- Posts: 4
- Joined: Fri Feb 07, 2020 5:11 am
- Real Name: Karl Meyer
No, what BMD state’s is, the Sigma f/1.8 setting on the lens is actually closer to f/1.7 as measured, so the camera sets the actual f/stop. Sigma listed the lens as f/1.8, because the math is probably between the two, but closer to f/1.7, so Sigma lists it as f/1.8, to error on the side of caution. This is interesting in that most of the time, manufacturers will opt for the better specification.
Focal length specifications are also similarly listed, and are rounded up/down from actual lens focal length. Very few 35mm to 50mm lenses, for example are actually 35mm or 50mm, but can vary from one to three millimeters. The actual focal length and iris pupil opening measurement is used to determine the f/stop.
Cheers