How colour-tunable (CCT) lamps work

Colour-tunable lamps give you both warm and cool light from one fitting. What happens inside them and what to check when choosing one.

Crisp, neutral light in the kitchen in the morning and soft warm light from the same fitting in the evening: a few years ago this required two different lamps. Today colour-tunable lamps, CCT lamps for short, do it in a single body. In shops you will see them sold as “tunable white”, “CCT” or “colour-changing white”. To choose well, it helps to know how they work.

What CCT means

CCT (Correlated Colour Temperature) expresses the tint of white light in kelvin. A “CCT tunable” lamp can change that tint within a set range, for example from warm 2700K to cool 6500K. There is an important distinction here: this is about the tone of white light, not coloured light such as red, green or blue. RGB lamps that produce coloured light are a separate group, although some models combine both functions.

What happens inside: two channels

Most CCT lamps contain two groups of white LEDs: one gives warm light (say 2700K), the other cool light (say 6500K). The lamp's electronic driver controls the brightness of each group separately.

• With only the warm group on, the lamp gives its warmest tone.
• With only the cool group on, it gives its coolest tone.
• With both on in a given ratio, the light mixes into an in-between tone, such as 4000K.

Brightness is usually controlled by very fast switching (PWM) or by varying the current. With a good driver this process is invisible to the eye and the camera; with a poor one, flicker can appear.

Quality at in-between settings

Mixing two different whites seems simple, but there are subtleties. A mix of warm and cool light does not always fall exactly on the “ideal” white light line; at in-between settings the light can take on a slight pinkish or greenish tint. In good lamps this is barely visible; in cheap models it can be noticeable.

In addition, on some models the total amount of light changes with colour: at the extremes only one channel is working, so the lamp can look dimmer than in the middle. Colour rendering can also differ between channels. If the technical description gives this information, it is worth checking.

Control methods

There are several ways to change the colour of a CCT lamp:

• with the wall switch: switching off and on again quickly moves the lamp through preset modes (for example warm → neutral → cool); no extra wiring is needed, though “hunting” for the mode can be annoying;
• with a remote: a slider or buttons let you pick any tone;
• with a phone app or smart home system: you can set schedules and scenes;
• in professional installations, with dedicated control protocols that manage every fitting in a building centrally.

When choosing, make sure all the lamps in a room are controlled the same way and at the same time. Lamps paired with different remotes can easily end up in different modes.

Dimmer compatibility

CCT lamps on ordinary wall dimmers do not always behave as expected. Models that change mode via the switch may not work properly with a dimmer, because the dimmer also “chops” the voltage and the lamp can read that as a mode change. If you plan to use a dimmer, the box should state both “dimmable” and compatibility with the type of dimmer you use.

There is also a separate technology called “dim-to-warm”: there the colour is not controlled independently; the light simply gets warmer automatically as it dims. That is not the same as CCT tuning.

Where it genuinely helps

The advantage of CCT lamps shows where one space has different needs:

• a kitchen-living room: work by day, relaxation in the evening;
• a child's room: neutral for homework, warm before bed;
• a home office: alertness in the morning, comfort in the evening;
• hotel rooms and restaurants: atmosphere that follows the time of day.

In single-purpose places such as a hallway, a storeroom or a bedroom used only in the evening, an ordinary fixed-colour lamp is simpler and often more economical.

Before choosing a lamp, find answers to these questions:

• What is the colour range: 2700–6500K or narrower?
• How is it controlled: switch, remote, app?
• Can it be used with a dimmer, and which type?
• Is there information on light output and CRI at in-between settings?
• Are all lamps in one zone the same model?

Whether a particular Zəfər İşığı model can change its colour tone, and how, is a question best put to Zaferoğlu Elektrik via its website enquiry form.