I worked really hard on this photo,to adequately sharpen the original over-5-megabyte file adequately without unduly emphasizing the jaggies on the multitude of strong,high-contrast window and balcony edges.Look at the window and balcony openings,and you can see the stairstepping effect. At 100% pixels, one can see the lens has some lateral chromatic aberration visible on each and every window and balcony on the upper right hand side of the original capture, but at this web-reduced size, the CA is hard to see. The CA really isn't nearly as troubling to me as are stairstepping effects on strong,high-contrast edges. The original,full sized image is at http://img.product.pchome.net/sample_pic/00/04/61/92/46192_1_10. In that original JPG you can see the stairstepping problem around each of the window and balcony openings where the light-colored masonry stands out against the shadowed areas. Shutter speed is high,aperture is f/6.3, but this lens at 18mm looks like crap.