Mystery focus?

Nesster · Expire: 2014-02-20

This photo has something interesting - the out of focus pavement goes into focus in both lower corners! Fuji ST605, Yashinon DX 35/2.8, Ilford XP2. I had the lens stopped down a couple of stops, as it was a bright morning and the Fuji's top speed is 700...

LucisPictor · Expire: 2013-12-03

Probably "Bildfeldwölbung".

I don't know the English term for it.

Nesster · Expire: 2014-02-20

Ah, thank you Lucis... field curvature in english I think.

The focus at the edges is further (?! I expected closer!)

Seems like the field curve makes the edges focus further than the center. Therefore the pavement out of focus in the center comes into focus in the far corners.

Also, this phenomenon will only show on film, with APS the zone's out of frame.