Here is chart converting Klett units (using a green filter) determined experimentally for S. aureus by Avi Rasooly: Klett O.D. at 550 nm 240 2.0 220 1.85 195 1.75 182 1.65 155 1.48 133 1.30 112 1.10 85 0.89 55 0.60 30 0.34 16 0.165