Optical illusions fascinate me. The shadows from the morning sun make the grout lines between these bricks appear to bulge up. I know that they are concave but the more I stare at this photo, the bulgier the lines appear.
Focal Length 300mm
ISO 100
f/5.6
1/400
WB Fine Weather
SOOC
Amazing! I would swear they are puffed up and not concave. Very cool!