EXAMPLE 1:
AOV FOR 45mm LENS & full-frame 35mm
35mm full-frame FORMAT = 36 x 24mm
FORMAT DIAGONAL = d
d = √w2 + l2
d = √362 + 242
d = 43.3mm
FOCAL LENGTH = f
f = 45mm
AOV = 2 × Arctan((43.3÷2)÷45) = 51.4°
EXAMPLE 2:
AOV FOR 45mm LENS & half-frame 35mm
35mm half-frame FORMAT = 18x24mm
FORMAT DIAGONAL = d
d = √w2 + l2
d = √182 + 242
d = 30mm
FOCAL LENGTH = f
f = 45mm
AOV = 2 × Arctan((30 ÷ 2) ÷ 45) = 37°