U@ColSebastianMoran thank you forthe suggestions.
I’ve discovered that holding for a couple of seconds your finger locks focus in iphone default camera app.
This helps a little.
From the zeiss website:
The macro-zoom lens with a focal length of 40 to 80 millimeters is the first and only smartphone accessory lens with a variable focal length setting. In combination with the optics of the smartphone camera, turning the ring does not increase or reduce the field of view. The ring functions much like a manual focus with which different planes can be set into focus. Depending on the setting, objects that are three to five centimeters away or five to eight centimeters away can be captured, enabling the full-frame razor-sharp capture of objects approximately three to twelve centimeters in size using the macro-zoom lens.
The supplied detachable semi-transparent diffuser can be used as a spacer. This ensures that the object is illuminated evenly and enables convenient focusing, even with a short object distance and a shallow depth of field.
I have attached a screenshot of film lab positive because the app crash when I try to save the image to camera roll
My image has been taken on the amazon river in colombia two years ago. Thank you for the pleasing comparison