aw  = maximum aperture widht

ah  = aperture height


Relative Width of the Aperture
RAW = aw/ah



 

Very Narrow
RAW < 0.10

voluminalis [0.08]

Narrow
0.10 ≤ RAW ≤ 0.13

pretiosus [0.11]

Medium
0.14 ≤ RAW ≤ 0.17

spectrum [0.16]
Broad
0.18 ≤ RAW ≤ 0.21

bullatus [0.19]

 Very Broad
RAW > 0.21

geographus [0.23]