I have an iPhone 16 Pro Max and it takes generally great pictures. While troubleshooting some focus issues, I discovered the EXIF Metadata fields ‘FocusDistanceRange’, ‘AFPerformance’, ‘FocusPosition’, ‘AFMeasuredDepth’, and ‘AFConfidence’. These are all visible in the ‘Maker Notes’ section, and I’m using Phil Harvey’s EXIFTool (with EXIFGui) to view the data (not all EXIF metadata viewers present the full set of EXIF data).
Note that not all these fields are present in every photo; they are generally present on a typical landscape photo taken with the main ’24mm’ (6.8mm) lens (at least).
Focusing primarily on ‘FocusDistanceRange’ and ‘AFMeasuredDepth’, I’m trying to determine what the camera thought was the focus distance for a given shot. The numbers in these fields are not making sense on my pictures.
Perplexity AI describes ‘FocusDistanceRange’ as follows "In maker notes, FocusDistanceRange generally refers to a pair of values giving the lower and upper bounds of the camera’s estimated in-focus subject distance at the time of exposure" (Perplexity gives references but I can’t find that definition in those references; nonetheless, it makes perfect sense as an explanation). ‘AFMeasuredDepth’ is described as "AFMeasuredDepth is a maker note tag that records the camera’s estimate of subject distance as measured by the autofocus system at the time of exposure, typically expressed in some distance unit".
I have scrolled through dozens of distant landscape photos (no close-by objects), using EXIFGui, and cannot find a single photo that has a FocusDistanceRange upper limit greater than 4 meters; most don’t go above 2 meters. Two pictures, taken seconds apart of distant mountain peaks (and both in focus), have ranges 0.38-0.99m, and 0.61-1.64m. In both cases, I would have expected the upper range to be ‘infinity’ or a large number. For these two pictures, ‘AFMeasuredDepth’ is 1077 and 1078 respectively (no units stated).
Does anyone know how to make sense of these figures?
EDIT TO ADD: While the Maker Notes entries are not officially published/supported by Apple, there is considerable commonality among different manufacturers in their use of Maker Notes, so they aren’t just unique creations by Apple. Here’s a composite image showing the four images I’m troubleshooting, with some key maker notes pasted in the corners. The ‘Focus Region’ is drawn by me, based on what is revealed in ExifGUI.
