I’m no expert on this but I’m sure one will come along, but 650 to 750 Lux seems quite high for the type of work being carried out. My understanding ( just checked the book) is that office environments should have a minimum of 320 Lux ( when I did some checking in our office where engineering drawings had to be studied, we had readings of 350 to 420 and was more than adequate and nobody had a problem ( about the only thing they didn’t have a problem with!). It also lists that high tolerance machine work at a bench should be 400 Lux and Electronic assembly or jewellery / watch repair 600 Lux. These are quoted as minimums, but you can see where this leads you.

Could you just have some of the bulbs / fittings removed in the questioned area, or some of them put on a separate switch? You may even save some money! If you think the 170mm makes a difference test it; go to the lower working area, put the meter on the desk and take a reading, then move it up 170mm and take another then compare. Not sure about the darkness thing, but I would guess that you have to test in worst case scenario to ensure minimum levels. It gets dark early this time of year. If you want to test in daylight and you don’t want the employees to know, go in on a non-working day or lunch time if they all go out (or if neither of these is possible, you could be really sneaky and do it in a fire drill).

If I were a cynical person, I might say your engineers sold you more lights than needed.

Hope this helps a bit

PS I guess I should warn you that my experience is over two years old and so considered by some as invalid and out of date.

Pats

As 'discomfort glare' is a psychophysical phenomenon, it consists of both physiological and psychological responses to physical and psychological stimuli.

The terms of your question appear to address the 'discomfort' as simply a physical phenomenon. By gathering relevant psychological data, you're likely to get quite a different set of responses.

Some good research on the work environment was published by social psychologists (sponsored partly by Rentokil) at Exeter University who demonstrated fairly convincingly how much social factors influence perceived levels of comfort as well as actual levels of performance. If you want me to trace the references, please pm me with a fuller account of the social environment of the workplace(s).

Another possible factor may be the frequency at which the fluorescent lights operate. The vast majority of such lights operate at 50 cycles per second (cps) due to the alternating nature of their mains power supply. According to studies, including one by the Medical Research Council (MRC) in the late 1980s, the oscillation/change of direction of light within a standard fluorescent tube is imperceptible to the human eye but is detectable by the human brain and can induce headaches, etc in some people. However, the MRC study found that when the frequency of the fluorescent lights in study premises were increased from 50 cps to something like 30,000 cps (and without employees in places being told) it was found that the adverse effects disappeared because the oscillations were no longer detectable by the human brains.

Apparently it shouldn't cost a significant amount to modify the relevant bit of an existing fluorescent light to sufficiently increase its operating frequency. Also, specifiers and installers of lighting apparently ought to know these aspects and discuss them with clients, but either don't know or don't bother. As I'm no expert in these matters, hopefully forum users with more knowledge and experience can comment on these points.

Also, switches with dimmer devices capable of controlling the brilliance of fluorescent lights are available nowadays. For example, the large open-plan office where I'm based has plenty of such switches, with the result that the lighting in several parts of the office is quite subdued presumably because most employees in those parts dislike full brightness. Nevertheless some of their colleagues find the levels too low and therefore use localised anglepoise type lamps to supplement the general fluorescent lighting which is available as downlighting and/or uplighting.

As some bright spark [semi-pun] might well ask if I know the operating frequency of the office lights, I'll admit that I don't at present - but could ask the local facilities management manager if he either knows or knows who to ask!