High CRI desk lamp: why does the color rendering index matter in choosing the best desk lamp for your home office?

If you have noticed that things look different in a store with fluorescent lights compared to a store with incandescent or halogen lights you are on the right track. Diamond stores use specific lighting to make their jewels and watches look glamorous, while old Kmart stores used inexpensive fluorescent lighting that made everything look a little green.

When LED lights first came out many made a room look "bright" but might also look a little "washed out." This is why CRI or colour rendering index is the second most crucial element in selecting a perfect desk lamp. This index is a simple and helpful lighting spec to predict how correct the visual output of a lighting product will be. The metric is a number between 0 and 100 used to predict how well a product renders color. The closer to 100, the better or more accurate colours should look under its light.

The CRI value of a light source indicates its ability to make colours look natural. Low values cause unnatural tints and hues to appear, while high values more accurately reflect the colour you're trying to produce. It's essential not just for how each colour looks but how it makes people look when they stand under the light source.

Our eyes have incredible colour sensitivity, which is why we have camouflage military uniforms and why our ancestors could spot a lion hiding in the grass early enough to escape. In nature, your eyes see colour reflected from objects. For example, a ripe strawberry reflects the red wavelength of light but not blue. However, if you look at it under an LED light that doesn't have a full spectrum of red light, the strawberry may look sickly or pink even if it is a perfect specimen.

The higher the CRI number, the better. A CRI of 80 and over is considered good, and a 90 plus rating is considered excellent. CRI numbers on a light fixture or bulb are like how well you studied for an exam: 80s are Bs, 90s are As.

CRI isn't related to color temperature. These two things are different, and we can use an example to prove it. For instance, a 5000K daylight-like fluorescent light could have low CRI of 75, but another one could have high CRI at 90.

For lighting companies to enable consumers to differentiate between high quality light and cheap ones that wash out colours, CRI is a useful indicator. Because the light coming from the sun reflects all the colours we can see, it has a CRI of 100. Today, by mixing and arranging different colours of LEDs, a good desk lamp can achieve over 90% of all colours found in sunlight.

To avoid buying a "bright" desk lamp that makes everything look pale and washed out you want to look for a desk lamp with a CRI of 90 or above. However, there are lighting products that are very bright, yet score low on the CRI due to poor colour handling. You want a product that combines both high brightness and colour accuracy. 

You need a high CRI rating for your desk lamp as it’s essential when working with detailed graphics design, while maintaining great home office lighting, and when long term eye care is a priority. In other words, for everyone who requires a monitor to do their work. 

If you do any work with pictures, advertisements, or graphics, you need a 90+ CRI lamp. Red light is essential in rendering natural skin tones, especially in hair colour or cosmetics. Flesh tones in computer-generated and printed images are susceptible to CRI fluctuations and look completely different under two different desk lamps.

If you worked on ensuring that your office is colour coordinated, or if you have visitors to your working area, you want a 90+ CRI light. For example, if you're going to make that cherry wood fancy executive desk look great, match it up with a desk lamp with 90+ CRI, and you will see every line and colour variation in your work surface. Match it with a low CRI $20 desk lamp, and the same desk may just look like something from a thrift store. 

Another benefit of 90+ CRI desk lamps is that they also come with additional advanced features, such as a flicker-free driver that eliminates annoying LED flickering and automatically adjustable light levels that keep the lamp from getting too bright when the room gets darker, such as at dusk. BenQ ScreenBar and e-Reading lamp have these advanced features and avoid monitor glare. Find out more in this review. 

If you are looking at desk lamps for your home or work office space, check out the BenQ ScreenBar Plus desk lamp with its innovative design that rests above your monitor and has a CRI of 95. For a more traditional desk lamp design, the BenQ e-Reading lamp is one of the fastest-growing desk lamps in North America. With its innovative head that keeps light off the monitor and on your desk, it covers over 30% more space than a typical desk light and has a CRI of 95. Here’s more info if you’re interested. 

To test CRI, we can setup several colour patches with precisely known colors. We then use a spectrophotometer to measure the colour of these patches under a light source. This process allows us to measure the colour of the light reflected from it.

Luminous output, measured in lumens, describes the brightness of a light source. CRI uses natural daylight in its calculation. A higher CRI indicates that the light spectrum resembles natural sunlight, while a lower score is more like or halogen/incandescent light sources.

We must remember that light sources with a colour rendering index below 70 alter our color perception. Light sources in this category include fluorescent tubes, also known as industrial white tubes.

Around 450 lux with a 6W to 9W LED bulb is excellent all-round brightness.