I have used this on DX and FX cameras. On the DX (Nikon D300) the image is very sharp and the images have very good contrast. With a full-frame FX sensor (I used the D800), the outer edges of the image aren't as sharp as the center. This is a common problem with zoom lenses in general, especially at wide zoom ranges, and the D800 is a camera with such high resolution that it can exaggerate the shortcomings of any lens. In fact, this lens is significantly sharper than some of my other prime (i.e. non-zoom) lenses. Ken Rockwell is right, this lens is undervalued and now that word has spread its value has increased.