What Blue Light Is and How Colour Temperature Affects It

Every LED bulb carries a colour temperature rating, but what that number actually tells you about the light in the room rarely gets spelled out. Warm white and cool white are the labels you'll see on packaging; what sits behind them is a spectrum, and the warmer end of that spectrum carries less blue light than the cooler end. This piece covers both what blue light is and how colour temperature determines how much of it a globe emits, along with actual figures independently tested across Dulora's full range, from the warmest dimmed setting, Sunset Dim, right through to 4000K natural white. Real numbers rather than a general impression.

The link between colour temperature and blue light

LED colour temperature is the headline spec on every bulb box, but it also predicts something most shoppers never see: how much blue light that bulb actually emits. Light is a spectrum, not a single quality. Every white light source, daylight, an LED bulb, a screen, is a mix of wavelengths across the visible range, and that mix determines both how warm or cool the light looks and how much of it falls into the blue band. Blue light sits at the shorter-wavelength end of the visible spectrum. It's a normal part of any white light source, not something LEDs introduced and not something limited to screens.

Colour temperature, measured in Kelvin, is the simplest way to predict how much blue light a source carries. A lower Kelvin number describes a warmer, more amber-leaning light; a higher number describes a cooler, bluer-leaning light. That's not a coincidence or a marketing framing; it's the same underlying property showing up as two different measurements. The colour temperature a globe is rated at and the proportion of blue wavelengths in its output move together: the lower the Kelvin rating, the lower the proportion of blue wavelengths tends to be, across every colour temperature Dulora has independently tested.

Where blue light comes from: a fair comparison

The visible spectrum runs from around 380 to 780 nanometres. Blue light sits at the shorter end, roughly 380 to 500 nanometres, and is present in almost every white light source, just in varying amounts.

The smartphone figure is worth a second look: its blue peak is proportionally strong, but at normal reading distance it puts out only 30 to 50 lux against 25,000 to 30,000 lux from midday sun, nowhere near the dose of a walk outside. More useful is the pattern across colour temperatures, which lines up closely with Dulora's own tested figures, from 4.4% at 4000K down to 0.6% to 0.7% on Sunset Dim dimmed to 1800K.

What the research says about blue light and sleep

What follows is what the published research says about blue light and sleep, attributed to specific studies, not medical advice, just what the evidence shows.

In 2001, Brainard et al., in the Journal of Neuroscience, and Thapan et al., in the Journal of Physiology, independently mapped melatonin suppression to a photoreceptor peaking around 460 to 480 nanometres, later identified as melanopsin-containing retinal ganglion cells: blue light specifically, not brightness, drives the circadian response.

West et al., in the Journal of Applied Physiology in 2011, found blue LED exposure suppresses melatonin in a dose-dependent, sigmoidal curve, more exposure meaning more suppression, up to a point, not a fixed effect regardless of intensity.

Phillips et al., in PNAS in 2019, found suppression exceeding 50% at around 30 lux, comparable to a dim living room, with a fifty-fold difference between individuals. Dain, in Ophthalmic and Physiological Optics in 2020, found blue light proportion tracks colour temperature, not technology, LEDs don't emit more than fluorescent or incandescent sources at a matched CCT.

The most useful benchmark is Terán et al., in Scientific Reports in 2026, which tested 52 lamps and calculated a Melatonin Suppression Value for each: cool white LEDs at a median 12.3%, warm white LEDs 3.6%, warm CFLs 2.6%, incandescent 1.5%, and tunable LEDs ranging from 10% at 5700K down to 0.1% at 2100K, the closest benchmark to Sunset Dim at 1800K.

Sanchez-Cano et al., in Life in 2025, measured melatonin over three hours: 26.0 pg/mL under warm light against 7.5 under blue light at the two-hour mark, narrowing to 16.6 against 8.3 by hour three, warm light staying clearly higher throughout.

Eighteen circadian researchers, including Brainard, Czeisler, Lockley, and Skene, recommended in PLOS Biology (2022) that evening light stay under 10 melanopic lux and the sleep environment under 1 melanopic lux, the field's closest thing to an agreed benchmark. Nagare et al., in Lighting Research & Technology in 2019, found adolescents showed 43% suppression under cool 5600K light against 29% under warm 2700K, a larger gap than adults showed.

No trial has directly compared 0% blue light to roughly 1%. Terán's 0.1% figure at 2100K, close to the range most Dulora products sit in, supports treating that difference as not clinically meaningful, while the gap between 1% and 12%, warm globe versus cool white LED, is substantial and well documented.

How Dulora's globes compare, with real data

Every figure here comes from independent testing, Everfine for the filament range, BlueRatio for Sunset Dim, not manufacturer estimates. Set against Terán's MSV benchmarks above, Dulora's range steps down gradually as colour temperature drops, though the two measures aren't equivalent, so the comparison below is directional.

Sunset Dim's lowest setting stands out: dimmed to around 1800K it measures 0.6% to 0.7% blue light, close to the 2100K tunable benchmark where Terán's team measured just 0.1% suppression, the lowest figure in that 52-lamp study, not a one-to-one match but the most relevant benchmark for what Sunset Dim does once dimmed for the evening. At full brightness it behaves like a standard 2700K globe.

Dedicated blue-light-blocking bulbs filter more aggressively than a standard warm LED. Dulora hasn't tested those independently, so no number is given here, the fuller comparison is further below. Dulora's figures come from shifting colour temperature, not filtering, which is why the lowest readings come with ultra-high colour accuracy attached, not instead of it.

Dulora's verified blue light figures, 1800K to 4000K

Every figure below comes from independent spectral testing, Everfine Corporation on Dulora's fixed-CCT filament globe range, BlueRatio on the Sunset Dim dim-to-warm spotlight range, not from internal estimates. Both testing regimes covered the full 380 to 780 nanometre range and measured the actual proportion of blue wavelengths for each product. The Product Type column matters here: the filament rows are separate products, each permanently fixed at that colour temperature, while the two Sunset Dim rows are the same physical spotlight measured at the two ends of its dimming range, not two different products.

The pattern is consistent, and once the numbers sit side by side it's fairly intuitive: blue light content roughly triples between 2000K and 4000K, climbing from 1.3% to 4.4% as colour temperature rises. 2700K vs 4000K is the clearest single comparison among the fixed-CCT products, blue light content nearly doubles, from roughly 2% to 4.4%, just by moving up the colour temperature scale. The 3000K figure, 2.1% to 2.7%, comes from two tested SKUs, an A60 and a G125, a third SKU tested at that colour temperature, a G95, doesn't have a published RGB breakdown, so it isn't reflected in this range. Sunset Dim's two rows sit at the very bottom and in the middle of that same scale, 0.6% to 0.7% dimmed, level with the 2700K filament globes at full brightness, because it's one spotlight covering both jobs rather than a separate product at each end.

Sunset Dim: the lowest blue light in Dulora's range

The summary table above already places Sunset Dim's two readings against the filament range, this section goes into the full per-SKU detail behind them. Independently tested by BlueRatio, Sunset Dim's GU10 and MR16 spotlights measure 0.6% to 0.7% blue light when dimmed to their lowest setting, around 1800K, the lowest figure anywhere in Dulora's current lineup and roughly half the 1.3% measured on the warmest filament globe above.

That figure is the low end of a working range, not a fixed rating. At full brightness, the GU10 spotlights measure around 1.7% to 1.8%, comparable to the 2700K filament globes, because full brightness on a dim-to-warm spotlight behaves like a standard 2700K light. That's the actual point of the dim-to-warm mechanism: one fitting covers both ends, a functional daytime reading and the lowest blue light figure in the range once it's dimmed for the evening. As Sunset Dim dims, lumen output and colour temperature shift together, which is why the light feels genuinely different at low brightness rather than simply darker. The GU10 36 degree spotlight's full-brightness reading isn't included in that range, its test came back at 3026K rather than its rated colour temperature, and that's being confirmed with the supplier before it's published. The table below also currently has a full-brightness reading for MR16 dimmed but not MR16 at full brightness, since the 2721K reading that was standing in for that row has moved to GU10, see the note below the table.

How this compares to dedicated blue light blocking bulbs

Dedicated blue light blocking bulbs exist as their own category, built to filter blue wavelengths more aggressively than a standard warm LED. We haven't independently tested any of those products, so we won't put a number next to them the way we can our own range, publishing a figure we haven't measured isn't something we're willing to do, whichever direction it would point.

What's worth understanding is the trade-off that kind of filtering generally involves. Stripping blue wavelengths out of a light source changes the rest of the spectrum too, and colours other than the extremes, skin tones and reds in particular, often render less accurately once part of the spectrum has been removed. Dulora's approach doesn't rely on selective filtering. The figures above come from working through colour temperature itself, shifting the whole spectrum warmer rather than carving a piece out of it, which is why Sunset Dim's 0.6% to 0.7% reading comes with ultra-high colour accuracy alongside it, not instead of it.

A practical guide to choosing by blue light priority

Ranking Dulora's own tested blue light bulbs from lowest to highest blue light content:

Lowest available: Sunset Dim dimmed to its 1800K setting, 0.6% to 0.7%. Suits bedrooms and living areas where the same fitting needs to shift from functional during the day to atmospheric in the evening. See the dim-to-warm range.

Very low: 2000K filament globes (fancy round, ST64), 1.3%. A fixed, always-warm option for spaces that don't need a daytime-to-evening shift.

Low: 2200K filament globes (A60, ST64), 1.4% to 1.5%. Close behind, with a slightly whiter cast than 2000K.

Moderate: 2700K filament globes, and Sunset Dim at full brightness, 2.0% to 2.5%. Standard warm white, suited to general everyday use.

Higher: 4000K filament globes, 4.4%. Natural white, suited to task areas where a crisper, daylight-adjacent tone matters more than a low blue light reading.

For anyone prioritising the lowest blue light figure specifically, Sunset Dim dimmed low and the 2000K filament range are Dulora's two lowest-measured options, and Sunset Dim carries the practical advantage of also working as a normal 2700K light during the day rather than being a single fixed setting. That's the warm white vs cool white LED comparison boiled down to a column of measured numbers rather than a feeling.

Frequently asked questions

What percentage of a Dulora globe's output is blue light?

It depends on the product and colour temperature. Across Dulora's independently tested range, it runs from 0.6% on Sunset Dim dimmed to 1800K up to 4.4% on a 4000K filament globe, with every colour temperature in between measured and published rather than estimated.

Does warm white vs cool white affect blue light content?

Yes. Across every Dulora product independently tested, lower colour temperature corresponds to lower blue light content. Warm white globes around 2000K to 2200K measure 1.3% to 1.5% blue light, while a 4000K natural white globe measures 4.4%.

Which Dulora product has the lowest blue light output?

Sunset Dim, dimmed to its lowest setting around 1800K, measures 0.6% to 0.7% blue light, the lowest figure independently verified anywhere in Dulora's current range.

Are Dulora's low blue light globes still colour accurate?

Yes. Every product across the range, including the lowest blue light options, is built to ultra-high colour accuracy. Dulora's approach works through colour temperature rather than selectively filtering wavelengths, which is why the low blue light figures don't come at the cost of colour rendering elsewhere in the spectrum.

Is warm white or cool white better for eyes?

We don't have eye-health outcome data to speak to that directly, so we're not going to claim one is better for your eyes than the other. What we can speak to is what we've actually measured: warm white runs lower for blue light content than cool white across every Dulora product tested, from 1.3% to 2.5% in the warm white range up to 4.4% at 4000K cool white. What that difference means for eyes specifically isn't something we'll claim either way without research to back it up.

The research above on light and melatonin describes what's been measured in controlled studies, not a promise about how any particular room, routine, or body will respond. Dulora's own figures are independently tested blue light percentages, nothing more, nothing less. For a closer look at how colour temperature and timing work together for sleep specifically, see Dulora's guide to circadian lighting for sleep.

Browse Dulora's dim to warm LED range and warm white LED globes to find the right colour temperature for every room.

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