A white light's ability to maintain colour uniformity is crucial and may make or break a lighting project. However, it is also one that is frequently disregarded. Read on to learn what colour consistency is and, more importantly, how to consistently achieve excellent colour constancy.
What, in plain English, is colour consistency?
In general, the blue/green and green/magenta axes make it simple to differentiate between colour variations. One light could seem more "green" or "bluer" than another, for example, as you compare them.
Colour temperature, which is measured in Kelvin (k), may be used to identify the difference between blue and yellow. Depending on the application, different levels of colour fluctuation may be allowed, however when it comes to warm white LED light, +/-75K is typically recognized as the cutoff point for identifiable colour temperature. On the other side, the threshold for cold white or standard white is +/-150K.
In contrast, green/magenta fluctuation may be identified using a measure that is less well-known than Kelvin. Duv is the name of this metric. A neutral light source is indicated by a value of 0.000 Duv. On the other side, a movement toward the hue magenta is indicated when Duv is negative. On the other hand, when Duv is in positive, a colour shift to green is visible. In general, Duv values that differ by more than 0.002 are visible to us.
Keep in mind that Duv variation is commonly disregarded for a variety of reasons, despite the fact that it is more obvious than CCT variation. Don't forget to ask the supplier for Duv tolerance figures if colour uniformity is a crucial component for your application.
What are MacAdam Ellipses or SDCM?
Standard Deviation Colour Matching is referred to as SDCM. Some manufacturers choose utilizing the SDCM or MacAdam ellipses metrics to quantify colour constancy. These two phrases both refer to the same measure and idea. "Step" is the unit of measurement in this situation. The hue variation increases with the number of stages.
A 5-step SDCM is regarded as an adequate colour consistency for ordinary applications. In contrast, the threshold is often a 3-step SDCM for demanding applications. It's likely that in some situations even lower colour consistency requirements apply. However, once the consistency is as low as 1 or 2 SDCM, the majority of individuals probably cannot detect colour variation.
So, which metric—CCT, Duv, or SDCM—is better?
Due to two factors, SDCM is thought to be superior to Duv and CCT. One is that it can collect variance in both the blue/yellow and green/magenta directions and condense that variation into a single value. That may be helpful since colour discrepancies occasionally affect both dimensions rather than just one. Two, at low colour temperatures, a 100K fluctuation is thought to be larger. The outstanding aspect of SDCM is that it recognizes this reality and performs the necessary modifications in accordance with the colour temperature. The biggest disadvantage is that many manufacturers still do not pay enough attention to colour difference, and as a result, they are probably not familiar with this specific measure.
How do issues with colour constancy become apparent?
With LED lights, there are two different types of colour constancy problems:
a single LED strip segment or reel with a colour mismatch
between two or more LED strip segments or reels, there is a colour mismatch
You may detect the first discrepancy when the colour variance between individual LED bulbs inside a single LED strip is excessive. This often occurs as a result of the manufacturer's poor tolerance specification.
The second form of mismatch is more obvious and frequent when it comes to other lights. Usually, this happens as a result of variances across batches or manufacturers.
By utilizing LED lights from the same batch in a single installation, especially if they will be visible together, you may prevent the second type of inconsistency.
