I've tried this with many phone cameras and almost all of them focused well for macros but only for a moment before they defocus to focus something further behind. If the camera can focus on objects such close then why do they do defocus from that distance? Also I haven't compared this with an app with manual focus, the above mentioned issue is with auto-focus.

  • Which version of iPhone?
    – Pacerier
    Dec 22 '15 at 4:07

I have observed the same, I have also observed in the past that it's very hard to accurately judge focus on a live lcd without specific focus aid features like focus peaking or zoom.

My assumption therefore is that the camera's minimum focus distance is enough to make the subject look superficially in focus but not to qualify as a lock for the AF system. Having failed to lock on, it winds out to a longer distance and may achieve focus lock on the background.

If this is the case, then moving a little bit further from the subject should allow a lock to be achieved.

  • My question is why is the minimum focus distance different from AF lock distance Sep 22 '15 at 20:08
  • There's a minimum distance that the lens can focus, for the sake of argument let's say 5mm. What I suspect is happening is that the object is slightly closer to the camera than that, say 4.9mm. Sep 22 '15 at 20:45
  • The point being that it's very nearly but not quite possible to achieve correct focus. In this situation it might well look like the subject is in focus on the live lcd screen, even though the AF is unable to lock on. If the camera were to fire in that situation, the resulting image would be just ever so slightly out of focus. Sep 22 '15 at 20:48
  • But if I'm seeing the image get focused for a fraction of a second, even if it's for that fraction doesn't it mean that the camera in fact can focus at 4.9, so if it is capable why does it end up locking at 5 or anything more than 4.9? Sep 22 '15 at 20:49
  • Does the camera indicate correct focus? Or does it just look focused? I've been assuming the latter. Sep 22 '15 at 20:50

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