No not really correct
- If you call the “wide” lens the basic lens then that is 1X (not 0)
- The Ultra Wide lens is 0.5X relative to the Wide lens (or as Apple say “2x optical zoom out”)
- The Telephoto lens is 2.5X relative to the Wide lens, or 5X relative to the Ultra Wide lens (hence the 5X claim, apple say “2.5X optical zoom in / 5x zoom range”)
But... none of the lenses on the iPhone are optical zoom lenses, as someone above said they are all “prime” lenses i.e. fixed at different “zoom levels” i.e. focal lengths (0.5x, 1x, 2.5x zoom levels above). The iPhone computers do the “zooming” in between based on manipulating data from the three fixed lenses., so try and pretend you are using a traditional zoom lens through the whole range. So yes you do lose detail at various points in the range due to digital cropping as you move through the “zoom range” unless you happen to be at 0.5x 1x or 2.5x exactly etc.
The pictures attached show the difference from my iPhone 11 Pro just now, the same fragment of picture taken from the Ultrawide lens (zoom level at 0.9x, unclear) and then the Wide lens (zoom level 1.0x, clear). Why so different? Apart from other sensor/lens differences, at 0.9x the Ultrawide lens has had to digitally zoom in/crop...