Version II is about 0.2 brighter than version I. Generally speaking, version II has slightly better border and corner sharpness than the previous version but nothing to write home about. Version II seems to be slightly worse than version I at 24mm. They are about the same at intermediate FLs (50mm to 70mm). Value For Money. Currently, this lens is available for around £405, which seems quite reasonable. Canon's 24-105mm f/4L IS USM is the closest equivalent, costing £640, which has a constant f/4 Q0FvS.