>>2995071I know.
Anyway, I just measured the size of the front element (from product pictures), 16.4mm.
Using 58.8 degrees angle of view(diagonal), dividing that by two, moving 1cm "above" the front element, forming a right angled triangle, the lens will actually see the edges of a filter thats 51.8mm in diameter.
17.7mm*2+16.4mm = 51.8mm
Guess the 52mm filter thread is spot on.
Pic related