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The angle of light emission of a
luminaire: how does it affect us?
The amount of light reaching an object by means of a lamp reflector
depends on the opening angle. Also, the object stands out against its
surroundings when it receives greater quantities of light.
There are two attributes which help us choose an opening angle: the size
of the object which we intend to illuminate and its distance from the light
source.
The bigger the size of the object to be illuminated, the wider the opening
angle required. On the other hand, the greater the object’s distance from
the light source, the narrower the opening angle needed for illuminating it.
The opening angles are always defined by whole numbers. When a value
of an opening angle is ranged between 13º and 50º, we round the number
up to express it as multiples of 5, for example:
22º must be rounded down to 20º. For angle values greater than 50º, the
rounding is carried out to express the numbers as multiples of 10.
It is also important to consider the possibility of two lamps of the same
type, with both having the same power but different opening angles. The
lamp with a wider opening angle will illuminate an object with less light
intensity when compared to the lamp with a narrower opening angle.
We must take into consideration the global energy savings stemming from
using light efficiently; when we optimise the use of light we avoid light
saturation (flat images) and therefore we gain a more realistic perception
of the true volume of objects.
Basic lighting concepts
