Luminous intensity base dimension

Today, based on what we know about our physical world, we need seven juudamental or base dimensions to correctly express what we know of the natural world. They are length, mass, lime, temperature, electric current, amount of substance, and luminous intensity. With the help of these base dimensions we can derive all other necessary physical quantities that describe how nature works. 

In addition to these two radiometric assessments of the beam intensity, for beams of visible light there is a third possibility, which is to quantify the intensity of the beam by the intensity of visual perception by the human eye. Physical quantities connected with this physiological type of assessment are called photometric quantities, in contrast to the two radiometric quantities described above. In photometry, the intensity of the beam is called the luminous intensity 7y. The subscript v stands for visual . The luminous intensity 7v is an ISO recommended base quantity the corresponding SI base unit is the candela (cd). The luminous flux is determined as the product of the luminous intensity and the solid angle. Its dimensions therefore are luminous intensity times solid angle, so that the SI unit of the luminous flux < v turns out to be candela times steradian (cd sr). A derived unit, the lumen (Im), such that 1 Im = 1 cd sr, has been introduced for this product. 

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