What is the Difference Between Lumen and Lux?
Lumen is the measurement/output of light produced from a lamp.
Lux is the measurement of light at a specific point or position.
Lumens can be split into 2 groups: Raw Lumens & Effective Lumens
Raw Lumens is the light output quoted by the manufacturer of the LED.
Example: Cree XM-L2 10w LED has a Manufacturer Raw Lumen figure of 1050 Lumens. If you have 8 of these in 1 lamp the Raw Lumens for that lamp is 8 x 1050 = 8400 Lumens Raw.
Effective Lumens is the actual measured Lumen figure that takes into account real losses e.g. Thermal loss, Optical Loss & Assembly loss.
Example: Thermal loss, Optical Loss & Assembly/Circuitry/Electronic loss, can equate/effect up to 25% typical lumen loss eg: 8400 Raw Lumens = 6300 Effective Lumens. Other lighting companies have up to 35% Lumen loss due to bad thermal designs, bad housing designs and cheap optics.
Lux is a world-wide term for the measurement of light on a specific surface. It requires the use of a lux meter which measures the light output. 1 lux of light is equivalent to a full moon at night in good atmospheric conditions.
What is the Relationship Between Watts & Lumen?
Since LEDs have been introduced into the market 10 years ago there has been a confusing array of new terms and phrases to explain how much light they produce. A number of manufacturers have used this confusion to peddle dodgy and substandard products without being detected. One of these clichés is watts vs lumens.
Let’s deal with the Watts first. The wattage of the lamp can be described as the total current draw of the lamp as a system or just taking into account what the LEDs draw i.e. 6 x 10W LEDs = 60W. The difference can be between 5 and 10% as the other components on the pc board also draw current. This could mean that a 100W lamp (based on 20x5W LEDs) is actually drawing 110W if the LEDs are running at full wack. This is not too serious provided the wiring harness has been designed to cope with the extra current. (As an aside, if you are buying a lamp around the 100W level and you have bought a separate harness you need to be sure that it can handle the current draw. A common misconception is that LED’s ‘don’t draw much power’ and therefore anything will work. Perhaps not surprisingly, 100W of halogen power is actually the same current draw as 100W of LED power, so make sure your harness is up to spec.)
The other possibility is that the manufacturer claims 100W (20x5W LEDs) but only runs the LED’s at 3W to reduce the heat build-up and make them to last longer. This means that the lamp is technically a 100W but is actually only acting as a 60W. Bit disappointing if you were hoping to be seeing that ‘roo 1km down the road!
So then, what does the lumen value refer to then? Lumens is the theoretical amount of light produced by an LED. This value is established and proved by the LED manufacturer (Cree, LumiLed etc.) and is influenced by the amount of power input.
This is then split into two categories – raw lumens and effective lumens. What the manufacturer states as the lumens is Raw Lumens. This doesn’t take into account the system into which the LED is put or what current it is running at. They often state this value at a nominal temperature i.e. 25°C, which may have no bearing on the actual temperature of operation. All these things affect the lumens dramatically.
Effective lumens on the other hand is a measurement after the LED has been built into a system, or lamp. This takes into account these other factors and specifies at what temperature it is relevant at i.e. 70°C. This is the ‘junction’ temperature that is measured on the pc board, not the housing.
For most LED’s the harder you drive them the brighter they are but the less efficient they become. This can be a bit confusing but we can explain it like this. If you drive a 5W LED at 5W, it will produce, say, 20 lumens/watt. If you drive it at 2W it may produce 30 lumens/watt but will still not be as bright as the 5W running at a lower efficiency.
So when you’re considering buying some lights the most relevant measurement is likely to be the effective lumens, not watts. If a manufacturer doesn’t specify if the value is raw or effective, you can safely assume it is raw. However this is still not the whole story and needs to be balanced with the lux values as lumens still doesn’t tell you how the light is controlled. Having 10000 lumens of uncontrolled light may give you a massive ball of close up light, but won’t necessarily go more than 50 meters down the road!
What is the Kelvin Colour Temperature & What is Best?
The kelvin (K) of a lamp refers to the colour output or colour temperature of the light the lamps produces.
There is no absolute standard for colour temperature. Within the range of halogen and HID/LED everyone has different preferences and this is often influenced by the road you’re driving on and the weather conditions.
Traditional lighting like halogen and metal halide were on the lower end of the scale being about 2800K to 3500K. This is the yellow side of the colour spectrum and typically gives good definition at close range but doesn’t penetrate very far. When halogen lights on cars were popular (or should we say when nothing else was available) you often saw driving lights with blue covers. This was to filter the light to make it more white which some people find to look brighter. However, when applied using a cover it certainly wouldn’t have improved the distance at all.
With the introduction of HID’s and later LED’s, this colour scale moved dramatically up to the 6000K to 6500K level (even up to 8000K), which is white to blue-white in colour. This trend backed off slightly after a while due to a ‘haze’ effect produced by the blue-white light and also severe flash-back off road signs and 5000K-6000K is now much more common with only a few still going higher than this.
With the higher K rating definition also was impaired and although everything looked very bright, it was difficult to see detail. For a number of years this has been an argument to stay with halogen but being people, we all like different things and there is no one right answer.
Another issue is driving in mist or fog where the light bounces back and gives minimal penetration. This discovery has led to a reverting back by some to 4000K, either in more intelligently designed Halogens, HID’s or more recently 4000K LED’s. These 4000K LED’s obviously captures the benefits of solid state lighting, but largely overcomes the issues of the colour being too white.
For these reasons someone travelling mostly in the high country with regular mist and fog may prefer the 4000K. When you’re going round a mountain pass, trying not to be late for that appointment, reducing the glare from chevron signs around the bends is often desirable. Likewise they may be better off with a light bar rather than driving lights, but that’s another discussion. However, if you’re out in the plains, dead flat with nothing for miles around (except roo’s and cattle!), then the whiter light of a 5000-6000K is often appreciated. Traditionally the whiter light has given more distance but some of the new technology LED’s have overcome this issue, producing the same results from 4000K-6000K.
In the OE (original equipment) market many manufacturers still use halogen as standard for their headlights. This is because they are very cheap to make and also attract more aftermarket business due to not lasting very long. HID never really took off with the OE’s due to their unreliability but we are seeing more and more coming through with LED as standard. So another deciding factor could be to match what colour temperature that your headlights use. If you have halogen headlights, there are aftermarket kits available to upgrade to LED for most vehicles but you need to check the legality issues.
So in conclusion there is no right or wrong. Borrow a friends ute who has already bought some lights, check them out and decide. Alternatively there are some manufacturers who offer a money back guarantee so you can make sure you’re happy before you’re committed to a $1500 spend.
What is the Different Between Raw & Effective Lumens?
OK so you’re researching lights and have a massive range of options. So many things to consider, lies to detect, hidden whatnots and all the rest. You may have noticed that some manufacturers have a lumen value, others have a raw lumen and effective lumen value. First to note, if they don’t state if it is raw or effective, you can be sure it is raw. So, here’s the gist of what you’re looking at.
Lumens or luminous flux is the theoretical amount of light produced by an LED in ideal or laboratory conditions. This value is calculated by the LED manufacturer (LG, Luxeon etc.) and is affected or changed by the amount of input current, phosphor dome and other factors. The manufacturers produce hundreds of different types of LED’s, all for specific applications. Some need high output/size ration (driving lights) while others are focusing on reducing energy consumption, like for warehouse lighting. A very important part of the lamp is that the designer chooses an LED that is relevant to the application.
To understand the application of luminous flux or lumens we then have to further split it up into two categories – raw lumens and effective lumens.
What the manufacturer states as the lumens is Raw Lumens. This doesn’t take into account the system into which the LED is put or what current it is running at. They also often state this value at a nominal temperature i.e. 25°C, which may have no bearing on the actual temperature of how it is being used. For instance, a driving light may be operating at 70°C, which will dramatically reduce the raw lumen figures. How we control the light using a reflector or secondary optics also affects how much light comes out the front of the lamp. While the raw lumens remains unaffected, we can’t claim this value for the system or lamp we are producing as it is misleading. This raw, luminous flux is emitted in a very wide arc and is totally uncontrolled i.e. it is just a ball of light, so doesn’t give any indication of the actual performance of the finished product.
Effective lumens on the other hand is a measurement after the LED has been built into a system, or in our case, a lamp. This takes into account these other factors and specifies at what temperature it is relevant at i.e. 70°C. This is the ‘junction’ temperature that is measured on the pc board, not the housing. One way to improve the number is using open form reflectors as they tend to improve the raw-effective ratio, but that is another discussion.
For most LED’s the harder you drive them the brighter they are but the less efficient they become. This can be a bit confusing but we can explain it like this. If you drive a 5W LED at 5W, it will produce, say, 100 lumens/watt. If you drive it at 2W it may produce 120 lumens/watt but will still not be as bright as the 5W running at a lower efficiency. Generally speaking for a driving light we are wanting maximum punch for a sensible size package and energy efficiency is not really a consideration.
So when you’re considering buying some lights the most relevant measurement is likely to be the effective lumens, not raw lumens as this take into account all the other factors that drop the lumen value. As a final point of explanation, if you had a black lens cover over your lights, the raw lumen value would still be the same as claimed by the manufacturer, but the effective lumens would be zero.
However this is still not the whole story and needs to be balanced with the lux values (find out more on theour blog: lux vs lumens) as lumens still doesn’t tell you how the light is controlled. Having 10000 lumens of uncontrolled light may give you a massive ball of close up light, but won’t necessarily go more than 50 meters down the road!
What is CRI (Colour Rendering Index) & Is It important?
So, another wretched term to get my head around. In the old days of halogen life was simpler. There was only halogen. Now we have all these other options to confuse. However, there is some pretty good benefits that come if we can hang in there and get through the confusion.
CRI – What is it and how does it affect me? Colour Rendering Index to give the Wikipedia explanation is (as of May 2018) ….
A colour rendering index (CRI) is a quantitative measure of the ability of a light source to reveal the colours of various objects faithfully in comparison with an ideal or natural light source. Light sources with a high CRI are desirable in colour-critical applications such as neonatal care and art restoration.
Put a bit more simply, how much detail can we see. If you are studying something fast moving or in great detail it is important to have a very high CRI. This means that your eye can detect all the tiny differences in colour and shade, giving you the whole picture. To illustrate CRI have you ever tried to colour match clothing in a room using fluorescent lighting? Think you’ve got it right, walk into the sunlight and, hey-ho, that black was actually navy blue. This is because flouro’s have a very poor CRI and so your eye cannot make that judgement call. By contrast the sun is 100 on the scale, giving your eye the perfect conditions. Likewise with start, cold blue-white LED’s and HID’s. Traditionally houses have used incandescent bulbs, mainly halogen and tungsten. These give a warm homely feel but also help the colour matching because they naturally have a very high CRI and similar to that of the sun. The scale starts at 0 (no differentiation) and goes up to 100 which is what sunlight would produce.
When we apply this to vehicular lighting the same logic applies although there are heaps of other factors that affect our vision and awareness too. There is obviously a lot of difference between scanning the bush at 100km/hour for rogue roos and checking clothing colours at home. The speed, tiredness levels, overall lighting levels, other distractions etc. all make a big impact on our ability to figure out what is a bush or a kangaroo. Conventional wisdom is that the higher the CRI the better chance you have of detecting something before it’s too late. Our opinion is that this needs to be graded. Truth be told a very blue-white light of about 6500K+ causes a glare in which objects can be obscured. These lights do also have a poor CRI but is also made worse by the kelvin temperature.
Now at this point there is a bit of grey area around the relationship between colour temperature (Kelvin) and CRI. Most modern LED’s are around the 70 CRI mark compared to a halogen which would be nearer 90. Our belief is that in the case of driving it is possibly sufficient to say that choosing a kelvin temperature that suits your eye is likely to produce better results. Also just simply having sufficient light will be much more valuable than spending 2 years trying to find a driving light or light bar with a 90+ CRI. These are no doubt available but the other factors mentioned will have a far greater impact than if the CRI is 70 or 90.
Where CRI gets more important is when videoing or live streaming fast games like football, tennis and the like, or as mentioned, the vital task of colour matching clothes.
What Colour Temperature Gives the Best Light?
Why do Some Manufacturers use 10W and Others 5W LEDS?
5 years ago most the LED driving lights on the market seemed to use 10W LED’s. The general rule of thumb was that they offered maximum light output for the smallest surface area. A number of cheaper manufacturers were using 5W or 3W chips which appeared to be more to make the lights look bigger or longer but certainly didn’t produce a huge amount of light. An ‘economical’ imported 90W light bar was typically about 1m long, looking quite impressive – until you turned it on!
However, as time went on in became evident that controlling the temperature of a 10W LED was quite difficult, particularly if they were running at full tilt. It they were put in a static situation like a work light or idling car, you could have LED’s fail due to overheating. To overcome this problem most manufacturers started to throttle back to power and running a 10W at 6-7W (find out more about the difference between raw and effective lumens). This helps the heat build-up but reduces the main advantage of size/output ratio. An alternative way of controlling heat is to have a thermal management system in the pc board. This throttles back the power when the system gets too hot. This works quite well but still didn’t completely overcome the issue.
It also became clear that to create intelligent optics and reflectors, you got better control from more, smaller wattage LED’s than from a few large ones. This led to further improvements in controlling the distance and width of the beams to a point where in 2017 Ultra Vision achieved 1 lux at 1.2km along with a width of 100° from only 2 x 140W lamps.
Around 2015 the tide starting turning as more manufacturers like Cree, LG and Luxeon started to focus on the 5W chips. Increasing the light output and efficiency, along with many more options in CRI, colour temperature and the like. By contrast, development with the 10W chips seemed to slow or stop. As the volume on the 5W’s increased so did the difference between the 10W and 5W, to a point where most manufacturers have moved completely away from the 10W. Now, in 2018, most 10W LED’s cost twice what 2x5W LED’s cost.
During the early part of 2018 Ultra Vision changed over their last 2 products from 10W to 5W. This has resulted in improved performance and reduced cost.
Is a Light Bar Better than Driving Lights?
Well there’s a lot to this question and not all of it is based on facts and figures. If you owned a two door buzz box and someone said 9” spotties was the way forward, you’d probably get a second opinion. Likewise if you have a new-series Land Cruiser and someone recommended a 6” light bar you probably wouldn’t think much of their advice. Horses for courses is really how it works out and there’s a reason why both are currently in the market, although the differences are reducing by the month.
The traditional view is that driving lights are for distance and light bars are for width. While this was true 5 years ago, it’s not quite so relevant now. When HID was a big thing (remember that?) everyone believed they needed to see 5km down the road. With the invention of the light bar, people started to realise that the kangaroo they hit is actually right next to them, not 5km down the road. So started a battle of which was best, often resolved by having both. In fact this combination does actually work very well as long as you don’t mind the issues that come with HID.
Anyway, fast forward to today and we have Light Bars capable of 1 lux at 1km, LED driving lights giving 1 lux at 1.2km and we find that HID is not as important as it was. The battle field has changed but there is still a battle on. Driving Lights vs Light Bars, Light Bars vs Driving Lights.
So, there’s a good few aspects we can look at to try and get closer to a decision and narrow the options down. The three main points we believe are important are:
Driving Conditions
Where are you driving most? Is it high country, flat plains or a combination? Do you have a lot of feral animals and what is the verge condition like?
As we mentioned earlier the rule of thumb is driving lights for distance and light bars for width. While this still holds true it’s mainly because we buy one light bar and always buy two driving lights. The most common light bar fitted is 120W, typically around 20” (or 550mm for the younger lot). The most common driving lights fitted would be a pair of 9” 120W’s. Not surprising you get twice the distance then. The other reason for this logic is that when LED bars were introduced LED themselves were very new into the high-powered market. The LED’s were not very high performing and the optics were, frankly, worse. HID was still in vogue and so made the poor newcomers look very silly for distance. As they have evolved over the past decade both have improved massively but the original thought concept has stuck.
Following this train of thought then, flat country wants distance (with some width) and high country with lots of bends, twists and turns would benefit from a light bar. Study the manufacturers beam patterns, or better still, get in a vehicle with the lights you’re checking out and find out for yourself.
Vehicle
Even if we ignore the opening comments, there is some sense in fitting out a vehicle appropriately. As bull bars are not available for smaller SUV’s and passenger cars then a light bar on a nudge bar or number plate bar makes sense. On most full-size SUV’s and UTE’s there are umpteen bar options, all having the facility to fit driving lights or a light bar. For vehicles where the owner feels a nudge bar light is too red-neckish, then integrating a light bar in the front grill is now possible on most vehicles.
Personal preference
If you have enough width available for a 600-700mm light bar then this last point is really the decider no matter what your terrain is unless you desperately want 1 lux over 1km. If that’s the case then you’re best off with a pair of driving lights.
With so many vehicles having lights nowadays it’s very easy for you to get an idea of what you like the look of. Again, once you’ve decided on what sort of light to go for, research the options thoroughly. There is heaps of options at all ends of the price spectrum and unfortunately the retail price doesn’t guarantee you anything. Beam patterns are useful to give an idea but by far the best is to get your fitter or supplier to do a money-back option to ensure you’re comfortable with what you buy.
Why Buy an Australian Built Product?
Why does Ultra-Vision Manufacture in Australia?
What‘s Covered by Ultra-Vision’s Five Year Warranty?
Why do you need to worry about LED’s getting hot?
Most people think LED’s never fail, this is not true. A LED’s biggest threat is heat; this is why one of the greatest challenges in producing an LED lamp is thermal management (keeping the heat under control). LED’s also producing less light as they get hotter. LED Manufacturers typically measure the light produced by their LED’s after 25 milliseconds (ms). That is equivalent to a flash. It gives a Lumen number that is the absolute maximum value at the peak of the flash test. LED’s also generate a tremendous amount of power in a relatively small area. As the LED’s are powered for longer and longer periods of time, they typically get hotter and hotter depending on the thermal management system. It’s not unusual for LED’s to reach over 100 Degrees C. For vehicle or machinery applications, most specifications require that the lamp be measured at 10 minutes and 30 minutes to make sure that the LED Temperature has stabilised. This will result in the LED producing 10% -20% less light than its advertised value (this is taken into account with the effective lumens).
This is the reason for LED lamp housings are manufactured from aluminium (excellent thermal conductor) and feature large cooling fins. The aluminium housing and fins are just the beginning in transferring the heat away from the LED. Graphite pads, thermal paste, specialised circuitry and PCB boards also help in keeping the LED’s cool.
How do different LED’s vary in Light Output?
LED’s are available in a huge range wattages and sizes. Generally speaking the greater the wattage, the brighter the LED. This is not always correct and in some cases, some LED’s produce more lumens per watt. LED technology is advancing extremely fast, when LED’s first took the market by a storm they were producing about 80-90 lumens per watt. Now the new LED’s are producing up to 130 lumens per watt. This therefore means you are getting more light for less current draw. See below for more info on Lumens & Watts.
Whiter LED’s have higher lumen output than more yellow LED’s.
Some manufactures specialise in only high-power LED’s while others provide both high power & mid power LED’s.
Does an Optics Over the LED’s Reduce the Light Output?
As light travels through an object such as a lens, it loses intensity depending on the clarity of the material. This is due to inherent losses internal to the material and to losses as light travels from air through the lens back to air. These losses are present no matter the type of light. The losses associated with the lens material and optics can vary from 5% to 20%. An open optic lamp will produce higher effective lumens as the light doesn’t have to shine through anything, but the reflector of the open optic has to be precisely focused to get the maximum result from the LED. A dirty, scratched or dull lens or reflector will greatly affect the beam of light.
What is a Multi Surface Reflector & Why is it Better?
A Multi Surface Reflector or MSR is a reflector that spreads the light rather than relying on a lined lens over the front of the lamp to spread the light. An example of a lamp that features the MSR is the Quattro Elite driving light. A MSR reflector features very faint creases on the back of the lens, these are designed by using a special program to ensure the right shaped spread beam is achieved. Lamps with a lined lens produce less light, as the lens cuts back a huge amount of light output produced from the bulb. This can be likened to a light shining through opaque glass.
What Type of Optic or Reflector is Best for Driving Lights?
Well, good question and as you probably guessed the answer is: It depends… Covering applications as broad as driving, mining, sport, warehousing, housing, architecture etc there cannot be one right answer. What we’ve tried to do it hone done the three most common types found in the 4WD and mining industries, without attempting to comment on other forms or industries.
So, in simple terms there are 3 main types of optics used for driving lights, light bars and work lights:
All 3 have the application and are used in different applications depending on the complexity of the beam pattern, number of LED’s and other factors.
Reflectors
Ultra Vision mainly uses open reflectors for 4WD applications and is an open chromed pocket with a central LED. These are usually in a circular pattern for driving lights and linear for light bars. This style suits the driving light and light bar market where the beam pattern is requiring maximum output in a reasonably ‘simple’ beam pattern. The open form provides the maximum amount of output with only the lens detracting from it. In order to achieve this ‘simple’ beam pattern there is a serious amount of engineering going into the design to control the light in the best way. The chroming on the reflector is very important and a poor quality job here will nullify all the effort that has gone into the design. Quality control is therefore vital to ensure the performance is achieved that was expected. Having multiple, individual pockets of reflectance allows for some degree of variance. This gives the opportunity to have pencil and spread beams in one reflector and gives greater versatility for both driving lights and light bars.
Total Internal Reflection (TIR) optic
This type of optic allows designers to achieve very complicated beam patterns. The TIR is circular or square and locates directly on top of the LED on the circuit board. The LED shines into the back of the optic and the light is controlled by the internal reflection of the plastic. The critical element here after the initial design, is the quality of the tool making. A slight blemish or imperfection on the moulding tool will result in the light straying. Overall it is very effective and efficient if designed well and produced with high quality materials. All different plastics and polymers have different properties and so the optical performance is highly dependent on the quality control of raw materials. A significant benefit is that once tooling has been done for an optic, it can used in multiple arrays with other optics, giving further configurations without having to do new tooling each time.
Reflector with secondary optic
This method is commonly used in older or less expensive lighting systems and tends to be the least efficient of the 3 methods. There are inefficiencies in the reflector and TIR models and these tend to be compounded when put together. While it is no doubt possible to achieve goods results with this method the difficulty of aligning the LED, reflector and optic make it more challenging in assembly. Slight misalignment affects the results for each LED and when there are multiple LED’s this possibility increases. Also, like TIR the quality of the materials used is very important and can affect the results by 20% if not managed well. This is particular noticeable when long distance is being achieved like for driving lights, and not such an issue for a work light.
Conclusion
Like many of these discussions it comes down to the application. Is there a right or wrong. Not really because as far as we can see, every designer has their preference and expertise in a specific field, which influencers what works and what doesn’t. The main point is what the end result is and how this can be achieved in production. This is proved by the light patterns in a laboratory test, or more importantly, field tested on the road.
For the past few years our preference for driving lights is open reflectors but the flexibility of TIR is great for work lights. But with the way LED’s have evolved over the past 5 years, we certainly don’t know what’s going to be best in the future.
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