Hi!
After some extensive search on the Net, I wasn't able to find any useful information on this matter. Any help or tip would be greatly appreciated!
For the purpose of doing various angular measurements on our C++ image analysis software coupled with a SQL camera database, we do not have any problems with most of the smartphones brands (Samsung, Huawei...) when it comes to digital zoom, but really don't understand how Apple manage it...
As usual, in the absence of digital zoom, field of view (FOV) may be directly derived from 35 mm equivalent focal length.
However, in case of digital zoom for an iPhone device, how can we derive the FOV from 35 mm equivalent focal length and digital zoom ratio?
And what about the mixed optical/digital zoom since the iPhone 7?
Thanks! :)
I don't know if this helps or not but, with a test image from my iPhone 12, I get...
[Composite] Focal Length : 4.2 mm (35 mm equivalent: 108.0 mm)
... as well as...
[EXIF] Digital Zoom Ratio : 4.2
[EXIF] Focal Length : 4.2 mm
[EXIF] Focal Length In 35mm Format : 108 mm
Thank you Joanna for this test!
We do know the DZR exif data and already used it in our own tests.
What we don't know is how, for some brands and cameras (and especially Apple), to properly derive the angular FOV with this DZR and the 35 mm FL, as (to be more precise) it seems that it also works differently depending of the camera used.
We're also aware of the "mixed" optical/digital zoom since the iPhone 7.
As an example, I've attached a part of our (big!) Excel spreadsheet with some photo tests using the full moon as a reference for measuring an angular size (which is 0,5°).
As you can see, it works fine with the iPhone 5s, but not with the iPhone 6 and 7.