3664 | ASTM D1729 | ISO 105-A02 / A03 (via A01) | |
|---|---|---|---|
| Field | Graphic technology and photography | Visual appraisal of colours and colour differences of opaque materials | Grading colour fastness of textiles |
| Reference light | CIE illuminant D50 | Simulated average daylight (D65) generally; D50 for photography and printing | North-sky daylight or an equivalent source |
| Light level | Defined viewing conditions; the critical-comparison condition uses a high level, around 2000 lx | Ranges by material lightness and task (see below) | 600 lx or more |
| Geometry | Defined for prints and transparencies | Defined in the practice | Light at about 45°, viewing about perpendicular |
ISO 3664 was revised in 2025; the 2009 edition is the one still quoted on many datasheets. Its core is D50 for print viewing, with a colour rendering index requirement of 90 or more and an additional metamerism requirement based on virtual metamers.
None of that is wrong for a textile lab. But a fabric graded under D50 is not graded under the daylight condition its buyer probably specified, which in textiles is usually D65.
What textile grading needs
ISO 105-A02 and A03 describe the viewing arrangement for grey scale assessment: original and tested pieces side by side in the same plane, a neutral grey surround of about Munsell N5, illumination from north sky or an equivalent source of 600 lx or more, light falling at about 45°, and viewing roughly perpendicular to the surface. In practice, the "equivalent source" is a D65 daylight simulator in a booth.
ASTM D1729 gives illuminance ranges by material and task. As quoted from the practice: for general evaluation of medium-lightness materials, between 810 and 1880 lx at the centre of the viewed area; for critical evaluation of colour differences in medium-lightness materials, 1080 to 1340 lx; as low as 540 lx for very light materials and up to 2150 lx for very dark ones. Check your copy, as editions change.
Two things follow:
- A booth that delivers 600 lx satisfies the grey scale requirement but may be too dim for critical D1729 work on dark shades.
- A booth designed around 2000 lx for print satisfies the grey scale minimum easily but is above the D1729 range for most textile tasks.
The right answer depends on which documents your customers cite.
Seven things to check before buying
1. Which daylight
If your specifications are textile specifications, you need D65. If you also proof printed packaging or labels, you need D50 as well. Some cabinets offer both.
2. Measured light level at the viewing plane
Ask for the illuminance where the sample sits, not at the lamp. Then measure it yourself with a calibrated lux meter at installation and at intervals. Light level falls as lamps age.
3. Quality of the daylight simulator
A lamp labelled "D65" may simulate daylight well or badly. Ask how the simulator's quality was assessed — colour rendering index and, more importantly for colour matching, a metamerism index such as the method of CIE Publication 51 or ISO/CIE 23603. ISO 105-B02, for example, refers to colour matching lamps in accordance with CIE 51.
4. Interior colour and finish
The booth interior forms the surround. It should be a matt neutral grey that does not reflect or glare. Glossy or tinted interiors change perceived contrast.
5. Geometry
Most booths light from above. Grey scale assessment wants light at about 45° and viewing near-perpendicular. A simple 45° viewing stand inside the booth gets you there; laying samples flat on the floor of the booth does not.
6. Lamp hours
Fluorescent and LED daylight sources drift in both colour and level. Prefer a booth that records lamp running hours, and replace lamps on the manufacturer's schedule rather than when they "look dim".
7. Other sources
If your buyers specify a store illuminant (such as TL84), an incandescent source (illuminant A) or a UV check for optical brighteners, those sources must be in the same booth so that samples can be switched between them without moving.
The room matters too
A booth inside a bright room is not a controlled environment. Switch off or dim the room lights during assessment, keep window daylight out of the booth, and avoid strongly coloured clothing near the cabinet. Screen assessors for colour vision; a colour-deficient assessor in a perfect booth still produces wrong grades.
Matching the booth to the job
| If your main work is… | Prioritise |
|---|---|
| ISO 105 grey scale grading | D65, ≥ 600 lx at the sample, 45° stand, N5-type grey interior |
| Shade matching to buyer standards | D65 plus the buyer's secondary sources (store, incandescent, UV), good metamerism index |
| Print, packaging, labels | D50 and the ISO 3664 conditions |
| Both textiles and print | A cabinet offering D65 and D50, with measured illuminance for each |
TLI-TexLabInstruments manufactures a four- or five-source light assessment cabinet (D65, TL84, A, UV, with optional D50) and a colour viewing station with selectable D50, D65, TL84 and UV-A in its Istanbul workshop.