4 Most Important Light Source Parameters You Should Know

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Have you ever read all the important light source parameters and thought ‘What the heck is this’? I know I did… But then I realized all this information could actually be very helpful not only for technicians but for us, interior designers as well. It gives you a lot of information on the lamp you’re about to use and thus making the choice of the perfect fixture much easier.

Let’s dive in and try to decipher those abbreviations, shall we?

1 | IP - Ingress Protection

This parameter describes the effectiveness of the sealing of a given light fixture. It consists of two digits, the first one regarding the level of protection against foreign bodies (dust, dirt, tools, etc.) and the second - protection against moisture.

Thanks to this parameter you can choose the appropriate light fixture depending on its placement. It’s crucial for wet spaces, like bathrooms, and for the outdoors, where the protection level has to be high.

*TIP - I’m sure you’ve noticed the trend of hanging a pendant lamp above a bathtub, right? Now, be careful if you’d like to do that in one of your projects. The light fixture placed in such proximity to a water source (and in a humid place) should have an IP rating of at least 44. However, most of the pendants on the market today, have an IP of 20. This can be dangerous, so make sure to pay attention to the IP rating of the light fixtures you choose.

Ingress protection is super important when choosing the light source

2 | CRI - Color rendering index

This one of the important light source parameters is used mostly with LED lamps, even though it regards every artificial light source there is. CRI is the measurement of how well a given light source renders the colors of the objects it illuminates. It is compared to the color rendition of sunlight, which, as you can tell, is the perfect rendition. Therefore, the highest CRI value is 100. Other light sources that have CRI 100 are halogen and incandescent light sources (classic light bulbs).

LED lights, however, very rarely reach CRI 100. Most of the ones we use in residential spaces vary between CRI 70 to CRI 90. You can also find professional LED light sources with CRI 95 (those are getting more and more available also for residential interior design).

*TIP - I recommend using LED light sources with CRI no lower than 90 unless you place it in a spot where color rendition is irrelevant (shed, technical room, etc.). If a lamp doesn’t have information about CRI, it’s probably very low.

CRI is one of the most important light source parameters you should know

3 | CCT or CT - Color correlated temperature or color temperature

If you’ve never heard this term, you might be surprised. But yes, there is something like color temperature (measured in Kelvins). It’s the hue of the light emitted from a light source, depending on its power. You probably noticed that some lamps emit a warm, yellowish light, while others - are white and fresh. These are the various color temperatures. 

Now the funny thing is, that the whole color temperature grading is kind of counterintuitive. We normally correlate high temperatures with warmer colors, like yellow or red, and low temperatures with white and blue, however here it’s actually the contrary. The higher the power of the light source and therefore the higher the temperature - the color gets bluer, and colder in hue. And the lower the power and the temperature - the color gets redder, so warmer in hue. 

The most common color temperature of light sources to use in residential spaces is anything from 2700 K to 4000 K. 2700 K is a warm, yellowish light, suited mostly in bedrooms because of its relaxing features, and 4000 K is a neutral white color, perfect for kitchens or offices.

*TIP - be mindful of the color temperature you use for various spaces. The hue of the light emitted from the light source might impact the colors of materials used in a room. It also impacts our mood and productivity. It's probably one of the most important light source parameters you should know.

various color temperatures based on the power of a light source

4 | UGR - Unified Glare Rating

This parameter measures the glare caused by a light fixture on a given surface. And as much as it’s super important when designing public or office spaces, it can also be interesting to be considered for residential spaces. Why? Because the stronger the light source we use, the higher the risk of it causing glare. Especially when placed too low or too close to a reflective surface.

Imagine a strong halogen lamp placed too close to a white desk with a satin finish. I can already feel the discomfort and strain in my eyes from the glare caused by the reflected light. To avoid that, you can either put the light higher/further from the surface or use a lamp with a low UGR.

UGR value ranges from 10 to 31, 10 meaning no perceived discomfort, and 31 indicating intolerable discomfort. So it’s obvious that the lower the UGR rating, the better. However, since the manufacturers cannot predict the exact conditions in which their product will be used, they usually express the UGR parameter with the “≤” sign, which indicates the highest possible value.

Learn more!

These are obviously not the only parameters or characteristics of a light source you should know. But they definitely can come in handy when choosing a light fixture for your project.

If you’d like to learn more about light, what it is, and how to use it in your projects - make sure to get a copy of my ebook titled “Everything an Interior Designer Should Know About Light" that’s just come out! 

hi there!

I'm Aleksandra, an interior architect with multinational experience, on a mission to help beginning or self-taught designers gain confidence and create systems that will help them bring their businesses to the next level.




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hi, I'm Aleksandra!

I will help you create an organized interior design business with systems and processes, and to gain confidence to bring your career to the next level.

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