Other factors to consider are ......how high is the light from bulb to floor..?? are you working on a bench or table..? how high is that table top work surface from floor ..? what is the distance from the bulb to the table top or work surface..?? what is the lumens spread from bulb to the work. surface ..?? every bulb has a diiferent light pattern and lumen strength ..
Lets say the bottom of the light fixtures is 10 ft above finished floor ...if you were working on the floor you would want the floor to be nice and bright evenly lit with no dark spots .... but we are not working on the nasty dirty floor are we...!!
all right now you are working on a bench of sorts ....say 3 ft to surface .....10 - 3 = 7 ft tween light and work surface now you need to figure your light pattern and corresponding lumen strength to provide enough even light to cover your working area without shadowing if more then one fixture over head .
there is a lot of complex calculations that go into lighting up a given area......Hell ...i been working in a 500,000 sq ft Amazon warehouse over the last month and a half ..the flourecent tube lights are easily 25 ft over my head....hanging down 10 ft from the roof beams..... i sure as Hell would not want to be the person in charge of figuring out the lighting requirements for that warehouse .. .makes my head hurt just thinking bout it..!!
this is how they light up retail stores and such by knowing what type of lighting is going to be used and the height it will be at then they figure out the type of bulb needed and the minumum lumen strength to give even light over a given circumfrence area and the number of lights need over total square footage of space.