Candela was chosen so that the new definition would precisely match the old definition. Although the candela is now defined in terms of the second (an SI base unit) and the watt (a derived SI unit), the candela remains a base unit of the SI system, by definition. If a source emits a known luminous intensity "I" (in candelas) in a well-defined cone, the total luminous flux "Φ" in lumens is given by where "A" is the "radiation angle" of the lamp—the full vertex angle of the emission cone. For example, a lamp that emits 590 cd with a radiation angle
Félix Candela Félix Candela Félix Candela Outeriño (; January 27, 1910 – December 7, 1997) was a Spanish and Mexican architect who was born in Madrid and at the age of 26, emigrated to Mexico, acquiring double nationality. He is known for his significant role in the development of Mexican architecture and structural engineering. Candela’s major contribution to architecture was the development of thin shells made out of reinforced concrete, popularly known as "cascarones". He was a teacher of Santiago Calatrava, which has had a great influence on Calatrava's works. Felix Candela was born in Madrid, Spain in 1910. In 1927 Candela