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Guides · Lighting knowledge

Understand light, then buy.

By Seydhan Cakmak · TopLampenReviews editorial team
Last updated: July 2026

AI-assisted text, editorially reviewed · Images are real product photos, not AI images · Details

Key answer Good light can be planned: lumens describe how bright a lamp shines, kelvin the colour of its light and lux the brightness that arrives on a surface. Once you have understood these three values, you no longer buy lamps by watts or looks, but by effect. That is exactly where our six guides lead: from the lumens-to-watts chart through the kelvin scale and the question of lumens per room to sleep, eye comfort and running costs. For quick practical use, the lighting calculator works out your room's lumen requirement in under a minute. We deliberately link products in this section only at the margins, because understanding comes first here.

A good buying decision does not start with the lampshade, but with the light. That is why we gather here the basics that matter before every purchase: why watts no longer measure brightness, which kelvin figure creates which mood, how many lumens a room really needs, what blue light in the evening does to sleep, what eye-friendly work lighting looks like when working from home and what an LED costs in electricity over a year. All of it honest, easy to understand and without sales pressure.

The kelvin scale above is our guiding theme: each article sits somewhere between candlelight and daylight. If you want to get started straight after reading, the buying guides of the categories are waiting, for example on floor lamps for the living room or SAD lamps for the dark months, and the lighting calculator turns the theory into a concrete recommendation for your room.

Six articles

From the watts question to the electricity bill.

Six guides cover the questions that come up before every lamp purchase. Read up before you buy: your eyes, your sleep and your electricity bill will benefit.

01 Basics

Lumens instead of watts: the conversion chart

60 watts no longer means brightness: which lumen figure replaces the old light bulb, with a large chart from 25 to 100 watts and the most important buying rules for LED.

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02 Basics

Colour temperature explained: the kelvin chart

Warm white, neutral white, daylight white: which kelvin figure belongs in which room, from candlelight mood at 1,500 K to daylight at 6,500 K.

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03 Planning

How many lumens per room?

Lux guide values for living room, kitchen, bathroom and workplace, plus simple ways to calculate from square metres to lumens and the most common planning mistakes.

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04 Health

Light and sleep: blue light honestly put in context

Why evening light should be warm, what blue light does to melatonin and how wake-up lights ease dark winter mornings, calmly explained.

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05 Home office

Working in an eye-friendly way from home

Glare-free work lighting with around 500 lux: how desk lamp, monitor and room lighting work together so that your eyes last the working day.

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06 Costs

LED power consumption and costs

The simple calculation from watts to kilowatt-hours, what LED saves compared with halogen and how you spot the power-hungry lights on the ceiling.

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Nineteen practical questions

When it gets concrete: technology, installation, health.

The six basics above explain the principle. This collection answers the questions that come up afterwards in everyday life: from flickering LEDs and smart lamps on the wall switch to the right mounting height and how to use a SAD lamp. One click takes you straight to the answer, and the lighting glossary looks up every technical term from A to Z for you.

07 Smart lighting

Smart lamps on the light switch

Why smart lamps and the normal wall switch clash, and three clean solutions: switching actuator, wireless switch or fixed switch.

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08 Smart lighting

Standby consumption of smart lamps

What smart lamps draw at rest: typically 0.2 to 2 watts, with the calculation for electricity costs per year and tips for saving.

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09 Smart lighting

Hue Bridge limit: how many lamps fit

Around 50 lamps on the classic Hue Bridge, significantly more on the Bridge Pro, plus the calculation for a multi-bridge setup.

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10 Troubleshooting

LED flickers: narrowing down the causes

The four most common causes of flickering LED light and how to narrow them down in five steps: dimmer, transformer, base load, light bulb.

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11 Troubleshooting

LED glows after switching off

Does the LED keep glowing faintly after switching off? The 2-minute diagnosis tree finds the cause and safely stops the afterglow.

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12 Troubleshooting

Solar lamp does not light up: troubleshooting

When the solar light stays dark: systematically check the protective film, switch, location and battery and fix it in a few minutes.

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13 Basics

Maximum watts of the lamp holder

Is the lamp limited to 60 watts? That figure stands for heat, not brightness. The chart shows which LED can safely go in.

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14 Installation

Fixing a lamp to a concrete ceiling

Wall plugs, adhesive or hooks: how to hang a lamp safely from a concrete ceiling, graded by weight and with notes for tenants.

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15 Installation

Pendant light above the dining table

How high and how big: 60 to 75 cm above the tabletop, plus the formula for the right diameter and the right colour temperature.

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16 Upgrading

Converting an uplighter to LED

Making a halogen uplighter more economical: determine the R7s cap length, choose the LED tube by lumens and kelvin, avoid dimmer problems.

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17 Home office

Lumens for the desk lamp

How bright does it need to be at the desk? For reading and screen work around 400 to 600 lumens and 500 lux, more for detailed work. Chart by task.

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18 Concentration

Which light for studying?

Which colour temperature keeps your mind awake: 4,000 to 5,000 kelvin and around 500 lux, plus the role of brightness and breaks when studying.

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19 Home office

Are monitor light bars worth it?

Screen bar on the monitor: who a monitor light bar is really worthwhile for, when it is unnecessary and what matters when buying, honestly weighed up.

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20 Health

Using a SAD lamp correctly

Duration, time of day and distance: how to use a SAD lamp correctly, with a lux, duration and distance chart and an honest health note.

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21 Health

Does health insurance pay for a SAD lamp?

It is usually decided case by case: how to proceed with a medical prescription and an application, and what the insurer checks in the process.

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22 Health

SAD lamp: side effects

What side effects a SAD lamp can have, who should take care and how you avoid headaches and irritated eyes.

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23 Health

Light therapy for shift work

When early, late and night shifts need bright light and when darkness protects sleep: the right timing for each shift type.

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24 Basics

E27 or E14?

The difference lies in the thread: 27 versus 14 millimetres. Sizes, places of use, adaptors and which cap goes where.

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25 Planning

IP44 or IP65 in the bathroom?

Which IP rating goes where: bathroom zones 0, 1 and 2 simply explained, for the ceiling, the mirror and above the shower.

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26 Basics

GU10 or E27?

Twist-lock cap versus screw thread: which cap is meant for spotlights and which for lamps, with a choice by use.

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Look-up

The lighting glossary

Around 25 technical terms from lumens, lux and kelvin through CRI and UGR to Zigbee and Matter: explained briefly, alphabetically and in a citable form.

Look up →
Interactive · Guides as a tool

Calculate first, then buy: the lighting calculator.

Room, area, use, colour temperature: the calculator turns the formulas from these guides into a concrete recommendation of how many lumens your room needs and which kelvin figure suits it. No sign-up, no tracking, straight in the browser.

Start the calculator →
From knowledge to lamp

And when you are ready: the buying guides.

Each guide links the matching categories in the text. Here is the direct route to all five areas and to the light bulb guide.

2,700 K · Homely

Floor lamps

Warm white living room light: tripod, arc lamp, uplighter and smart light columns honestly compared.

To the guide →
4,000 K · Focused

Desk lamps

Glare-free work lighting for desk and monitor, from the clamp lamp to the screen bar.

To the guide →
10,000 lx · Bright as day

SAD lamps

Bright light for dark months and wake-up lights for gentler mornings, honestly put in context and without promises of healing.

To the guide →
16 million colours · Smart

Smart lighting

Hue, WiZ, Govee and Matter: systems, smart light bulbs and LED strip lights compared.

To the guide →
Ceiling to garden

Home lighting

Ceiling lights, bedside lamps and outdoor lighting: the light for the rest of the house.

To the guide →
E27 · GU10 · E14

Light bulbs

The right LED for every cap: brightness, colour temperature and dimmability when buying a light bulb.

To the guide →
Frequently asked questions

Frequently asked questions about lighting knowledge

The questions that reach us most often about lumens, kelvin and good light, briefly answered and linked to the matching guide.

Where do I start when planning the lighting of a room from scratch?

Start with brightness: use the lux guide values to work out how many lumens your room needs in total, which our guide on lumens per room explains. Then choose the colour temperature according to use and spread the light across several sources instead of a single ceiling light. If you prefer the easy route, the lighting calculator works out both for you in under a minute.

What is the difference between lumens, kelvin and lux?

Lumens state how much light a lamp gives off in total, kelvin describe the colour of that light from warm to daylight white. Lux measure how much of that light actually arrives on a surface, such as your desk. For buying a lamp you usually only need lumens and kelvin, for room planning you also need the lux guide values.

How many lumens replace an old 60-watt light bulb?

As a rule of thumb, around 806 lumens correspond to the classic 60-watt light bulb. According to manufacturer data, an LED typically reaches this brightness with just 7 to 10 watts. You will find the full conversion from 25 to 100 watts in our lumens-to-watts chart.

Is cool white light in the evening really a problem?

Cool white light contains high blue components, and these can suppress the sleep hormone melatonin more strongly than warm light. For the evening we therefore recommend warm white, dimmed light of at most 2,700 kelvin. Our guide on light and sleep explains the connections, honestly and without scaremongering.

Do you also link to products in the guides?

Deliberately only sparingly in the knowledge articles: they are meant to explain connections, not to sell. You will find concrete recommendations with labelled affiliate links in the buying guides of the categories, for example for floor lamps or desk lamps.