UNDERSTANDING COLOUR TEMPERATURE IN LED LIGHTING
When selecting LED lighting, or any lighting for that matter, getting the colour temperature right is of paramount importance. Is seems that not a day goes by that I don't see a news report with someone complaining about annoying blue LED light streaming in their windows at night or that they wish they could get that warm feeling that they used to have from an Edison style bulb back again.
This is an understandable sentiment as most early LED lighting glowed with a white light which feels unnatural to humans. People are used to the light colour that we receive from the sun or a fire. This is the reason why fluorescent lighting derived from a chemical reaction feels unnatural too. The range of light colours emitted from sources like the sun is measured in degrees Kelvin on the colour temperature scale.
Traditional incandescent bulbs emit light on the colour temperature scale naturally and thus the light is generally seen as quite relaxing and pleasant. Fluorescent lighting, on the other hand, emits light on its own scale and thus has to be correlated with the traditional colour temperature scale such that we give it a Correlated Colour Temperature (CCT) to represent the colour of its light. LEDs are the most flexible light source and, with expert tuning, can emit just about any colour including those on the traditional colour temperature scale.
Because LED lighting is available in a wide range of colour temperatures, it is important that buyers select an appropriate CCT for their purpose. I generally think of colour temperature in terms of what light people would naturally use at different times of the day. Lower colour temperatures such as 1500-2000K are what we would expect from a naked flame and 2400K is typical of a traditional incandescent bulb. In the higher temperatures 4000K is roughly what we see in the moonlight and 5900K is the colour of the sun before it enters our atmosphere and gets distorted into a much wider range.
For my office environment I prefer 5000K LED bulbs so that when the sunlight streams in the window during the day, there is no noticeable difference in colour temperature as I move around the office. In the pictures, you can see the difference between no lights on, 5000K and 2700K lights with the 2700K lights casting a dingy looking orange light around the workspace.
Once the sun goes down, things are a bit different. In the pictures below I have just closed the curtains, but the affect is similar to a night time scenario. You can see how much more cosy the room feels with the 2700K bulbs plugged in. Almost like a grand office from yesteryear. With the 5000K bulbs plugged in, the office looks more clinical and not nearly as inviting. Since I use the office mostly during the day, 5000K suits me fine. If I was using it day and night, I would probably look at something closer to 4000K lighting to make it a little friendly in the evenings, but still easy to concentrate during the day. I would probably only recommend 2700K for an office if you only used it during the night for more recreational study pursuits.
As a basic recommendation, I would say that anywhere where you are often blending light from outside, a 4000-5000K light is going to be your best bet. You really only want to go above 5000K for places like hospitals or design studios. I use 4000K spotlights in the kitchen where seeing what I am doing and judging colour is important. They are not as high as in the office because I am often in there at dusk when the colour temperature outside is dropping but I still want a clear light to work by. In the living room and bedrooms the lights are all below 3000K to create atmosphere and a warm cozy feeling at night.
If you have a space that you are trying to decide on a colour temperature for, leave a comment below and we will help you out.