Thank you for your comments...had not really noticed that. Maybe it has comething to do with the surface of the building....topleft it's darkbrown wood, and bottom right it's light gray painted concret?
ps: this is the first picture ever that I have sold. The marketing boss for the company wanted the picture
pps: it's a hdr from 3 pictures, handheld and taken in aperture mode, 3 pictures 2 ev apart.
Equipment: Canon 20D, Sigma 15-30mm EX, Tamron 17-50mm 2.8 VC. Flickr page: www.flickr.com/jakupfr