Current
Electrical charge flux (usually negative) passing through a surface during a time unit.
It is a fundamental magnitude in the International System. It is measured in Ampere.
Cut of
In a photometric solid, it is the angle or the angles in which a net distinction between
light and dark can be perceived. It is calculated in respect to the main axis of the device.
D
DALI
Digital Addressable Lighting Interface. Protocol managing a system of light fittings
through a signal transmitted by a single pair of wires. The DALI system can manage
single or groups of light fittings included in the same system. Also, it can switch on
and off and create scenaries with light fittings belonging to a same system.
DALI-SwitchDim
Compactibility of the power supply to work on a DALI protocol only or also through
the SwitchDim function. In this last case, the load dimming is made through a simple
push-to-make switch at the supply voltage.
Dark light
Device showing a luminance lower than 3,000 cd/m2 in every ‘C’ plan for ‘gamma’
values equals or higher than 65⁰. It is calculated in respect to the main axis of the
device. This value was originally 1,000 cd/m2, now it is increased to 3,000 cd/m2 for
most devices.
Dialux
Light design software. Used to obtain all types of lighting calculations and related
documentation in accordance with the legal regulations in force in various countries,
as well as visualisations and animations for a realistic rendering of a project.
Diaphragm
Element modulating the amount of luminous flux passing through an optic system. A
so called ‘vignetting’ phenomenon takes place if openings of other elements interfear
with the above.
Diffraction
Deviation of the direction of propagation of radiation, determined by its wave nature,
which occurs when the waves are restricted by obstacles.
Diffuse lighting
Lighting in which the light on the work surface or on an object does not come from
any particular direction.
