when a recommended lux level in a room is say 500, from where do you measure this?

Question

I am supposed to reach a lux level of 750 in a room.

I have chandeliers and downlights installed.

Depending on where you are in the room, whether you are standing or sitting down; where do they mean when they say - recommended lux level is 750, does that mean right below the light, at desk level, standing right below a downlight, average light in the room?

if you know, pls inform me.

thanks

Answer 1

This is an average illumination, which should be measured on the working plane.
The working plane is that height above the ground where the major tasks in that room are undertaken.
i.e. in a workshop, probably at 900mm Above finished floor level.
in an Office at say 750mm AFFL,
In a corridor this would be at floor level.
To measure the average illumination, one should take a number of measurements, with a luxmeter, on a measured grid, across the entire width and length of the working plane. An average should be obtained from these readings.
Remember to adjust the readings if necessary to suit the types of lamps.
It is usually applied with Uniformity which is expressed as a percentage i.e 70 %.
Uniformity is the ratio of minimum illumination to average illumination, such that the intent is to provide an even level across the working plane. There is usually a 'buffer' zone to a 500mm or so strip around the room, which is an area usually considered very difficult to uniformly illuminate, and also outside the working plane.
If you were trying to light a room to 500 lux with Uniformity of 70 %, then the lowest level of illumination should only be 350 lux minimum (Or as a percentage of the actual average measured.)
You mention that you are trying to light a room with chandeliers and downlights to 750 lux, and I would question this. Typical rooms which use these type of luminaires do not normally require such high levels of illumination.
Typically a dining hall / conference room would only be about 300 lux.
Offices are typically 350 - 500 lux.
Corridors are 100 - 150 lux.
Entrance halls may be about 200 lux.
Hope this helps.

Answer 2

The normal Lux level for and office etc. is taken at the working plane whereas open areas are taken at the floor level.
750 Lux seems very bright to me, the normal is 300 - 400Lux
for reading and writing.
There are a host of other requirements linked to lighting design.
Glare, LG7 (in the UK), CIBSE recommendations, Ilumination, reflectance and colour of the room surfaces.
You could try looking at a lighting manufacturers web site to try and download thier design software.
Putting lights up commercially is not just a case of visiting the local lighting shop and choosing what looks nice.

Answer 3

500 Lux

Answer 4

If it were an office, you would have to have the recommended illumination on every working surface (desk).
If it's not an office (or anything like that), then I'm not aware of any specification. These might even vary from country to country! So what you should do is to ask the authority that recommends this level of illumination how you have to calculate it.

Answer 5

It is measure at desk height 29inches.

Answer 6

average level