What the Lux? Lux vs Lumens Explained

By Conrad Knuist · Head of Marketing and Photography Specialist · 18+ years in photography

Shopping for a video light can feel like reading a maths exam. One spec sheet boasts 6,000 lumens, another promises 30,000 lux, a third lists watts, and none of them seem to agree on which number actually tells you how bright the light is. So, what the lux is going on?

The short answer: lumens and lux measure two different things. Lumens tell you how much light a fixture produces in total, while lux tells you how much of that light actually lands on your subject.

The Simple Version

Lumens leave the light; lux is what lands on your subject

How the lumen measures total light output, per Lumen (unit), Wikipedia.

How lux measures light falling on a surface, per Lux, Wikipedia.

Why Lux Changes With Distance

As light travels away from a source, it spreads over a larger and larger area, so less of it lands on each square metre. For a small light source, this follows the inverse square law: double the distance and the lux drops to roughly a quarter. Triple the distance and it drops to roughly a ninth.

You can see it in real photometric data. The amaran Halo 60x, a compact COB LED we stock, measures 3,270 lux at 1 metre with no modifier at 6,500K. Move to 3 metres and it reads 375 lux, almost exactly the one-ninth the inverse square law predicts. Same light, same lumens, but your subject gets far less light the further away it is.

Photometric figures as published by the manufacturer, amaran.

For photographers this is also handy maths. Since each stop of exposure doubles or halves the light, moving a light from 1m to about 1.4m costs you roughly one stop, and moving it to 2m costs roughly two stops. Bringing a light closer is often the cheapest way to get more brightness.

Why light falls off with the square of the distance, per Inverse-square law, Wikipedia.

Why Modifiers Change the Lux Number

Modifiers do not create light, but they decide where it goes, and that changes lux dramatically. A reflector or fresnel concentrates the light into a narrower beam, so more of it lands on your subject. A softbox or diffuser spreads it out, so the light is softer but less intense at any one point.

The Halo 60x shows it clearly. The light produces the same lumens in every case; the modifier simply focuses it:

Photometric figures as published by the manufacturer, amaran. Modifiers sold separately.

Important: Why Reflector Lux Numbers Can Mislead

A reflector or fresnel does not create any extra light. It takes the same lumens and squeezes them into a smaller circle, and the light meter on a spec sheet sits right in the middle of that bright spot. The number is accurate, but it describes a small hotspot, not how much useful light you actually have.

• Smaller coverage: the light covers a much smaller area, so it may light a face but not a full-length figure or a group.
• Harder light: a focused beam gives harder shadows, which is not what most portrait and interview setups need.
• Uneven light: the reading is taken at the brightest point, and brightness falls away towards the edge of the beam.
• Gone in a softbox: the moment the reflector comes off and a softbox goes on, the headline number no longer applies.

So a reflector lux figure is genuinely useful if you plan to shoot with that reflector, for example to throw light across a large space or compete with bright daylight. For most other work, compare bare figures, or the same modifier on both lights.

Important: Lower Lux Does Not Mean Less Light

The flip side matters just as much. When a light spreads its output over a wider area, the lux at any one point drops, but the light has not disappeared. A wide beam, a panel, a tube, or a large softbox will often show a lower lux figure than a focused spot, yet light a whole set more evenly.

Different lights are built for different jobs. Fresnels, reflectors, and projection attachments concentrate light for punch and reach. Panels, tube lights, lanterns, and big softboxes spread it for soft, even coverage. Neither is better, so read every lux figure in the context of what that light is designed to do. One caveat: diffusion fabric does absorb a little light, so spreading light costs a small amount of total output, but far less than the drop in lux suggests.

Same Wattage, Different Lux? Godox LE vs LA

You may spot two lights in the same power class with very different lux numbers. A good example is the Godox LITEMONS LE300Bi and LA300Bi, both bi-colour COB lights in the 300W class. Bare, their figures are fairly close. Add each light's own reflector and the gap more than doubles:

As specified by the manufacturer, Godox.

Most of that headline difference comes from the reflector, not the light. The LA300Bi's reflector focuses its beam into a tighter spot, which reads far higher at the centre. Bare, the LA300Bi is brighter by roughly a fifth, nowhere near the two-times gap the reflector figures suggest, and in a softbox the two will be closer still.

Wattage adds to the confusion. Watts measure how much power a light draws, not how much light it produces, and efficiency (lumens per watt) varies with the LED chip, cooling, and optics, so lights with similar wattage can output different amounts of light. Bi-colour lights are also often measured at their brightest colour temperature, so check which one a figure refers to.

Why Lux Changes With Colour Temperature and RGB Colours

Spec sheets often list different lux figures for the same light at different colour temperatures. That is not a typo. Here is a typical example, the amaran Halo 60x, bare, at 1m. Warm settings come in around a fifth lower than cool:

Photometric figures as published by the manufacturer, amaran.

Two things are going on. Warm-white LEDs are generally a little less efficient than cool-white ones, so warm settings produce slightly less light. And a bi-colour light blends two banks of LEDs, warm and cool, so its total output shifts across the range rather than staying identical at every setting.

Bi-colour lights blend warm and cool LEDs, so output shifts across the range

RGB colours vary far more. Lux is not a measure of raw energy: it is weighted to match the human eye, which is most sensitive to green and yellow and much less sensitive to deep red and blue. A saturated blue can carry plenty of energy yet register very low lux. A pure colour also often uses only one or two of the light's LED channels, while white uses them all. Expect deep blues and reds to measure far below white, and greens to read comparatively high.

This table shows how strongly the eye, and therefore a lux meter, weights each colour for the same amount of light energy, with green as the reference:

Based on the standard photopic luminosity function. These show how the eye weights colour, not the output of a specific light; real RGB lights vary with their LEDs and colour mixing.

Saturated colours, especially deep blue and red, measure far lower than white

The takeaway: compare lights at the same colour temperature, ideally the one you shoot at most, and expect coloured light to need more power or a closer position. Your camera also sees colour differently from your eye, so test exposure rather than trusting a lux figure for saturated colours.

How brightness is weighted to the human eye's sensitivity, per Luminosity function, Wikipedia.

Lux or Lumens: Which Matters More for Photographers and Videographers?

For most photo and video work, lux is the more useful number, because exposure depends on how much light reaches your subject, not how much leaves the light. But lux only tells the truth in context: at a known distance, with a known modifier, at a known colour temperature.

Lumens earn their place when a light is going into a softbox or other diffuser. The softbox spreads the light anyway, so what matters is how much light the fixture makes in total, and lumens, or bare lux figures measured the same way, are a better guide than reflector numbers. In short:

• Lighting a subject directly or with a reflector: use lux, at the same distance, modifier, and colour temperature.
• Using softboxes and diffusion: compare bare lux or lumens.
• Understanding a light's total output: lumens are a fair overall measure, especially for room or ambient lighting.
• Planning power and batteries: use watts.
• Judging colour quality: none of these. Look at CRI, TLCI, or TM-30 instead, because a bright light with poor colour still looks wrong on camera.

The most useful habit is simple: whenever you see a lux figure, ask "at what distance, with what modifier, and what is this light designed to do?" If two lights are measured the same way, the comparison is fair. If not, the numbers do not tell you much.

Conrad Knuist

Head of Marketing and Photography Specialist

Conrad Knuist is Head of Marketing and Photography Specialist at CameraStuff, South Africa's specialist camera and lighting retailer. With over 18 years of hands-on experience across portrait, event, and commercial photography, Conrad has personally handled hundreds of lights and helps South African creators make sense of spec sheets.

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