Color Match Approval Under Multiple Light Sources
Standardized visual evaluation of colour matches across D50 (5000K), D65 (6500K), and Illuminant A (warm-white) light sources. This procedure ensures colour consistency meets quality specifications before batch release.
To provide a repeatable, objective procedure for visually approving colour matches under standardized lighting conditions. This eliminates subjective judgment errors caused by varying ambient light and ensures that production batches conform to the approved colour standard.
This SOP applies to all incoming paint batches, touch-up kits, and production colour samples that require visual approval under multiple light sources. It covers the use of a standardized light booth, the three mandatory illuminants (D50, D65, and A), and the documentation of approval or rejection.
- Never stare directly into the light booth lamps when switched on. Prolonged exposure to high-intensity light can cause eye strain or afterimages. Allow 2 minutes of adaptation before evaluating.
- Some colour samples may contain volatile compounds. Ensure the work area is ventilated if samples are freshly mixed.
- Only trained personnel should replace or service light booth bulbs. Disconnect mains power before any maintenance.
- Calibrated colour light booth (e.g., GretaMacbeth SpectraLight QC or equivalent) with D50, D65, and Illuminant A sources
- Neutral grey mask (Munsell N5 or N7) to isolate samples
- Approved colour standard (reference panel)
- Production sample panel
- Approval log sheet or digital form (ServiceGrid CMMS task)
- Blue wool fading scale (optional, for UV assessment)
Ensure the booth is clean and that all lamps are 500+ hours since last calibration. Turn on D50 (5000K) light source. Place the reference standard and the production sample side-by-side on a neutral grey mask inside the booth. Orient both panels with the same grain or direction.
Allow the technician’s eyes to adapt for 2 minutes under D50. View the pair at approximately 45° to the surface, from a distance of 30–45 cm. Look for differences in hue, saturation, and lightness. Record a pass (P) or fail (F) for the D50 condition on the log.
Change the light source to D65 and wait 30 seconds for stabilization. Re-evaluate the same pair. Pay special attention to metamerism – if the match appears different under D65 than under D50, the colour will shift in daylight environments. Record the result.
Select the incandescent (Illuminant A) source. After 1 minute of adaptation, inspect the pair. Many colour mismatches become visible under warm light. Note whether the match holds. Record pass/fail.
If all three sources show no visual difference (Pass), mark the batch as APPROVED. If any source shows a clear mismatch (Fail), reject the batch and note which light source(s) caused the failure. Do not approve a batch that fails under any mandatory illuminant.
Complete the approval log with the following: date, batch/lot number, operator name, results per light source (P/F), and final disposition. Attach the signed record to the batch paperwork. In ServiceGrid, log the task as "Colour Approval – Batch [ID]" and attach the digital form.