Calculating obtrusive light: Whose job is it? – April 2022 Newsletter

Obtrusive light. What is it and why are we increasingly being asked to calculate it? More to the point, why is it something that more manufacturers are being asked for. I mean . . . . what’s going on? Surely, that’s the job of the lighting designer. Isn’t it?

Whether as lighting designer, engineer, architect, or even client, you may well have been involved in exterior lighting projects.  You may have noticed that, apart from the aesthetic elements of what exterior lighting looks like, the last few years has seen increasing concerns around the impact of artificial light on our night-time environment. Put those concerns alongside the embarrassing reports about professional ability coming out of the Grenfell enquiry and we shouldn’t be surprised that competency is fully in the frame.

So, to the crux of the matter…

Obtrusive light (sometimes referred to as light pollution) is generally based around sky glow, glare, light spill and light intrusion. And it’s something that can be legislated for if it is deemed to be a ‘statuary nuisance’.  It doesn’t matter how good your design looks; it only takes one upheld complaint for the design to be challenged, revised and, in the worst-case scenario, turned off altogether.  There are standards that apply, their are local authority by-laws and more.

Maybe not so bad if it’s a neighbour who’s taken that flat-glass luminaire and decided that it works better when aimed up at 80 degrees; a polite conversation will often suffice, assuming that they are reasonable people, which they surely will be (?!?!) Though, thinking about it, don’t you just love looking out of your window into the face of someone else’s floodlight?

But ramp it up another level and it’s a different kettle of fish. Let’s consider a large commercial/industrial development, where serious money has been spent. Then we can look forward to one super-angry client and a cartoon cloud of dust as those involved make a run for the exit, because the next question will be who is going to pick up the the bill for sorting out the changes that are needed?

If you are working for a manufacturer it is more than likely that, should this situation occur, you’ll be asked (expected?) to pick up the tab. This situation risks becoming most pernicious, given that the manufacturer has usually worked from minimal information and has simply interpreted someone else’s layout. We all know how often site conditions differ from the purity of a nice CAD clean drawing, and it’s a massive assumption that whoever did the layout in the first place knew the whole story.

So what’s to be done ?

There seems to be a trend for manufacturers being asked to mop up problems, post-installation. Perhaps the client didn’t want to pay for the obtrusive light calculations, maybe because ‘the manufacturer can do it’ or ‘the contractor deemed it unnecessary’. But regardless of reason, it was a bad decision

So, who’s responsibility is it to get the job done properly? The client? The designer? The installer? It seems grossly unfair to expect the manufacturer to carry responsibility for something that they may not have had the full competencies to carry out, by which I mean that they are unlikely to have received all of the information required to provide the obtrusive lighting assessment. That’s the kind of information that can only be gleaned by a full site survey that no one wants to pay for.

And that’s the core of the problem. Unless we make our clients aware of this situation we can expect more of project failures – and, ultimately, less support from our manufacturing colleagues.

Obtrusive lighting calculations need to be carried out by those competent professionals (engineers and designers) who have all of the data required to properly assess the likely impact of an exterior scheme. They will be the people who are in a position to make a full survey of site conditions, the likely neighbouring conflict areas and a full understanding of how the lighting installation is intended to be used.

Lighting design is not well-served by design studios gaming the situation by promising a specification provided that the manufacturer provides an overview of the likely obtrusive light situation. That situation gets even more poor when the designer isn’t able to provide a full brief for the calculations. That’s where the incompetencies come from. And its simply not good enough.

This is getting a bit personal, but this is an example of what I’ve been faced with recently:

With our finger on the stuttering pulse of the jobbing lighting designer, the part of obtrusive light that has caused most conversation and angst amongst our community is the part that deals with limits of luminous intensity. Or, in plain English – the glare from the face of the projector. Its a calculation that can only be made when the designer knows where the observer is placed in the overall scene.

Essentially, it’s about the projected area of the product, which is affected by the difference caused by the viewer’s perspective, as the apparent projected area is different for each product seen from a single observer position. Perversely, it’s the one with the smallest projected area (or Ap) will give the greatest cause for concern.

The trusty workhorse of Dialux has yet to catch up with this aspect, as I found to my surprise (and displeasure) when recently working on an exterior facade.  I know of that can calculate it is AGI, which I found quite tiresome and expensive, although I did appreciate it telling me to ‘chill out’ on occasion.  Relux Desktop has an  add on program called KCalc which is specifically for the detailed calculation of obtrusive light, a must for anyone who does exterior or facade lighting design.

I was fortunate to have a good lighting friend (we all need those!)  to talk the problem through with, because a solution exists for the competent designer in GN01/21 from the ILP, with some worked examples. You can unknot your brow and head to pages 23,24 and 25 where the answer lies. Easy if you are a member of The Institution of Lighting Professionals.

The Principal´s Pen

The time merry-go-round never stops.  Here we are on 1 April 2022.  So much has happened in the world in the last 31 days.  Similarly, so much has happened in our businesses too.

It is quite amazing to reflect on our lighting design and projects business.  We have received more project work during the first two months of this year than we received throughout the previous almost two years during the various occasions and phases of lockdown through the pandemic.  New students continue to enroll.  Overseas institutions continue to recognize the quality, the high academic and practical value of our Advanced Diploma in Illumination Engineering course.

I continue to be most concerned by the fact that the application of lighting standards in South Africa is so poor.  After considerable research into this matter, the main cause for this situation is the lack of knowledge and understanding of each of the Standards, often coupled with staggering misinterpretation of those standards.

It is high time that professional architects, electrical consulting engineers, lighting designers, lighting companies and anyone involved in lighting design, purchased the highest international standards to apply to every project.  For example, SANS 10114-2: 2020: Interior Lighting: Part 2: Emergency Lighting fails to address battery emergency systems, the use of UPS and much more.  It also does not address the process of light measurement on emergency escape routes, emergency escape lighting testing, recovery, commissioning and handover.  To this end IS3217 is complete down to the smallest detail.

Webinars that I have presented on the subject of standards have been overwhelmingly attended by professionals from around the world but only a handful from South Africa apart from our students.  Is it because other professionals in South Africa believe that they know it all? Or is it simply apathy?

My students will be relieved to know that they will all be taught according to the highest international standards no matter where they live in the world.

The Student Support Sessions for First Year and for Second Year students are well attended.  As the students gain confidence and understand how they can benefit from asking questions or simply by listening to the questions asked by others and the discussion that follows.  I am confident that more students will attend in future.

Students continue to make use of private lessons to supplement their own studies and for preparation for the final examinations, for both First and Second Year examinations.

I wish you all a very good business month and trust that projects will continue to roll in for all of you.

With best wishes

We would like to welcome the following new students to BHA School of Lighting

  • Donovan Pentz, ALTSA, Johannesburg  – BHASL003C19: Advanced Diploma in Illumination Engineering Course
  • Lifa Madalane, Transnet National Ports Authority, Gqeberha – BHASL003C19: Advanced Diploma in Illumination Engineering Course
  • Livhlani Ralikhwata, Transnet National Ports Authority, Durban – BHASL003C19: Advanced Diploma in Illumination Engineering Course
  • Scelo Petrus Cele, Johannesburg – BHASL003C19: Advanced Diploma in Illumination Engineering Course

Happy Birthday to the following past & present students celebrating their Birthdays this month of April! We hope you all have a memorable day!

  • Anke De Wit, Windhoek, Namibia – 7 April
  • Warren Watt, Johannesburg – 8 April
  • Mark Walsh, Windhoek, Namibia – 8 April
  • Clint Davids, Cape Town – 11 April
  • Stuart Spooner, Johannesburg – 12 April
  • Robby Cohen, Cape Town – 16 April
  • Olga Timoshkova, Minsk, Belarus – 17 April
  • Mark Storm, Cape Town – 21 April
  • Bjorn Smidt-Hart, Benoni – 23 April
  • Leshmook Maharaj, Durban – 29 April

The following students are preparing to write their first year final theory and practical examinations before starting second year studies.  We wish you success!

  • Shaun Bergh – as you prepare for the first year practical examinations
  • Kubeshan Gopaul, Johannesburg – as you prepare for the first year practical examinations
  • Leshmook Maharaj, Durban – as you prepare for the first year practical examinations
  • Ruben Trigaardt, Cape Town – as you prepare for the first year practical examinations

Congratulations to the following students who have passed end of year examinations!

  • Armand Gouws on successfully completing his First Year Examinations
  • Scott Williamson on successfully completing his First Year Examinations

Upcoming Events from BHA School of Lighting


Cost: Free of Charge

Date: 21 April 2022

Time: 5:45pm for 6pm – 7pm (SAST)

Presenter: Phil Hammond

About: Over time, many of those who have attended previous webinars requested me to include certain topics in future webinars. Well, this is the first webinar that will cover a number of those topics some of which will include:

  • Lighting design philosophy
  • Lighting techniques
  • Factors to consider
  • WELL Certification
  • Designing for artificial light combined with natural daylight
  • Lighting for residential
  • Lighting of restaurants including Back-of-house (BOH)
  • Various applications such as office, education, retail, large industry, warehousing, and more
  • Lighting to cater for the disabled – wide spectrum of disabilities
  • Effects of glare

Events from the Institution of Lighting Professionals (The ILP) UK

NOTE:  ALL ILP STUDENT MEMBERS (BHA School of Lighting Students) free to register for the following events:

  • YLP (Young Light Professionals) event  6 April 2022 at 12:00 SAST
  • Highlights – 25 April 2022 at 14:00
  • How to be Brilliant – 24 April 2022 at 19:00 to 22:00 SAST



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