Interior lighting

Aim

In Part 6 of the DIN 5035 standard (Illumination using artificial light – Measurement and evaluation, at present under revision), it is fixed how relevant photometric quantities have to be measured. In comparison with the recording of single measuring values by means of devices measuring point by point, image-resolving measuring devices can measure complete scenes using one single capture (many thousand measuring values). In addition, those measuring devices are able to take geometrical parameters (angles, solid angles) into account from a metrological point of view, which permits the user to determine not only the luminance prevailing in the scene captured, but also any derived quantities.
Thus, for example for determining glare values, it is important to ascertain not only the luminance of the glare source, but also its apparent size (solid angle) as well as its angle to the direction of sight.

Büroszene

Measurement of the veiling luminance

The equivalent veiling luminance is defined by the illuminances caused by the glare sources on the eye with a direction-dependent weighting.

Often n = 2 is used, with other evaluation functions being applied occasionally. In principle, the veiling luminance results to:

The illuminance on the eye can be obtained from the measuring data of the LMK by simple computational manipulations using the functions offered by the LMK 2000 software.

Glare evaluation using UGR

The glare evaluation of illumination scenes according to UGR also requires the measurement/evaluation of photometric and geometrical quantities. The measuring parameters (luminance as a function of the direction and solid angles) can be measured by means of the image-resolving LMK camera.
The surrounding luminance L_u can be determined through averaging over the whole data record. The glare sources L_i can be defined and recorded via luminance thresholds. The appertaining azimuth and the solid angles of the glare sources result from the geometrical data measured in the luminance image and from the parameters of the measuring system (linear magnification for solid angles) as well as from its position in the room.