Controlling Glare

The light that we see can be thought of as the light that is leaving its source or light that is being reflected off ours surface. The lighting can be both direct or indirect. For this reason while it is a good starting point to know the wattage of a fixture, the final output is often different depending on how much lighter is falling directly and indirectly on a surface. This level of light on an object is measured candelas/square metre, although some English texts refer to it as footlamberts.

At the risk of sounding ridiculous, what is brightness for? Of course it is suitable for a variety of purposes. A sudden brightness can create a sense of drama. If you’ve ever watched singing competitions, sometimes someone happens to be doing a song, that builds up during the bridge – what happens before the final chorus? The light suddenly falls on the gospel choir that had been standing in the wings and as they join in, the effect is uplifting. But imagine if you heard them but there was no light on them. The effect would be totally lost.

Focussed beams can create sparkle and glitter elements in a space. If you’ve ever watched a play in the theatre and perhaps someone picks up a shiny ring, for example, how is the shine of the ring picked up? By focusing a direct light to illuminate it. But likewise the effect of seeing a focused light is magical, instead of having to make believe in the mind.

But brightness itself must be controlled and managed. High levels of brightness can produce glare which is uncomfortable or after prolonged periods, cause impairment. To complicate matters, glare can be directed, or reflected, so brightness projection from all angles needs to be considered.

Direct glare comes straight from the light source. In a theatre, an incorrectly sited light from the back or side of the stage can shine directly onto members of the audience.

Reflected glare is glare resulting from indirect lighting deflected back to the viewer. The lighting falls on the task itself, such as reflected glare from a screen.

Like direct glare, reflected glare can also be sub divided into two categories, discomfort glare and disability glare. Discomfort glare makes perception uncomfortable while – as the name suggests – disability glare causes impairment.

The same surface can cause different types of glare.

For example, a bright mobile phone screen gives direct glare if you look at it in a dark room. In the day, if light reflects of it, it causes discomfort glare.

There are many ways to prevent unwanted glare. One common method is to use indirect lighting, which focuses more light upward than downward. This means the resulting light has reflected off the ceiling and is easier on the eyes. It minimises the glare on lower surfaces such as computer screens.

Fixtures that also incorporate diffusers such as glass so that the output of the light is scattered.

In workplace conditions, the general background lighting can be minimised so the overall lighting is not too bright and in areas where a brighter lighting is required, local focused light in the form of adjustable task fixtures can be implemented.

Other simpler solutions include moving the light source to a different position or changing the angle until glare is removed.

The reflection of the work can be altered to absorb light if required. How can it be altered? You don’t need to start ripping up work tops, just a simple coat of paint or a less reflective cover would do.

If the source of glare is natural lighting, use blinds or shades to either block out light or adjust the angle of incoming sunlight.

Too much glare causes discomfort and prolonged exposure would cause a reduction in the quality of health of those who have to live and work under that kind of lighting. Imagine if you had to live under glare for eight hours a day, as you would in an office during the darker months. A knowledge of lighting principles would go a long way in making your work more comfortable and give you a better overall quality of health!

Lighting Books and Reviews

Set Lighting Technician’s Handbook: Film Lighting Equipment, Practice, and Electrical Distribution

Comprehensive. Detailed. Practical. Set Lighting Technician’s Handbook, Fourth Edition, is a friendly, hands-on manual covering the day-to-day practices, equipment, and tricks of the trade essential to anyone doing motion picture lighting, including the lamp operator, rigging crew, gaffer, best boy, or director of photography. This handbook offers a wealth of practical technical information, useful techniques, as well as aesthetic discussions.

Review
“Harry Box’s Set Lighting Technician’s Handbook (Focal Press) is a gold mine of information about safety, lighting and studio procedures.” – Ron Dexter, ASC

Harry C. Box has worked in television and motion picture production since 1989. Over the years he has done substantial work as a lighting technician, gaffer, camera operator, director of photography, and as an educator. His recent credits include network and cable television series, such as Heroes (NBC), Brothers and Sisters (ABC), and Everybody Hates Chris (CW). He has worked on major motion pictures, independent feature films, telefilms, documentaries, music videos, commercials, and industrials.

I’ve had previous editions of this book and like to pass on the old one when I upgrade. This, the 4th edition is presented extremely well, is bang up to date and is indispensable. The best thing about this book is the lack of an opinion which plagues a lot of cinematography books, this is simply the tools, how they work, why you would use them and that’s it. You apply your current project needs to this information and develop your own technique.

If you are an aspiring electrician and want to work in movies and commercials this is a must-have for your shelf. Even a seasoned pro can learn a thing or two and the attention (and clear explanation) given to electrics is superior to any trade manual on the market. I’ve been reading, Mr. Box’s articles in Film Crew Magazine for the past few years and it is even more valuable to be able to have some of this knowlege bound in a book.

As a long time theatrical technician I found the book to be very insightfull as to the practices of film lighting world. I wish a book this good was written for stage hands. It is a practical guide to the film lighting business with not just basic information but tips to make you feel like on old pro. After reading it I would feel comfortable taking a work call on a film set any time.

A great book for any film electrician, whether you’re starting out or need a handy reference for wiring anything. It gives overviews for every aspect of lighting, starting out with the types of lights and cables and going into electrical theory later on. This book has basically become a must in the IA local here. This is a thorough, detailed and comprehensive handbook, with a wealth of useful information on equipment, techniques, and practices. A great source of insight and inspiration.

Studio Photography and Lighting: Art and Techniques

This book gives clear, practical advice on how to get creative with and achieve the best from your studio lighting. It explains and demonstrates basic and advanced techniques so you can fully understand how to light a subject and compose a great photograph. Explains lighting and camera techniques and the ideas behind them. Utilizes specific examples and diagrams to illustrate everything from portraits and art-nudes to still life photography.

Christian Hough is a professional photographer. His polished commercial and fine-art nude photographs are synonymous with exquisite lighting and impeccable technique.

It’s filled with some excellent portrait photography and also a description of how to achieve that photo, along with diagrams and settings. Easy to read, lots of tips for beginner, enthusiast and professional alike.

A very useful reference book if like me, you are a photographer that rarely ventures into a studio. It is clearly laid out and written in understandable English. It has given me the confidence to use a studio and be able to explain to a Technical Support Worker at University exactly how I want the lighting set up for my shoots.

Has pride of place on my bookshelf next to my camera manuals notebooks. Also helpful in working out how images have been lit so you can try it yourself if you want to. I find it useful in helping me to understand more about lighting and getting more from my own photography. It is not a definitive all encompassing everything you will ever want to know manual, but it’s a great start and I suspect it will be my go to reference book for quite some time, well worth buying and I may get the Kindle version for my Fire Tablet.

So glad I bought this book! Other volumes I have studied, just swamped me with high-cost “options”. Just the sort of insight I needed, for my first steps into studio work and simple set-ups. If you are at the threshold, like me, this book will help demystify so much superior jargon that’s out there.

Light Metrics – Quality of Light

We pick up impressions of things around us largely through visual means. Scientists have estimated that as much as 85% of human impressions are derived visually. This figure might seem unnaturally high, but if you think about it, your eyes are the medium primarily through which information is first received. The exception to the rule is for people who are visually impaired, and who hence rely on other senses. Because the eyes are first to perceive the things around us,  proper quantity and quality of light are essential. This is what lighting aims to achieve. The mission of lighting management is to give optimum level of lighting, a quality of light, and all this achieved at the lowest cost. This compromise of variables is what we have examined in the previous post on architectural lighting.

When lighting engineers speak of and discuss lighting, there must of course be variables that are commonly defined in order to be specific about the level of lighting required. Otherwise discussions would only include subjective terms which are not helpful to the task. If someone told you they wanted a stage to be brightly lit, their idea of bright may not be the same as yours. And if you arranged for a stage to be lit as how you felt bright was, the probability that you would be in concordance with their wishes would be fairly slim. Or if you ordered a lighting fixture but could not give any specific details other than that you wanted it to be bright, it would likely leave your supplier flustered in trying to obtain more specific details, or you might be presented with a whole list of items while the supplier goes “Like this one? Or maybe similar to that one?”

To use another analogy, if you were trying to cook a meal, and were seeking details such as the kind of heat – low, medium or high – and the duration of heat, but if you were told “Hot, just make it hot” then this would be completely befuddling.

So we need lighting metrics.

We use lighting metrics to discuss and the quantity of light (light output and light levels), quality of light (brightness and color), and fixture efficiency (electrical efficiency and how much light leaves the fixture).

The rest of this article will address the first metric, which is the quantity of light.

The quantity of light that leaves the lamp, or the light output, is called the luminous flux. The luminous flux is measured in lumens (lm). Lamps are rated in both initial and mean lumens.

Initial lumens is the measurement of how much light is produced by only when the lamp is deemed to have stabilised. The stabilisation period for fluorescent and high-intensity discharge (HID) lamps can usually last for 100 hours
The other measurement, mean  lumens, is the average light output over the lamp’s rated life. A lamp does not last forever nor does it produce light constantly at the same quality. A number of factors affect a lamp’s light output over time. The mean lumens is general works out to be 40% of the rated life.

The output of a fixture can be affected by the diminishing quality of a bulb. It can also be affected by other factors such as the characteristics of the fixture itself, such as its reflective quality, and hence is susceptible to fixture surface depreciation, and dirt and dust buildup.

Illuminance, or light level measures the amount of light on the workplane in the lighted space. Illuminance is assessed using the unit footcandles (fc) (or lux in metric). A footcandle is actually one lumen of light density per square foot. If you are using metric units then one lux is one lumen per square meter.

  • The human eye can adjust to a wide range of light levels, including about 10,000 footcandles on a sunny day to about 0.01 footcandles under full moonlight. Despite the variation of range, optimum ranges of light levels have been established for various tasks so that those tasks are performed most efficiently and without strain.

Architectural lighting considerations

Architectural lighting design is much like architecture itself. It requires a combination and understanding of both artistic and scientific aspects. How do what are supposedly two differing worlds work together? It would not be an assumption to state that the science has to support the artistic. Architectural lighting is about using the knowledge of the scientific to bring out the aesthetic.

Look at it this way. As far as lighting is concerned, the end effect is apparent. Someone may say “I want this section to look bright while the background is lit with red sparkles.” What is not so clear, and this is where a lighting engineer can bring in knowledge, experience and expertise, is how this effect is going to be achieved. The lighting engineer can bring in years of training and know-how, and for the beginner, having the lighting engineer to learn from can take years off the learning curve and process is accelerated.

A creative spirit is sought from a lighting designer. But it is not all about creativity. The qualified professional knows how light works, understands its properties as well as its effects on humans. He knows the aesthetic impact of light on humans.

Too much light? It causes glare and causes discomfort. Too little light also causes discomfort, but in a different way. If you have to squint to narrow your focus because the lights are too bright, your body language is immediately defensive. If the lighting is insufficient and too dark, you have to psychologically extend yourself in order to make more sense of it. An object with higher level of light stands out from its background, of course, but how do you manage the level of overall light?

When it comes to architectural lighting design, the points of emphasis revolve around three areas of focus. These three areas are fundamental aspects that we will commonly encounter in the illumination of buildings and spaces. The aesthetic appeal of a building, how the building looks, is one of these. The second is what we might call the ergonomics, this is an aesthetic measurement of the lighting and its impact is experienced by the building/space. The third aspect is that of energy efficiency. If a lighting for a building scores well in all these three aspects then it is likely that its overall feel is good. Quite often the decisions a lighting engineer has to make are how to obtain a balance between all three even if there was one area he could really go all out on. There is no point excelling in two areas if the third average, because the aesthetic quality, the feel of things just wouldn’t be right.

The lighting designer often works in conjunction with the architect to arrive at a common consensus about the effect of the lighting. When it comes to aesthetic appeal, the architect’s vision for the project comes into play, and it is important for the architect to fully describe what he aims to get from the project. What parts of the building or installation does he want to emphasise? Which parts does he want to make more subtle? More importantly, what is the aesthetic, or the emotion, that the architect wants to project? The lighting designer has to fully take in the architect’s ideas and vision, and then work out the means to achieve these. The architect provides the “What” and the lighting designer provides the “How”.

The ergonomics of the design must also be considered. If it is going to be a brightly-lit space, will there be too much light for users during different periods of the day? And what about the changing of the seasons? Considerations for human users as well as the impact of the lighting on the surroundings must be factored.

To give a recent example, a company decided to revamp the entrance grounds, where all visitors and staff pass through. This involved the construction of a bronze company logo, which at night was highlighted by spot lights from various angles and backlit by semi-indirect lighting. The aesthetic the company sought to promote was that of pioneering leadership in its field, and the lighting brought this out fully. Visitors passing by in the night could see the logo well-distinguished from its surroundings. The only problem was that as winter approached and it got dark towards the end of office hours, those working on the ground floor were often blinded by some of the spotlights. If you were waiting in the lobby to see a member of staff, some of the lights, as well as the reflections off the structure, depending on where you sat, you might have well been sitting on a sofa with a red dot between your eyes.

Another company had the same intention, with their company logo of a torch on the grounds. At the top where one would expect to see the flames, there were four strong spotlights that streaked out to the sky to mimic the same effect. At the time of construction, at the start of summer, the project opened with the usual fanfare that accompanies such openings. But by late autumn no one was applauding, especially those who worked on the upper floors and fell in the direct line of the spotlights. Eventually it was decided that the lights would only come on after office hours, but in doing so, the aesthetic quality that the company sought to convey, that of being a shining light among its surroundings, was lost.

Ergonomics and aesthetics must be balanced and quite often ergonomics triumphs.

The third factor is that of energy efficiency. Even if the ergonomics and aesthetic aspects are satisfied, what is the cost of maintaining such lighting? It is no good having a well-lit installation if it is going to drain the company budget and be a source of future grumblings and spawn areas of contention. The running costs of the lighting are not only the costs that lighting designers have to deal with; they may have to find ways to source materials that accomplish the same effect but which do not cost as much to acquire or do not have high running costs.

The lighting designer has to find a way of meeting all the above three areas in a “best fit” situation – it is not point excelling in two and dwindling in the other. A project that is ergonomic, projects the desired effect but costs too much to run is no good. One that falls within budget, and projects the sought impression, but makes the surroundings or the nearby users uncomfortable is similarly an undesirable outcome.

Designers also have other considerations too. For more complex works, they have to project manage the work itself as well as the acquisition of building materials. They also have to evaluate the materials for cost and regulations, while also ensuring the outcomes adhere to building and energy codes. In addition, growing environmental focus has meant that they are increasingly under pressure to work sustainably – to source sustainable materials and deliver carbon-neutral works.

If it were a musical world, we would say lighting designers are the conductors and the orchestral managers at the same time. Not only do they have to conduct the various forces at the disposal to obtain a desired emotional effect, they have to recruit the musicians at the same time. If musicians are unavailable, they have to recruit others in their place, or find a way to get the same musical result without them altogether. And they have to make sure the budget for musicians is met. So if – at the start of this paragraph – you thought, “What an overstatement”, it really is not!

But one thing is for sure. In having to meet all these demands, it takes skill.

 

 

Recreating natural outdoor lighting indoors

The main areas when it comes to lighting are arguably indoor, outdoor, architectural and stage.

Indoor lighting concerns all aspects of interior lighting – how to frame residential, work or play spaces for the purposes sought from them, balanced with the economics of cost. Outdoor lighting is generally cheaper in terms of fixtures because the lighting requirements are more easier to define, and obstacles such as shadows and glare are less on an issue than they would be in indoor lighting, but more expensive in terms of electricity because the electrical demands to light an outdoor area are generally greater.

Architectural lighting is the use of light to highlight building features. Lighting is used to accent or soften lines so that the features of the building are prominently displayed. However, architectural lighting may not exist all year round, and may be seasonal or limited to special occasions or festivals.

Stage lighting is usually more of a frequent occurrence as it is a requirement in indoor entertainment, whether or not it takes place during the day. However it is not always accorded the importance it deserves because the lighting is usually secondary to the event. “Come hear the Arctic Monkeys play. A great theatrical event of sound and light” is the possible description of any similar event. Unless it happens to be music groups such as Gorillaz, who are renowned for their music as well as use of light, stage engineers often have to live with a two-line mention of their skills in a three column review the next day and be content with that.

Despite its relative anonymity, apart from the recognition from those in the entertainment industry, stage lighting requires technical skills and adaptability. A stage engineer needs not just to have the skills to achieve the desired effects required on stage, but a sense of awareness to know the perfect timing. Imagine a play on stage; the lighting engineer needs not just to know the requirements of the particular scene, but the script itself, so that the light can be adjusted according to how the scene develops.

Lighting is an important skill that we often take for granted. It requires not only prior planning but in-performance adjustment and fine-tuning.

In preparation for an event that requires stage lighting, the list of equipment required can be more focused if a lighting design is first completed. The lighting design is a simple diagram of the stage with physical objects marked out, and then with this in mind the lighting and the necessary equipment can then be selected to meet this design.

Simple enough? For starters, yes. But then, it is how you select the equipment to meet this design that show off your technical knowledge of the physical aspects of the equipment, your knowledge of the basic theories of stage lighting, as well as your experience as a lighting engineer.

In an indoor event, the lighting present has been selected and arranged in a fashion that mimics the natural lighting around us. The two main sources of natural light are the sun; and during the night, the moon when it reflects the sun’s light back to us. There are natural highlights and shadows created by this natural lighting around us that we have to account for on stage, in order to make it appear natural.

Think of it another way. The things we see around us all slant to meet at a point in the distance and if we do not account for this perspective when we are drawing a scene, everything will look two-dimensional, flat, artificial and unnatural. And when we are exposed to this unnatural shift for prolonged periods we eventually lose interest. It is the same with lighting.

While people consider lighting merely as projecting light onto a surface, if we do not account for the naturally occurring shadows and highlights, it is very tiring on the eyes and the mind, which has to subconsciously make a correction. Imagine you are watching a play on the stage, such as Romeo and Juliet, at it is the balcony scene where Juliet tells us “a rose by any other name is still a rose”. If we are led to believe the moon is on the left on the stage and Juliet is on the right, it would be pretty disconcerting if Romeo’s shadow fell the wrong way, towards the moon, due to a poorly-placed light. This would detract from the scene and all other things such as the words, the mood and any music that might be heard, and influence our opinion of the overall production, especially if the error arose again.

Proper, natural light levels have an influence on the audience’s mood and receptivity. It maintains longer eye and audio contact, keeping the audience’s attention more focused. Imagine someone making a speech but the general background lighting being brighter than the local lighting. In other words, when you look at the speaker, there is glare which detracts from the message, causes you physical discomfort and affects how your react to the message.

We might not realise this but when we are out and about during the day, we take in the nuances of natural lighting, the shadows and highlights as the light bounces off objects. It is this effect that we have to try to recreate indoors.

In the northern hemisphere, the sun strikes the earth at a relative 45 degree angle; this angle produces specific highlights and shadows.

The extreme intensity of the sun creates a strong highlight on one side of a three-dimensional surface and strong shadows on the remaining areas. But because the sun is so intense, a primary object is also slightly coloured by reflected light from, and of the colour of, other objects around it. This reflected light also fills in the shadows on the remaining sides of the object.

It would be easy to simulate the sun light, shadows and natural lighting effects indoors if there was some kind of lighting fixture that was of the same light intensity as the sun, but unfortunately we do not.

The moon provides a similar source and angle of light, but because the moonlight is reflected sunlight, it is less intense. The sun is rather like an uplighter and the moon is it’s ceiling. The lower intensity of light means that moon light does not create the same bounce or fill effect. Nevertheless, it does present its own set of difficulties because night lighting has much more contrast than daytime lighting. Yes, there are shadows, but not all shadows are the same. Not to a light engineer anyway. There are different grades of shadows which must be achieved in balance. Similar to the previous example, any anomaly will be picked up by the mind and may grow to become a distraction that disrupts the whole event.

To re-create the effect of natural lighting, multiple lights are required to achieve the same effect using the same principles. The minimum number of lights required is three, although the more options you provide, the more specific your lighting can be.

The basic three light lighting design would consists of one fixture placed at a 45-degree angle above and 45 degrees to the left. The second fixture would be at the same 45-degree angle above and to the other side. A third light would be angled at sharp angle to the rear, or directly downwards. There are hence three lights on the objects on the stage. The main light is known as the key light while the rest are fill lights. Each fixture may perform the function of the key light or the fill lights, depending on perspective.

This three-light method allows enough coverage of the stage to provide lighting to an object and lights to fill in the shadow. There is however a blind spot at the rear but it is not necessary to site a light there because to do so would mean the light would be shining direct at the audience, at the audience would be looking direct at the back and dark shadow of an object or person.

The 45-degree angle rule that the lights are arranged in is not set in stone but one should be mindful of using too extreme angles. The key of course is that lighting has to look natural and simulate what we see in daily life. Too flat an angle will create a shadowless light on the object, which make it appear almost flat, two-dimensional and generally uninteresting and a kind of lighting pattern the eye is not used to seeing. But sometimes this distortion can be exploited to suit an effect. For example, in a horror scene, a face can be lit from below, causing an unnatural look which creates the sense of unease that is being sought.

In a play, the night scenes use the same siting of lights as the day scenes as the moon creates the same angle of light as the sun. Using the same set up also ensures that there is no discontinuity in light siting throughout the play. However, as the light of the moon is reflected from the sun, the lighting should be less intense in a night scene than it would be in a day scene.

The three light siting works for one direction of viewing, that is, if you are watching from the front. If the seating pattern is different, such as on three sides of a platform, than the three light creates a blind spot that is visible to viewers from the sides. Hence, additional lights may be needed so as to recreate the same lighting pattern for those viewers. It may be necessary to incorporate a four-light lighting system that utilises two key lights and two fill lights.

Can you imagine what plays or music performances were like in the days before electric lighting? In the Baroque period, for example, composers like Bach and Handel wrote music for performance on a fairly frequent basis in courts? Musicians did not have any lighting apart from candlelight, and while it may have been disconcerting for them, spare a thought for the audience who had to stare for hours at flickering shadows that the candles created, while staring at the direct lighting of torches around a stage. In other words, to view a performance where the general lighting was stronger than the local lighting, and lots of shadows were created. In today’s concert world that form of stage lighting would have been considered wrong! And if that were not bad enough, they had to aurally focus on music that was contrapuntal in nature, with ideas passed on from one melodic instrument or voice to another, one which required a lot of mental focus. Watching a music performance must have been an arduous task then!

About Me:
I give piano lessons in Crouch End (London N8). Lighting is one of my many interests.

Want to know more about the Baroque period and the kind of music performed then? You can find out more about it from my other site.

 

Different Types of Lighting

Do we even need to debate the importance of light in our lives? Imagine the earth without the sun, which gives it light and heat. A warm summer’s day is one of life’s pleasures, and even in winter when the warmth of the sun may not be as apparent, the light it delivers gives us some inner comfort. If all that sounds too far fetched, then imagine yourself in a dark room. While it may be initially be calm and peaceful, after a prolonged period a sense of isolation creeps in and the eerieness becomes disturbing and the mind starts to play tricks on you. For this reason prisoners of war are often keeps in prolonged periods in dark rooms – lack of light is a form of torture.

Of course, too much light can also be a  problem. It forces us to narrow our vision to filter out the excess light, and the tension we can feel in our face is not a pleasant experience. When the car driving towards you has its headlights on full power we wince at the thoughtlessness. Too much light also strains the eyes. Remember the advice not to look directly into the sun? Or when you are looking at your phone in the dark at night? What we need is optimum lighting to serve the functions we require it for.

There are many categories we can discuss light in terms of. These categories and divisions help us to distinguish between the functions and characteristics of the different types of light in order to help us determine what we need. Lighting in general can be divided into the categories of indoor and outdoor lighting. Lighting can also be divided into the categories of local lighting and general lighting. Local lighting refers to light at a specific area, while general lighting refers to what is perhaps referred to as background or non-specific lighting. These four categories may have a degree of overlap to them. Are these divisions necessary? Definitely. You speak of a table lamp as a kind of indoor lighting where the local light is more powerful than the general lighting. The lighting you need indoors in the kitchen may be a mixture of focused and non-focused lights where the strength of local and general lighting vary. If you are looking for an outdoor light where the local illumination is stronger than the general one, then it is assumed you will be looking for a spotlight or searchlight. Knowing these categories help us to determine and discuss lighting needs with more clarity.

Whatever our lighting needs, we need to consider how direct or indirect the lighting is. The amount of light to an area can be wholly direct or wholly indirect, or a combination of the two. Even when used in combination, there are terms to distinguish between the different levels of combination.

Direct lighting is lighting where most or all of the source light falls onto the object. Reflecting surfaces have little or no effect at all. This system is perceived as efficient but you may get issues such as shadows if the lighting source is not sited correctly. A traditional table lamp is an example of this kind of direct lighting. Because the lighting is direct, prolonged exposure can also be very taxing. Even if you are not looking at it directly, reflection of the light by surrounding surfaces can be very strenuous on the viewer. If you shine a direct light into a reflective surface, for example, a table lamp onto a laptop screen, it is not good for your eyes in the long term.

Another type of lighting is diffused lighting. Diffused lighting is different in the way that most of the light to the object is broken up. The direct focus of the light onto an object is not present, but the lighting is ambient, broken up, softer, and kinder on the eyes. For this reason diffused lighting is used in certain residential settings to give an impression of warmth.

Another method of lighting is indirect lighting. This kind of method means that none of the source light falls directly onto the object or area. Instead, it is directed upwards and the surfaces reflect the light downwards or away. Indirect lighting is useful in avoiding glare, however it can make huge electrical demands because the light arrives indirectly as a secondary source via reflection.

Sometimes lighting demands are best achieved using a combination of lighting methods. These are termed semi-direct or semi-indirect methods of lighting. In both methods, light to an area is both by direct and indirect means, but semi-direct lighting has a greater proportion of direct light while the reverse is true of semi-indirect lighting. An uplighter may be an example of such combination lighting, and whether it is classed as semi-direct or semi-indirect depends on how transparent or translucent the material itself is. If it is entirely dark and does not allow light to pass through, then it would be lighting the room by indirect methods.

    

The different kinds of lighting methods are not specifically constrained to different objects; as we have seen before, an uplighter may either light a room semi-directly, semi-indirectly or indirectly. A bulb may light a room directly or it may do so doing in a diffused way.

We speak of lighting as being suited for indoor or outdoor purposes. Whatever the purpose, there are required differences in intensity between local specific areas and general areas, and there are different ways to achieve the desired level of light, using direct, diffused, indirect or combination lighting.

Imagine you are watching a classical music concert. There is a soloist playing the piano while the members of the orchestra are around him. The conductor stands in the front center. How do you light up the stage? The local lighting demands for the pianist and conductor are greater than the general lighting. But you can’t just focus a spotlight directly on the two individuals because the reflection of light from the piano might deflect the sharp glare back to the audience. And while a spotlight may bring out the conductor to the audience, it might also cast a huge shadow over the string players, especially the viola section. And in the course of the performance, various members of the orchestra may have solo sections of music to play and the light must fall subtly on them such that the audience can pick out who is playing. And over the course of the performance the lighting must adjust in intensity, the general lighting to an area decreasing slightly as local lighting increases slightly in a complex interplay, or the audience will have a headache if the level of light is too much. The length of the performance can also be an issue to consider when it comes to measuring the lighting intensity. So lighting is a complex task that engineers don’t get enough credit for – one thing for sure though; it is not just some guy turning lights on and off!

 

About Me: I give home piano lessons in Crouch End, London N8. For a post related to lighting on my other blog click here.