I asked because i suspected a wide angle, this effect is very typical of wide angled lenses just look at the effect you get at 10mm its much more pronounced but it gives you converging verticals and things look bent and much larger towards the middle of the image. As someone has said already don't go below 50mm for portraits as that is what is equal to how the human eye sees things anything below is distorted to fit in, and thats not flattering for anyone unless used in a creative manner.