Tamron SP 17mm f/3.5 is an ultra-wide angle, high speed lens with an almost non-existent lateral color. Tamron 17mm is a stunning ultra wide angle lens with excellent sharpness and contrast across the film plane, except in the extreme corners at wider apertures. Its optical design employs Performance is slightly to moderately soft towards the corners wide open at F/3.5, improves at F/4, is very good by F/5.6, and is excellent between F/8 to F/16. It has a built-in filters for black and white photography. Distortion is effectively controlled (about 1%) except that the this distortion is non-linear and varies from a very slight pincushion to a very slight barrel from about 40% off-axis to about 70% off-axis. Yet distortion along all four edges of the film plane is almost non-existent.