Lighting Part 1: Lighting Characteristics

Welcome to part 1 of our multipart series! Ever look at the side of a light bulb’s box and find all the numbers confusing? In today’s post, I’ll start with the nerdy basics and break down the physical properties of a light. Some of this will be fairly intuitive while other concepts you may not have thought much about.

Intensity

Short answer: This is a fairly straight forward concept - how “bright” a light is. What’s not straightforward are the units used to measure this (candelas, lumens, and lux). Lumens represent the total amount of light from a source where candelas represent how concentrated a beam is. Both of these are independent of distance. Recall that a light source will appear dimmer as it is moved away from you. Lux takes this into account and is a measure of how much light is actually getting to a given surface. Watts are a measure of how much power a light consumes and should not be used as an indicator of light brightness, as various lighting technologies have different efficiencies. Bottom line, use lumens to compare total amount of light produced, candelas for comparing directional lights like flash lights, and avoid using watts as an indicator of brightness. Still confused? See my long answer here.COLOUR TEMPERATUREShort answer: “White” lights can differ in actual color despite all of them looking white to the viewer. They can be amber, they can be blue, or they can fall anywhere in between. One may only notice these differences when two lights of different colour temperature are right next to each other, allowing for direct comparison (e.g. car headlights in the daytime looking amber compared to sunlight which looks white). Typically amber incandescent lighting (AKA “warm white”) is measured at ~3200 kelvins (K) while more bluish daylight (AKA “cool white” or “daylight”) is measured at ~5600 K. Want more detail? See my longer explanation here.

Notice how the under cabinet lights appear amber when viewed next to the sunlight from the window.

At night, when the under cabinet lights are viewed by themselves, they appear white.

Colour rendition index

Short answer: Colour rendition index (CRI) is another concept that many people have never given much thought to. This refers to how “full” the colour spectrum of a white light is (when broken down by a prism) and in turn represents how well it will render the colours of the object it is illuminating. The highest rating on the scale is 100 (incandescent bulbs and sun). While colour temperature refers to the colour of the light, CRI refers to the quality of the light. Still not making sense? See my longer explanation here.

Light softness

Short answer: The final characteristic of light one needs to consider is how “soft” the light is. This is talked about a lot in photography/film, but I haven’t come across it much in renovation/lighting design resources. I have included it here because the same principles apply for lighting a space. How soft a light is refers to how well it can evenly illuminate an object and how smooth the shadows are. It depends on the effective size of the light source (bigger and closer = softer) and therefore may be dictated more by the type of light fixture used. Soft lights produce smooth (and sometimes nonexistent) shadows, while hard light sources produce harsh, well defined shadows. Depending on the usage, you may prefer one style of light over the other. Like reading me ramble on? See my longer explanation here.

Generally, hard direct light is more dramatic than soft shadowless light.

That’s all for today’s post. Stay tuned for part 2, which will cover the various lighting technologies available!