When it comes to lighting, the warmth or coolness of a light source is referred to as its correlated color temperature (CCT). The CCT indicates the tone of the light on a scale from warm (reddish yellow) to cool (bluish white). Warm light has lower CCT values, typically below 3,300K, while cool light has higher values above 3,300K.
But which light is actually the warmest according to the CCT scale? Let’s take a look at some common light sources and their correlated color temperatures:
Incandescent Light Bulbs
Incandescent light bulbs produce light by heating a tungsten filament. This results in a warm, yellowish or reddish light. Incandescent bulbs have some of the lowest CCT values, ranging from about 2,700K to 3,000K.
Halogen Light Bulbs
Halogen bulbs are a type of incandescent that use halogen gas instead of inert gas. They produce a brighter, whiter light than regular incandescents. However, halogens are still considered a warm light source, with CCT values between 2,900K and 3,200K.
Compact Fluorescent Light Bulbs (CFLs)
CFL bulbs produce light differently than incandescents, using mercury vapor instead of a heated filament. The light is less yellow and more neutral in tone. CFLs have CCT values ranging from 2,700K to 6,500K, covering both warm and cool light.
Warm White LED Light Bulbs
LED bulbs are highly energy efficient and long-lasting. Warm white LEDs mimic the look of incandescent or halogen lighting, at lower wattages. They come in CCT values of 2,700K to 3,000K.
Soft White LED Light Bulbs
Soft white LEDs are a step above warm white, producing a more natural, less obviously yellowish tone. Their CCT range is from 3,000K to 4,000K. This makes them a popular choice for general everyday lighting.
Cool White LED Light Bulbs
Cool white LEDs produce a crisp, bluish-white light. With CCT values from 3,500K to 5,000K, they are considered cool but not extremely stark or blue. They work well for task lighting.
Daylight LED Light Bulbs
Daylight LEDs replicate natural outdoor light, with a blueish tone similar to sunlight. They range from 5,000K to 6,500K on the CCT scale. This makes them the coolest LED option, closest to actual daylight.
High CCT LED Light Bulbs
Some LED bulbs go beyond daylight, offering very high CCT values above 5,000K. This produces an extremely cool, blue-tinged light. High CCT LEDs are used more for commercial settings than in homes.
Fluorescent Tubes & Strip Lights
Fluorescent tubes and strip lights come in both warm and cool CCT ratings, depending on the specific product. Warm fluorescents range from 2,700K to 3,500K, while cool fluorescents are above 3,500K.
Smart Light Bulbs
Smart bulbs like Philips Hue can produce millions of colors, and also different whites at various CCTs. For example, the Philips Hue white ambiance range offers warm to cool CCT settings from 2,200K to 6,500K.
Candle Light
The warm flicker of a candle has the lowest CCT of any light source. Natural candlelight registers at only about 1,850K on the scale. This makes it the warmest form of indoor illumination.
Comparison of CCT Values
Here is a table summarizing the typical CCT ranges for common light sources:
| Light Source | CCT Range |
|---|---|
| Incandescent bulbs | 2700K – 3000K |
| Halogen bulbs | 2900K – 3200K |
| CFL bulbs | 2700K – 6500K (warm to cool) |
| Warm white LED bulbs | 2700K – 3000K |
| Soft white LED bulbs | 3000K – 4000K |
| Cool white LED bulbs | 3500K – 5000K |
| Daylight LED bulbs | 5000K – 6500K |
| High CCT LED bulbs | Over 5000K |
| Warm fluorescent tubes/strip lights | 2700K – 3500K |
| Cool fluorescent tubes/strip lights | Over 3500K |
| Smart bulbs (variable CCT) | 2200K – 6500K |
| Candlelight | About 1850K |
Warmest Light Sources
Based on typical CCT ratings, the warmest types of indoor light are:
- Candlelight (about 1850K)
- Incandescent bulbs (2700K-3000K)
- Halogen bulbs (2900K-3200K)
- Warm white LED bulbs (2700K-3000K)
- Warm CFL bulbs (2700K-3500K)
candlelight produces illumination closest to an amber red-yellow tone. The low CCT of 1850K is what makes candles the warmest man-made light source. Though incandescent and halogen bulbs come close, with ratings in the 2700K to 3200K range.
LED and CFL bulbs can also produce warm light below 3500K, competing with incandescents. However, at the lowest end, they still don’t reach the coziness of a candle flame.
Why Light Warmth Matters
The warmth or coolness of light affects the ambiance, as well as visual appearance of objects. Warm light tends to create a more inviting, cozy feeling. It enhances warm material colors like wood, gold, red or skin tones. Cooler light is more energizing. It can make spaces seem cleaner and make colors appear brighter. However, it can also create a harsher, less welcoming mood.
For living areas like bedrooms and lounges, warm light around 2700-3000K is generally preferred. Kitchens and workspaces benefit from slightly cooler light from 3500-4000K for tasks. Outdoor spaces, bathrooms or garages can use cooler light up to 5000K or higher.
With tunable smart bulbs, you can change color temperature to suit different needs. Setting them to warm white in the evenings and cool white in the daytime allows you to match the natural circadian rhythm.
Factors Affecting Perceived Warmth
While CCT (correlated color temperature) indicates the actual warmth of light, other factors also impact how we perceive it:
- Brightness – Lower brightness makes a light seem warmer. When a cool light is dimmed it will appear warmer.
- Size of light source – Small point sources like candles or mini lights appear warmer.
- Color rendering – Good CRI (color rendering index) enhances warm tones.
- Surrounding colors – Warm light will stand out more against cool blue tones in a room.
So CCT alone doesn’t tell the whole story of how we experience the warmth or coolness of illumination. But it remains a useful standardized specification for comparing different light bulbs or fixtures.
Choosing Light Bulbs
Here are some tips for choosing light bulbs based on CCT values:
- For general living areas, pick warm white bulbs in the 2700K-3000K range for a cozy ambiance.
- Soft white bulbs (3000K-4000K) are suitable for kitchens, bathrooms and work spaces.
- Daylight bulbs (5000K-6500K) are good for high activity areas like garages and attics.
- Go for highest rated CRI (80+) for best color rendering.
- Try mix and match – warmer bulbs for ambiance, cooler for tasks.
- Use smart bulbs to adjust CCT automatically or on demand.
Conclusion
When evaluating the warmth of light, candlelight comes in at the top with a CCT of 1850K. Incandescent and halogen bulbs come in second, offering that traditional warm glow. For energy efficiency with excellent color, warm white LEDs are a great choice. The right light warmth contributes tremendously to an enjoyable, inviting environment.
