I understand I am comparing Fuji Apples to Gala Apples, but when I compare the image quality from this cheap, plastic-bodied prime lens to those from my several L-series Canon zooms, there is no contest: this lens outperforms. Now to those who say one cannot compare a prime to a zoom, I say: why not? Aren't we discussing image quality or are we discussing something else?Given the very large images produced by modern DSLRs, I can crop the image from this 50mm and get the zoom effect I need given the minimum zoom of 50mm (times crop factor). I can also place this lens on my Elan 7 film camera and get spectacular results. I use this lens more and more and zoom using my physical zoom (feet) and digital zoom (Photoshop or Aperture or any image editing software). The results are always great. No, I cannot print to 40x60 inches if I crop from this lens, but I am not planning to do that anyway.When I shoot a wedding (not bridal portraits, I use the 85mm prime for that) the photos made using this lens are always the best and always the favorites. I know it does not have the little red ring around it but that is just to show other photographers that you are hip and with it, not necessarily to get better images and certainly not based on the money-to-image-quality ratio. Nope, buying a more expensive camera or a more expensive lens will NOT make you a better photographer. Using a prime lens, however, like this very affordable option, will certainly improve your images.The cons are obvious: low build quality. This means that the lens is likely to last for only ten years or so, judging by the fact that other Canon primes (and all Canon lenses in general) are notoriously and incredibly reliable (the more expensive f/1.4 version of this lens a notable exception, but still very, very, very reliable).The sum of all my comments is but this: for the money, there is no finer nor more useful lens for your Canon EOS Camera. 

Question: What is the difference of iii to v?
Answer: image quality from this