What is CRI
CRI stands for Colour Rendering Index. In simple terms, it refers to the accuracy of colours that are visible when using a particular light. Ever wondered why your outfit, which seemed to glow in the store and looks great outdoors, takes on a dull appearance when worn in the office? CRI is the key to it all. Understanding the various use cases of different CRI levels is crucial to making the most out of your space, whether lighting a home, an office, a shop or a restaurant.
CRI is represented by an Ra rating i.e. 100Ra or 70Ra. The Sun produces light with a value of 100Ra, while those dim yellow street lamps on suburban streets dip down into the negatives, around -44Ra. When it comes to most residential or commercial lighting projects, you’ll be looking at ratings from around 70-100. 100Ra means that colours are true to life, that the complete visual light spectrum is being produced. When coming from the sun, this is known as natural light.
One thing to keep in mind is the difference between CRI and Kelvin. Kelvin is a temperature range and is used as a reference point for what colour of light an incandescent bulb would produce at a particular temperature. LED and Fluorescent lights do not rely on heat to create light, and so their Kelvin numbers are estimated based on what temperature an incandescent bulb would require to reach the same colour. A light with a temperature of 5000K will have a colour comparable to daylight, but this does not necessarily mean it will have a similar CRI, as the numbers are independent.
Pros and cons of older style bulbs
Only two kinds of bulbs available for home use offer a CRI rating of 100. These are incandescent and halogen bulbs. By heating up a filament of metal until it begins to glow, these bulbs produce light in essentially the same way as the sun does, i.e. through heat. While being great for showing accurate colours, this method of producing light is also what prevents these bulbs for being the most suitable option in most spaces.
These bulbs are very inefficient, with most of their energy usage going towards creating heat instead of light. As a result, high wattage incandescent bulbs have been gradually phased out in the recent past. Low wattage incandescent bulbs, such as our collection of 25W Edison bulbs, are a great option for high CRI decorative or mood lighting.
Halogen bulbs, while somewhat more efficient than incandescent bulbs, have their own issues, primarily excess heat. These bulbs still use a lot more energy than even higher-watt LED lights, but are common in appliances like ovens, where the ability to withstand high temperatures is paramount.
The types of bulbs available:
For general use lighting there are two other options available, fluorescent and LED lights. Each type has its own strengths, as we’ll explain below.
Commonly seen in places like offices and school corridors, fluorescent lights don’t always have the best reputation. The reason these lights have ended up in such spaces, however, owes to their best qualities – cost and efficiency! These tube shaped lights were a major step towards minimizing the environmental impact of lighting, providing a lot of light for less energy. Unfortunately, the light they produced was very low on the CRI scale, giving everything a distinctive cold and washed out look. While modern breakthroughs in fluorescent lighting now allow these lights to reach higher CRI ratings, it can be hard to distinguish between these as labelling can be inconsistent. Additionally, fluorescent lights use more energy than LED bulbs and are therefore less efficient.
The newest, most energy efficient and most versatile lighting technology – LED bulbs combine the best features of other bulb types. They are available in a range of high CRI options, typically from around 80 to 90Ra. LED bulbs at this level produce light that is vibrant and accurate, while using only a fraction of the energy required by either an incandescent or fluorescent bulb. Combined with their availability in almost every size and base type, LED bulbs are the ideal choice for almost any application, including situations requiring high CRI levels.
Recent advances in LED technology mean these bulbs can now mimic the look and styling of incandescent bulbs, giving you the best of both worlds with classic styling and energy efficiency in one.
Benefits of a high CRI value
High CRI lighting has numerous benefits over lower options. Colour accuracy affects how things look. As a result, any situation where colour is of importance will be improved by a higher CRI value. As an example, we mentioned clothing at the start of this article. In low CRI levels, similar colours blend together into one thing, meaning certain articles of clothing which may appear to match indoors might appear to be totally different shades and hues when taken out into the sun. Similarly, when decorating your home, you may find things like sheets and curtains, which looked vibrant and matching in the store, suddenly appear dull and may no longer match when brought into your home.
High CRI lighting in your home will ensure your decoration and style will appear as vibrant and lively as possible.
This is equally important in commercial spaces. A clothing retailer wants to ensure that their items are attractive and draw the eye, while a restaurant wants their dishes to appear fresh, delicious, and photo-worthy. Photography is an area which needs specific attention paid towards CRI as different levels can drastically change how the resulting photo appears. Because the CRI value is measured on the actual colours that are produced by the light, a low CRI value will result in dull photos.
Colour Rendering Index vs Colour Temperature
Whether lighting a cool bar or restaurant, or simply creating a cosy atmosphere in your home, mood lighting brings on a whole different feeling to a space than typical, bright lighting.
CRI requirements, however, are not one of the differences.
Much like with the colour temperature i.e. Kelvin, brightness has nothing to do with CRI levels. The colour rendering has to do with the colour spectrum of light, with the more full the spectrum, the higher the accuracy of the colours. Thus, a high CRI in low lighting will provide better light than a low CRI in low lighting, for all the same reasons as in bright lighting.