Lighting design is ultimately ...
Lighting design is ultimately not about numbers and calculations. It is about feelings and spontaneous reactions. Although the designer can calculate how 'big and bright' a fixture will be at any distance, from the manufacturer's data sheet, eventually he must just instinctively 'know', how a specific fixture will perform at any distance. This comes from both practice and experience.
Lighting Mechanics, by Bill Williams
Bill
Williams
Lighting