I would like to know what the equivalent focal lengths are when in digital zoom on an iPhone 13 Max Pro – greater than 3X to 15X.
The equivalent focal lengths of the three cameras in the iPhone 13 Pro Max are:
- [ultrawide] 13mm [1/3.4" sensor, 8.18x crop, so really a 1.5mm lens]
- [primary] 26mm [1/1.65" sensor, 4.46x crop, so really a 5.8mm lens]
- [tele] 77mm [1/3.4" sensor, 8.18x crop, so really a 9.4mm lens]
The optical zoom factors are all calculated relative to the primary camera:
- 13mm/26 = 0.5x
- 26mm/26 = 1x
- 77m/26 ≅ 3x
so just take the zoom factor, multiply it by 26mm and you'll get the equivalent FoV focal length. E.g., 15x26mm = 390mm.
But, of course, digital zooming is really just cropping and upscaling, so it's not really equivalent to using a different focal length. See also: What is crop factor and how does it relate to focal length?