Commercial Lighting CCT and CRI: Choosing Colour

Separate light appearance, colour rendering and output

A request for brighter, whiter light can conceal several different problems. The room may have insufficient light at the task, an unwanted colour appearance, or difficulty distinguishing materials. Ask which problem the user sees before changing the fixture specification.

Correlated colour temperature, or CCT, describes the appearance of white light and is expressed in kelvin. Lower values generally appear warmer; higher values generally appear cooler. Colour rendering describes how a light source affects the appearance of objects. CRI is one measure of that rendering, commonly reported as Ra.

DOE's colour-characteristics fact sheet explains why CCT and colour rendering describe different properties. Neither is a substitute for lumen output or illuminance at the work surface. A cooler setting does not, by itself, establish that a desk or rack receives more light.

At the distributor counter, translate the request into separate fields: intended task, preferred CCT, required colour-rendering evidence and required output. Keep those fields separate in the fixture schedule so a substitution does not accidentally change one while matching another.

Choose colour temperature in the actual room

Use these as review steps, not mandatory temperature prescriptions. A building type does not determine one correct CCT. The owner, designer and users should agree on the desired result in the actual environment.

For a sample review, place representative finishes and materials under the proposed light. Compare settings at similar illumination, rather than selecting whichever sample happens to be brighter. Include adjacent retained fixtures and daylight where they will normally be present.

Record the selected setting by room or fixture tag. A verbal instruction such as neutral white is less useful than an agreed numerical setting supported by the approved product data. Keep the sample decision with the submittal so later replacements follow it.

Use CRI as one part of a task-specific requirement

CRI compares the appearance of test colours under a source with a reference. An average score cannot describe every colour shift. Two sources with a similar CRI may therefore produce different results on the particular materials a project needs to evaluate.

For routine circulation, the project may use a simple documented CRI requirement. For colour matching or inspection, tell the specifying engineer what objects must be distinguished. Provide samples of those objects when possible. Do not treat a higher average number as proof that every visual task improves.

The IES discussion of colour specification explains how TM-30 adds information about fidelity and changes in colour saturation. A designer can decide whether additional colour data are necessary. Ask whether those data exist for the proposed configuration before making them a product-selection assumption.

Maintain a clear distinction between evidence and preference. A sample can help users agree on appearance; a measured report supports a performance requirement. If a product page leaves CRI blank, record that as a documentation gap. Do not fill it with a value from another size or visually similar fixture.

Compare the published Allmax configurations separately

The wraparound model table shows why CRI and output should remain separate. The Z-FLWR2R80 row publishes CRI 80 and 2,000 lm; Z-FLWR2R90 publishes CRI 90 and 1,700 lm. Both publish 20 W. These are documented variants, not a universal rule about every change in CRI.

The MFP01 flat-panel table publishes CRI greater than 80 and selectable 3500 / 4000 / 5000 K. The TRF troffer table publishes Ra greater than 80, with its own five CCT settings. Do not transfer one family's available settings to another.

The 4-inch retrofit downlight and 6-inch retrofit downlight publish five CCT settings from 2700 to 5000 K. Their model tables do not publish a CRI value. Request the evidence needed for a CRI specification rather than assuming the selectable temperatures establish colour-rendering performance.

The wraparound table uses the label 5-CCT without enumerating its temperatures. Preserve that distinction when preparing an order. A count of settings does not identify their values or prove a match to an adjacent fixture.

Carry the colour decision into ordering and maintenance

A sample decision can be lost when the order lists only a family name. Include the exact model and the selected CCT in the fixture schedule. Where a family offers CRI variants, identify the intended variant explicitly. Record the corresponding lumen output rather than mixing values from different rows.

• State the room, visual task and any retained lighting that must be considered.
• List the selected CCT and the project's colour-rendering requirement separately.
• Attach the model-specific product data and any requested colour measurements.
• Record sample-review decisions, including materials and viewing conditions.
• Give maintenance staff the approved setting and replacement model information.

Field-selectable CCT should follow the installation instructions and an agreed schedule. Do not leave each installer to choose a setting independently. During handover, check rooms from normal viewing positions and investigate mismatched appearance before treating the project as complete.

Distributors can use RFQ to submit a fixture schedule with the required colour fields. Specifying engineers should identify any measurement beyond the published data and explain the task it supports. That makes the remaining evidence request specific and reviewable.

Related guides

• Field-Selectable LED Wattage and CCT: Ordering Guide
• LED Troffer vs Flat Panel: Commercial Ceiling Guide
• LED Wraparound vs Linear Strip: Commercial Selection

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