Become an expert on light

It doesn't matter if your luminaire is made of wood or steel, fabric or aluminium, copper or brass. The light source is by far the most important part for the lamp to be experienced in the right way at home. Without the right colour temperature and colour rendering, that fixture won't be the amazing piece of interior design that you wanted; instead of enhancing your home, it can ruin the whole experience.

Oscar Nyström, one of the world's leading lighting designers, currently working at his own start-up Art of Light, helps hotels, restaurants, museums and private individuals all over the world with lighting design. Grand Hotel Stockholms Vinterträgård, the exclusive Grand Hotel Chateau de Versailles, Royal Manssour, La Mamounia in Morocco are examples of some of those who have received help with lighting design from Oscar and Art of Light.

- Choosing the right light source is more complex than it first appears. Since the advent of LEDs, it has become even more complicated. And guidance is hard to find. My advice is to learn the basics yourself, in order to make an informed consumer decision. Most lamp retailers today simply don't have enough knowledge to help you.

So in this exclusive guide, we turn to Oscar for a deeper understanding of the many sources of light.

Understand the history of light sources

A few years ago, we switched from incandescent and halogen to LED, and with that, Swedish homes went from the warm inviting light we were so used to, to something much cooler. The warm glow of a standard incandescent bulb is 2700 Kelvin (which we will come back to). The LED lamp gave us the cold 3000-4000 Kelvin. Today, it's hard to tell the difference between the glow of a good LED and an incandescent bulb. And almost all light sources are and will be LED models.

Nevertheless, many people still have the old way of looking at the light source; you go to the store and buy a lamp by power in watts (W) and not in luminous flux lumens (lm). But this is too basic.

Choose LED

LED, or Light Emitting Diode, consists of small high-intensity LEDs instead of filaments. The advantage of filaments is that they become warmer when dimmed. But they also generate a lot of energy in the form of incandescent light and heat. And burn out quickly in 2000-3000 hours. An LED lamp lasts 30-50 000 hours, generates virtually no heat and consumes five times less power. And it now has the same feel as an incandescent or halogen lamp.

Forget Watt and focus on Lumen

In simple terms, Watt (W) stands for power, and measures the energy consumption of a light bulb. This concept does not translate to the LED lamp (a 7W LED can illuminate just as well as a 40W incandescent lamp). That's why Lumen (lm) is the current measure of brightness and the metric you should look at to find the right luminous flux for your luminaire. You could say that decorative lighting should have a fairly low lm, general lighting slightly higher and task lighting the highest.

Choose the right color temperature

Kelvin (k) measures the colour temperature and is an incredibly important value when lighting your home. Full Kelvin is 10,000K and corresponds to a clear blue sky, 6500K is daylight. A candle has about 1800K, so the lower the Kelvin value, the warmer the light. Always buy a lamp with a temperature below 3000 K. For a home, 2700 K is recommended.

And correct colour rendering

RA, or CRI - colour rendering index, stands for colour reproduction. Sunlight, candlelight and halogen light all have an RA value of 100, which means they provide 100% colour rendering; all colours appear true in their light. Most LED lights you find in stores today are at 85-90, which is fine. But it's best to find an LED lamp with an RA of 95-98.

Dim to warmer light

Dim-to-warm or warm-dim is perhaps the most important feature to focus on in today's LED lamp landscape. For hundreds of years, we humans have been used to incandescent light, which when dimmed automatically becomes warmer from 3000k-1800k. But that's not how ordinary LEDs work; if you dim a static example of 3000K colour temperature, the light will appear grey. Therefore, always buy a so-called retrofit LED lamp with Dim-to-warm or warm-dim effect. It behaves like an incandescent lamp and thus becomes warmer when dimmed.

Built-in light sources and Tunable White

Many lamps today have integrated light sources. When you can't control the characteristics of the light source yourself, it is particularly important to check the above-mentioned points before buying a new lamp. The really geeky ones ask for Tunable White. This is an integrated light source with a separate driver that allows you to easily control the brightness and colour temperature up and down the Kelvin scale, and get completely different impressions from the same light source.

Avoid mixing incandescent/halogen with LEDs

We often replace one light source at a time. Which means that in many homes there is a healthy mix of old incandescent bulbs, the occasional halogen and a few different versions of LED lights. This creates a cluttered look with varying strength, colour rendering and warmth.

Make sure to have at least the same type of light sources in the same room. And if you have a crystal chandelier or something else with many small lights, don't replace one without making sure it provides the same light as the others.

A short guide

Memorize so you always have the light source tool with you

• Always choose an LED lamp.

• Make sure it has the right Lumen, i.e. brightness for your luminaire and needs.

• Never colder than 3000 Kelvin.

• Always an RA value of at least 90.

• Buy a retrofit LED lamp that is dimmable and fits your dimmer, with the same characteristics as an incandescent or halogen lamp.

• Preferably invest in Dim-to-warm 3000 - 1800 Kelvin.

• Be careful with integrated light sources, where you cannot control the light.