Warm Light Versus Cool Light: What Colour Temperature Means

Light isn't just bright or dim. It also has a colour, from candle-like yellow to bluish white. This is called colour temperature, measured in kelvins (K).

The scale

Kelvin	Look	Example
about 2,000–2,700 K	warm, yellow-orange	candle, cosy lamps
about 3,000 K	soft warm white	many home bulbs
about 4,000 K	neutral white	offices, kitchens
5,000–6,500 K	cool, bluish white	daylight-style bulbs, many torches

Higher numbers mean cooler, bluer light. The names sound backwards, since "warm" is the lower number.

How each feels

• Warm light feels relaxed, and is good for evenings.
• Cool light feels crisp and alert, and is good for tasks that need attention to detail.

Which suits what?

Task	Better light
Relaxing at home	warm
Reading a label	neutral to cool
Checking a map or a car engine	cool white
Searching outdoors	cool white, which contrasts well
Winding down before bed	warm

Torches and phones

Most phone flashes and torches give cool or neutral white light. That suits practical tasks, but it can feel harsh in a dim room. If you want to soften the light, you can cover the LED with a cloth or bounce it off a wall or ceiling.

Colour rendering

Colour temperature is different from colour rendering: how accurately a light shows real colours. Good rendering makes a red apple look red. Cheap LEDs can sometimes make colours look slightly off.

Bounce for comfort

In a dark room, pointing the torch at the ceiling gives a soft, wide glow rather than a harsh beam. This can be easier on the eyes and lights the whole space.

Practical tip

Use the torch briefly and directly when you need clear detail, and bounce it when you need general light. A quick-launch app makes it easy to switch on and off as the task changes.

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