Concept
Glare Control
Vertical surfaces Type of reflections on flat surfaces
Veil luminance: Reflection caused by incorrect position of luminaire
0 In Io
P
P
C
C1
O1
Tilted surfaces Correct distribution between shiny surface and luminaire for good appreciation of contrasts on observed objects.
P
C
O2
O3
O4
P P
C1 O1
O1
C
C1
P
Avoiding reflections
One of the worst experiences in a gallery is when the view of a picture that is shiny or mounted behind glass is spoiled by a bright and glary image of a spotlight reflected in the glass. We must remember that in case of a reflecting surface the light is reflected with the same angle it reaches the surface with. To avoid reflections on artworks, one can carry out a test based on the law of specular reflection.
To do this graphically, first draw a line to represent the glossy surface of the painting. Mirror luminaire P into position P’ and connect P’ with the observer's eyes. If the line (P’O1) intersects the vertical line (which represents the wall) outside the yellow area (luminous flow of fixture) C1, the observer will see no veil luminance from that position. Therefore, the position of the fixture is correct.
In the figure, the position of the fixture with respect to observer O2, O3, O4 is correct. The position of observer O1 is correct, even if borderline. Reflections off the surfaces of glass cases can be equally annoying. Vertical glass surfaces can act as the picture described above. Angled surfaces can also create reflections, but the rules are the same.
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