I always thougth the 1.7 was the best one of all of them. I have the 1.4 and 1.7 versions. The 1.7's are cheap, fast 'nuf. I don't think an extra .3 stops is worth it getting the 1.4. The 1.7 version I have is 49mm thread and the 1.4 is 55mm filters. I forgot the site but dang, it was comparing all the 50mm from Canon, Nikon, Konica and Minolta, need to find the bookmark on another computer but the lowly 50mm 1.7 was just under the performance of the Leica 50mm. But that's if you like to shoot pictures of walls and newspapers You know what I'm talking 'bout...those guys who buy lenses and just do performance testing out of it by shooting USAF resolution charts.