Reported to a lesser extent in the predecessor S22, the flaw appears to be in the shape of the Galaxy S23 lens, with Samsung trying unsuccessfully to mask it using image processing algorithms.
Demonstrated with photos taken using the phones of several S23 users, the flaw manifests itself as optical aberrations apparently induced by the shape of the lenses, which are too small to evenly focus the image on the relatively large optical sensor.
The problems appear to manifest themselves in both the Galaxy S23 series and the S23 Plus, with the substantially different photo configuration appearing to exempt the S23 Ultra from these problems.
According to discussions appearing for the German Notebookcheck forum, the defect can manifest itself in a circled area of the image, but only predominantly in certain regions. The problem seems to be magnified in close-up pictures, which show a lot of detailed content, like blades of grass on a lawn. Judging by the radial arrangement of the focus defects, it is unlikely that the problem is software, or that the image processing algorithms can compensate for the missing detail.
At the moment, the focus defect that could be replicated even on phones sent to publications for review has no explanation from Samsung. The only encouraging aspect would be that there are indications that the problems would be restricted only to certain batches of S23 phones and, in any case, not manifest in all the pictures taken.