Lumen, Lux & Candela – an introduction

Lumen (lm), lux (lx) and candela (cd) are units of measurement used to describe the output of bulbs and light fittings. With incandescent and halogen lighting it was always easy to equate wattage with light output, because the same wattage always produced the same amount of light.

Now that different technologies have entered into the equation, using wattage as an indicator of output has become increasingly obsolete. In retrofit CFLs or LEDs, and even energy-saving halogen lamps, an equivalent incandescent or halogen wattage is given by manufacturers to make life easier.

Like-for-like comparisons between modern light sources are complex, since their output per watt varies considerably from one product to the next. Therefore, more universal units of measurement are required – measurements that actually record light.

Lumen, lux, and candela are definable as follows:

Lumen (Lm)

Lumens measure the total amount of light energy from any source, regardless of direction. The lumen answers a simple question: how much light does this source produce?

When buying modern bulbs you’ll find the lumen measurement added to the packaging and stated prominently – usually at twice the size of the wattage.

Lumens are used to measure energy efficiency, using a lumens-per-watt formula. In the lighting industry this formula is called ‘luminous efficacy’. Efficacy refers to a ratio between two different units of measurement.

Sometimes lighting manufacturers give a ‘LOR’ measurement (Light Output Ratio), which accounts for the percentage of light in lumens wasted between the source and transmission through a light fitting.

A guide to the energy efficiency (or luminous efficacy) of various technologies is as follows:

Lux (Lx)

Lux is a unit of illuminance equivalent to 1 lumen per square metre. It is a measurement given in conjunction with distance, or a set of incremental distances, so that end-users can gauge whether a lamp or luminaire delivers an adequate intensity of light for specific applications, or to meet building regulations. For instance, corridors are often required to measure a minimum 100 lux at floor level (typical height around 3m), and 300-500 lux is recommended for reading.

The Lux measurement is normally used with products that have a fixed spread of light (beam angle) such as GU10 bulbs or downlights.

The illustration below shows an example of decreasing light levels over distance: 0.75m = 3500lx, 1.5m = 800lx, 2.15m = 400lx, and 3m = 150lx.
A diagram explaining how Lux works

Candela (Cd)

Candela is a measurement of luminous intensity at source, and in a given direction. One candela is the approximate equivalent in output of a traditional candle. A candela measurement differs from lumens in that it measures directional intensity rather than the overall amount of light, so it takes no account of multidirectional output. For that reason candelas are used primarily to measure focused lamps, such as spotlights.

For more information, advice and ideas take a look at our Lighting Advice section.

Charles Barnett Managing Director

Charles started Lyco in 1995 with just 4 enthusiastic employees and has grown it considerably over the past 25 years. Charles is also the Managing Director of Lighting Direct and newly acquired Online Lighting. He now has a team of 50 lighting experts working on growing Lyco Group to be the UK leader in lighting for both businesses and homes. Away from the office he is a keen cyclist and is proud to have cycled 1017 miles from Lands End to John O’Groats to raise money for a new residential centre for adults with multiple learning difficulties.

SAD lights – fluorescent tubes to fight depression

Ask most people if they prefer a sunny day to a cloudy one, and you’ll doubtless get a silly answer! We may not always realize it but the Sun is our feel good source, and for quite a few of us the winter months, which feature less and less sunlight, provides a real challenge to the way we feel. That’s where an SAD light can help. SAD lights brings the benefits of the Sun indoors and helps fight off the blues for many people who knowingly or not are SAD sufferers.

What is SAD?

Seasonal Affective Disorder (SAD) is a form of depression commonly associated with lack of exposure to sunlight during winter months. Symptoms include low mood and profound lack of motivation. Tiredness and a constant desire to sleep are also indicators. Such symptoms always warrant the attention of a GP, as they can be difficult to surmount alone.

Physical causes

Lack of sunlight adversely affects production of melatonin and serotonin hormones in the body, causing SAD. This imbalance can be helped naturally by a SAD lamp and other remedies.

Melatonin helps to regulate the body’s circadian rhythm (body clock) and produce sleep. Sufferers of SAD often have higher than average amounts of melatonin in their body during winter months.

Serotonin is a neurotransmitter affecting multiple human functions, including sleep, appetite, mood, and nerve cell communication. Lack of exposure to bright, natural light decreases the body’s production of serotonin, and low serotonin levels are commonly linked to depression.

The role of light in SAD

One of the chief treatments for SAD is bright light therapy. This involves the patient being exposed to an intense artificial light of remarkably high quality, resembling daylight as closely as possible. Most UV radiation is removed from the light source, to avoid damage to either skin or eyes.

Treatment times vary not only between patients, but also according to the intensity of light. A 2,000 to 10,000 lux light is typically used, which is many times stronger than any regular bulb. Thirty minutes to three hours of treatment per day is normal.

If circumstances permit, regular walks and plenty of exposure to natural daylight are prescribed for most sufferers of depression. SAD is often caused when work prevents this possibility (it is common in night-workers, who generally sleep through winter daylight).

A supporting role – daylight is not enough!

As a preventive measure or to support ongoing SAD treatment, products such as SAD tubes or SAD lights are available. These closely match daylight in most respects, except for sheer intensity.

To deal with a misconception, for a bulb to actually behave like daylight, it is not enough for it to emit a 6500K daylight colour temperature. Although this is a useful quality, it has to be combined with exceptional colour rendering. A near-maximum 98% Colour Rendering Index (CRI) score always indicates this.

This combination of critical colour rendering and a daylight colour temperature is very rare in electric lighting. Incandescent is arguably the best light source for colour with a default CRI 100 score, but the filament of a lamp would melt before it resembled daylight in overall colour.

At the high end of the LED market, products with outstanding colour rendering are emerging, but they’re expensive and meant for other purposes. For health applications, a fluorescent SAD tube offers an easy, affordable answer to improving indoor light quality.

Fluorescent SAD tubes

Lyco stock a choice of three different Sylvania SAD Activa 172 Fluorescent Tubes, in 18 watt, 36 watt, and 58 watt versions.

From a health perspective, the most important point about these tubes is their ‘full spectrum light’, as Sylvania and other manufacturers call it. But what is this?

In marketing, ‘full spectrum light’ refers to a light source that emulates daylight in its colour-rendering ability and colour temperature. Other daylight or sunlight qualities might be implied, especially UV radiation in a fluorescent tube. This is useful for producing vitamin D in the body, which affects the normal functioning of the nervous system.

Sylvania SAD Activa tubes meet all of these criteria. They radiate at all wavelengths of the visible spectrum (i.e. all visible colours exist in their light), with an overall 6500K colour temperature. They also radiate outside of the visible spectrum to produce a safe amount of UV light.

When a light source covers the entire visible spectrum, it scores a very high or maximum CRI rating by default. It’s a property that trumps the Colour Rendering Index. The Sylvania SAD Fluorescent Tubes have a CRI 98 score, which signifies outstanding colour rendering.

How will these lights help fight SAD?

With SAD tubes installed, everything falling under their light will look natural, as if being lit by neutral window light. Colours will be enlivened and rendered accurately. The tubes will reduce eyestrain, headaches, and tiredness, and they’ll stimulate energy.

Light intensity and quality affects serotonin and melatonin levels in the body. This is the basis for bright light therapy and exposing SAD sufferers to as much good-quality light as possible.

Installing SAD tubes

The energy-efficient Sylvania SAD Fluorescent Tubes come in a standard T8 size, which is a 1” diameter tube with a double-ended G13 cap. They will slot into any existing T8 linear fluorescent light fitting. A long average lifespan of 14,000 hours adds to their exceptional value.

To take a look at our full range of SAD lights.

For more inspiration, advice and ideas take a look at our Lighting Advice section.


Andrew Evangelidis Head of Buying

Andrew is an experienced buying professional who takes an entrepreneurial approach to identify new lighting solutions and ensure Lyco have first-to-market ranges for our customers. Having previously worked for well known brands such as Wickes, Carphone Warehouse and Toys R Us, Andrew has now turned his hand to sourcing commercial lighting and ensure our customers receive top brand quality products at marketing leading prices. He manages a team of commercial and decorative buyers who travel the world finding new products that our customers don’t even know they need yet.

Top 10 Outdoor lights – the bestsellers

Edit Cloud 600 Outdoor Ground Feature Light - White

There are so many outdoor lights to choose from, it can be hard making a choice when it comes to creating the right ambience for clients, customers or employees. With the British weather usually being on the unpredictable side, we have brought together the top ten outdoor lights that will help you make the most of your outdoors. From security lights to LED planter lights, we cover the whole range of outdoor lights, with one or two suggestions that will hopefully fulfill your needs! But what’s top of our charts and do you agree with us? Take a look at our countdown to find out…

10. Edit Cloud LED Ground Light

An outdoor light that makes a wonderful contemporary statement. Your customers or clients will love sitting in the garden with these inviting Edit Cloud ground lights dotted around the garden. LED Clouds are perfect for hotel, restaurant or bar gardens.

9. Edit Dune Post Light

The Edit Dune Post Light is very sleek and brings a sophisticated, contemporary look to your premises, thanks to its thin design and stainless steel casing .Its IP44 rating makes it suitable for life outside. Use it to light up garden paths, or driveways for your employees and customers, allowing them to work or relax in comfort. Create soft, ambient lighting with these wonderful outdoor post lights.

8. Nordlux Twin Wall Light

Nordlux Twin PIR Wall LightCarrying on the theme of sleek and contemporary is the Stainless Steel Twin Wall Light, which gives a column of light both above and below the fitting. This outside light is perfect for creating ambient lighting outdoors. It has a quality Danish design that won’t let you down – perfect for use in public places.

Its durable IP54 Rating means it can withstand the harsh outdoors without losing function.

7. Albany Walkover Light

Albany Walkover LightsNext we have the Albany walkover light. This submersible light has an incredible IP68 Rating. Completely watertight, this durable light is perfect for lighting paths and decking where water might accumulate. It can even withstand water up to 1m deep – use it to illuminate water features, ponds and waterfalls. This is a great tool if revamping a garden for clients or if you want to set your hotel, restaurant or pub grounds apart from others.

6. Twin LED PIR Floodlight

Twin LED PIR Floodlight
Keep you, your premises, customers and employees safe with this Searchlight LED Twin Flood Light with PIR Sensor. What better way to feel safe and secure on your premises after dark than with this LED Floodlight. This outdoor security light is incredibly low energy; it’s equivalent to 70W incandescent light output and yet uses only a fraction of the energy. Work or relax with the peace of mind that quality security brings.

5. Vejers Down Wall Light

Vejers Black Down Wall LightBring a touch of Scandinavian design to your garden with this Vejers down wall light – Galvanised. Incredibly sturdy and durable with an IP54 Rating, in its galvanized finish, this light functions fully even when exposed to harsh elements in coastal locations. Use it to light up the outside of buildings, even in exposed weather and rest assured it won’t let you down. The downlight design also makes it a good tool for lighting up areas of outside space you want to be seen such as plant displays.

4. Twilight Ground Lights

Mini Cool White LED Outdoor Ground Light - Steel
Next up we have the Mini Cool White LED Ground Light, which come complete with everything you need to install instant glamour to an outside decking space. These outside ground lights fit your decking no matter what the size. These decking lights come in a variety of colour temperatures to make your decking area a cosy ‘inside’ area, outside.

3. Protect Wall Light

Horizon Bulhead (Louvre)At three, we have the Protect Wall Light, which is completely rain and weatherproof thanks to a brilliant IP66 Rating. Vandal proof and completely energy efficient, this excellent light reduces glare and enables you to direct the light exactly where you need it, helping your employees or clients to work or relax in comfort.

2. Luxembourg PIR Wall Light

Luxembourg PIR Wall Light The Luxembourg PIR Wall Light combines the best of everything. It looks beautiful and has a unique design that won’t go out of fashion. This outside wall light has been made with incredibly durable galvanised steel and has a quality Danish design, which has been designed to withstand harsh weather conditions as seen on the coast. It has an amazing fifteen year anti-corrosion guarantee, which displays how much faith the manufacturer’s have in it. An excellent IP54 rating means it won’t let you down, even when exposed to the harshest elements. A PIR motion sensor helps keep you, your premises and the people you look after, secure.

And here it is! As voted by us…

1. GuardCam LED Security Floodlight

The best light for a British SummerThe GuardCam LED Security Floodlight is an amazing all-in-one PIR security light, speaker, DVR system and camera. It not only light up your premises when it senses motion, but also records whatever has triggered the sensors directly on to an included 2GB SD memory card. You can choose between still frames or video format while the latest LED technology ensures that even night time footage is seen colourfully and clearly. Whether you want to guard commercial or domestic properties or grounds, this brilliant floodlight won’t let you down.

Don’t forget to scour the rest of our outdoor lights.

Looking for more news, inspiration and advice? Try our Lighting Advice section.

Charles Barnett Managing Director

Charles started Lyco in 1995 with just 4 enthusiastic employees and has grown it considerably over the past 25 years. Charles is also the Managing Director of Lighting Direct and newly acquired Online Lighting. He now has a team of 50 lighting experts working on growing Lyco Group to be the UK leader in lighting for both businesses and homes. Away from the office he is a keen cyclist and is proud to have cycled 1017 miles from Lands End to John O’Groats to raise money for a new residential centre for adults with multiple learning difficulties.

Top 10 Bathroom lights (and where they can go)

bathroom lighting

Choosing bathroom lights is not easy, not only because of the choice of styles available but also because the lights need to be up to the demands to be placed on them, in terms of positioning.

To give you a helping hand in your search for the perfect bathroom lighting we have pulled together our top 10 bathroom lights, which should offer you some great inspiration, whilst also letting you know exactly where in the bathroom these lights can be safely placed.

Important bathroom lighting guidance

It is essential when buying bathroom lights that you take into account the light’s IP Rating and know which Bathroom Zone it is suitable for, otherwise the light will either not perform as you want it to, won’t work at all or worse still will pose a potentially life threatening electrical hazard in your home. Always remember to check!

Our top 10 bathroom lights

Here is a top 10 list of some of our most popular bathroom lights, with suggestions as to where they might be installed:

Robus – Garland LED Walkover Lights (Zone 0)Garland LED Walkover lights from Robus

These little IP68-rated LED lights are fully protected against immersion, and ideal for use in Zone 0 areas such as shower trays and baths. Being LED they’re naturally shock proof, vibration proof, and cool to the touch, so they’re ideal for this application. A choice of blue or white colours is available.

Eterna – Carina 28W Flush Fitting (Zones 1 & 2, outside zones)

Offering great value for money, this versatile fitting can be wall or ceiling mounted, and provides splash-proof protection against water. The IP44-rated Carina is available in a choice of finishes, and includes a tough polycarbonate diffuser that protects against accidental or deliberate breakage.

Dar Lighting – Bueno Twin Wall Light (Zones 1 & 2, outside zones)Bueno Twin Wall Light from Dar Lighting

Stylishly designed, the modern-looking Bueno has an IP44 rating. This is an elegant bathroom lighting solution with twin frosted glass diffusers and smart polished chrome finish. An on/off pull cord allows convenient independent operation.


Dar Lighting – Zodiac Mirror Light (Zones 1 & 2, outside zones)

This smartly designed fitting exploits the compact nature of LEDs, twenty of which discreetly line the left and right edges of the mirror. The IP44-rated Zodiac Mirror Light is ideal for installation in zone 2 or outside zone areas above a wash basin. It is available in a choice of sizes and with or without shaver sockets.

Astro Lighting – Trimless Low Voltage Fire Rated Downlights (Zones 1 & 2, outside zones)

In any bathroom or washroom where jet cleaning is undertaken, an IPX5 rating is required. This neat lighting solution from Astro has an IP65 rating, making it dust-tight and resistant to jets of water. Also fire-rated, this recessed fitting can be safely installed below occupied floors, maintaining the integrity of the ceiling in the event of a fire. A mains-powered version of this light is also available.

Searchlight – Prato Flush Fitting (Zones 1 & 2, outside zones)Prato Flush Fitting Bathroom Light from Searchlight

Representing great value for money, this low-profile contemporary ceiling light has a beautiful chrome and glass finish, with a frosted inner circle of glass around the diffuser. An IP44 rating allows plenty of leeway in terms of positioning.

Eterna – Coronation Shaver Light (Zone 2 & outside zones)

This fitting provides plenty of light for shaving duties, and with an IP44 rating it’s designed to withstand the odd wayward splash of water. The Coronation Shaver Light has an independent on/off pull cord and dual-voltage shaver sockets. Eterna recommend zone 2 installation or dry areas for this fitting, which allows any area around a wash basin.

Robus – Crystal Bathroom 4-Light Plate (Zone 2, outside zones)Crystal Bathroom Ceiling Light

The Crystal Bathroom 4-Light Plate protects against water splashes with an IP44 rating, and produces a bright, sparkling light from a quad of sealed glass cubes. Inside the cubes are halogen G4 capsules, fed by an integrated low-voltage transformer. Robus advise installation of this fitting in zone 2 or outside zones.

Eterna – LED Shaver Light (outside zones)

With its IP44 rating, this fitting is intended for use in dry areas. Typically this will be above the zone 2 radius of a bathroom wash basin. Offering superb value for money, the Eterna Shaver Light includes dual-voltage shaver sockets and a convenient on/off pull cord.

Overriding decisions

Occasionally you’ll find manufacturer’s instructions that recommend more conservative use around water than is suggested by the IP rating. This should always be checked before installation.

For complete peace of mind and understanding take a look at our IP Rating and Bathroom Zones guides, and if in any doubt always consult a qualified electrician.

For more lighting options, don’t forget to check out our full range of bathroom lights. Alternatively if you’re looking for more news, inspiration or advice, try our Lighting Advice section.

Charles Barnett Managing Director

Charles started Lyco in 1995 with just 4 enthusiastic employees and has grown it considerably over the past 25 years. Charles is also the Managing Director of Lighting Direct and newly acquired Online Lighting. He now has a team of 50 lighting experts working on growing Lyco Group to be the UK leader in lighting for both businesses and homes. Away from the office he is a keen cyclist and is proud to have cycled 1017 miles from Lands End to John O’Groats to raise money for a new residential centre for adults with multiple learning difficulties.