It is through the perception of contrasts that we see the world around us. Discrimination between objects and surfaces is the easier, the greater the contrast. Reflections on glossy paper, for example, can cause glare and greatly reduce contrast. This causes problems with discrimination.
A lighting system with good contrast rendition will present few if any problems with reflections. In addition to the finish of the objects or surfaces in the visual field, reflections depend on the incident angle of the light from the luminaires in the room, and on their luminous intensity und luminance.

Contrast rendering factor CRF

The loss of contrast deriving from reflected glare can be quantified with the help of the contrast rendering factor (CRF) (LiTG Publication No. 13, CIE 29/2). This is an expression of the relationship between contrast (C) for a standard visual task in agiven lighting situation and contrast (Cs) for the same visual task under reference lighting conditions.

Rough analysis

The relevant procedure in the planning phase is to superimpose a grid on the room (0.3 m x 0.3 m) for a rough analysis. The angle of vision is represented as a series of lines running parallel, transverse and at 45° to the axis of the room.

Detailed analysis

Once the most suitable areas for locating the workstations have been identified, they are subjected to a detailed analysis using a smaller-scale evaluation grid.