Digital Cinematography, 2nd Edition

146 Chapter 7

Table 7.1 (Continued)

Aperture Mathematical f Number Mathematical

Value Formula (N) Value

11 √(2

11

) 45 45.25…

12 √(2

12

) 64 64

13 √(2

13

) 90 90.51…

14 √(2

14

) 128 128

15 √(2

15

) 180 181.02…

16 √(2

16

) 256 256

lens can deliver to the sensor. The scene being

photographed modulates in frequency and con-

trast. The lens attempts to accurately transfer that

information to the sensor, the ratio of the result-

ing reduction in contrast to the original scene

contrast is a mathematical function expressed as a

percentage; that percentage is the metric of MTF.

Figure 7.7 Cinema lenses are calibrated in T-stops.

Cinema lenses are rated in T-stops ...