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LED Modules: What Features Determine the Quality of LED Modules for Signage?
3 Feb 2026
Similar to LED strips, LED modules also feature qualities that help sign makers and lighting designers find the right module for the job.
In this article, we shed light on the concepts of Colour Correlated Temperature (CCT), Colour Rendering Index (CRI), and Standard Deviation of Colour Matching (SDCM).
CCT: Colour Correlated Temperature
Colour-correlated temperature indicates the colour hue or tone of the LED light source itself. Typically measured in Kelvin (°K), most CCT LEDs range from warm white at 2700°K to bright pure white at 6000°K.
For installers, consider the type of signage application and how colour temperature might affect the sign's aesthetic. For example, using a warm white, 3000°K LED module behind a white acrylic face may appear creamier than snow white.
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CRI: Colour Rendering Index
The Colour Rendering Index is a rating system that gauges how well a lighting source reproduces the true colours of objects as they appear in natural light.
This system ranges from 0 to 100 across 8 main colour samples, with 0 indicating extremely poor natural colour representation and ratings closer to 100 representing the most realistic colour representation.
For installers, depending on your intended installation, most signage installations may require an LED module with a CRI ≥ 75, particularly those with backlit lighting. In contrast, a retail display may require LED modules with a CRI ≥ 90 to accentuate the display's vibrant colours.
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TM-30 Colour Rendering
As a modern alternative to the CRI system, a system derived from the TM-30 system is available. This system encompasses 99 colour samples, designed to be inclusive of skin tones, textiles and colours from natural objects. This system uses two scores, the fidelity index and gamut index and uses a colour vector graphic to define quality.
The Fidelity chart measures how accurately a light renders the TM-30 colours compared to natural light, whereas the Gamut index measures the vibrancy or saturation of colours.
In essence, a CRI will tell you whether a light is of good quality based on the 8 main colour samples, whereas the TM-30 will tell you exactly how colours will look under this light.
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SDCM: Standard Deviation of Colour Matching
The SDCM rating system corresponds to the MacAdam Ellipses system, and the 1-step to 7-step scale indicates the degree of colour consistency. The general rule of thumb is that under 3 steps, consistency is quite close and barely perceptible to the human eye; between steps 3 and 5, these can be more noticeable; and 5 steps and above are typically very inconsistent and noticeable.
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The key takeaway here is to consider the installation application: if it is for retail or luxury, perhaps an SDCM with 3 steps. If the application is more focused on office lighting or commercial interiors, 3–5 steps are attainable, whereas 5 or more steps may be more appropriate for larger industrial settings where aesthetics are less of a focus.
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If you’d like to learn more about the quality features and design aspects you need to find the right LED module for your next project, check out our latest blog on understanding the various types of LED modules and how they are designed to meet different installation needs here.
If you have any questions, speak to our team at PSA! We have three warehouses across Australia, Melbourne, Brisbane and Perth, with technical support teams to answer any questions that may arise ahead of your next purchase.
Send any questions to our contact page here or speak with our team directly on 1800 632 693.
