Colour Temperature: is a measurement in Degrees Kelvin (k) that indicates the hue of specific light source. Colour
temperature also sometimes known as CCT (correlated colour temperature) is usually presented on a Kelvin scale chart (see below).
As you can see Warm (yellow) light is represented with a smaller Kelvin
number than Cool (blue) light which is in turn respresented with a
higher Kelvin number. In the image below you can see the correlation between Colour Temperature and how the corresponding light source looks like.
Common LED Colour Temperatures: variations of these visible hues are normally described as Warm White (WW), Natural White (NW) & Cool White (CW). The Kelvin ranges that these fall into vary; however our chart above is a good indication, you can see on the right we have highlighted in Blue the Colour Temperature range for WW, NW & CW.
Which LED Colour Temperature Suites What Application: the most popular LED Colour Temperature is Warm White, this can be explained by the fact most people are so used to Incandescent and Halogen lighting that when it comes time to replace them with LED lighting they usually prefer the same colour temperature.
It is important to note how different colour temperatures affect your sourroundings, for example the general concensus is that Warmer light will project a more relaxed environment which is good for Living Spaces such as the lounge room or cinema room. While a Cooler light will create a more work focused environment which is good for Work Spaces such as the study, office or kitchen. In reality though, colour temperature is a personal choice, and we've seen customers after choosing Warm White try something Cooler with their next purchase and actually prefer it over WW.
The below image will give you a good idea of how a particular colour temperature will look like in an indoor interior.
CRI Index & Light Quality: CRI or Ra stands for Colour Rendering Index, it is a measure of how accurately a particular light source is able to render an object to its natural colour, ie. being able to make a "Tomato" look like a "Tomato". The index is a number from 1 to 100, with 100 being the most accurate representation of an object which in turn would mean it has the highest light quality. The rule of thumb is that anything over 70 is good, all our LED products have a minimum CRI of 70 with some over 80. Having said that, light quality is very subjective, although it is important that you dont go below a CRI of 70, the difference between say a CRI of 70 & 75 is hard to gauge. To put things in persepective, an Incandescent bulb is said to have a CRI index of 100, meaning it should "theoretically" have the best light quality, but do all people find Incandescent light appealing? Probably NOT? One thing a CRI index is good for is gauging the quality of the actual product itself, most cheap lights wont even list the CRI so stay away from those.
Lumen Maintenance: Compares the brightness of a light source when it is new to the amount of light output at a specific time in the future, this figure is then normally expressed in a table with one axis as the brightness as a percentage normalized to 100% @ 0 hours and the other axis a time scale usually in hours (see table below). One thing many of you will have notice by now is the very long "rated" lifespan of LED's, most of the LED Lighting we sell have a rated lifespan of over 50,000hours. How do we or the manufacturer's make such a claim you ask? To answer this, one must understand that LED's do not fail catastrophically like conventional lighting, instead as time goes on the LED diodes emit less and less light. In fact it is highly likely that the LED's we sell will last longer than 50,000 hours. So in calculating the lifespan of an LED, most manufacturers have adopted a 70% "lumen maintenance" cut-off, meaning by 50,000 hours or whatever the rated lifespan of the LED is, the light output should be 70% of the maximum Lumen output when the product was new. As you can see, the beauty of a good quality LED is that even at the end of the rated lifespan you will have a luminaire that is still shining pretty brightly. It has been scientifically proven that the human eye will begin to notice a difference when the light output has decreased to approximately 70% of its maximum, hence they have stuck to this figure.
In the lighting industry, the IES-LM80 is the test standard that describes how lumen maintenance testing should be conducted, and is normally represented in a table like the one below.