From the point of view of large surface area of reflected light and the desire for the light to come from above it is sensible to actually illuminate ceilings, even though there is no significant action taking place on the surface. This approach creates a very homogenous illumination, although care has to be taken to avoid too high a luminance, over 1500 candelas per square meter. Too high a luminance feels unnatural and can cause glare. In ideal case the cut-off angle of a luminaire is very small and therefore the shift from illuminated areas into dark is soft and gradual. Using an internal reflector and a diffuser is a good idea in this case.
LG7, the lighting guide for office spaces, takes ceiling illumination into account as well, unlike the EN 12464-1 standard. It is difficult to measure, but it can be achieved using a luminance meter and repeated measurements in different spots to get an average value. Such measuring, especially over a large area, can take several hours, but it can be done. It is necessary to do only once and can bring long-term beneficial effect stemming from a correct set-up of ceiling lighting system. A computer program can help calculate the effect of ceiling illumination.
LQS also goes beyond standards in demands for illuminance. Where norms see 30 or 50 lux as sufficient, we propose 75 lux as the new standard and a requirement to achieve the highest possible ranking in this category.