Man, what a tough competition. The 40 is built better, but 2.8 compared to 1.8, and even if the nifty gets a tad sharper at F2, it's still faster than the 40. The 40 cost a tad more, but go in to the Nift Fifty sample thread and those pics look just as amazing to me as the pics in the 40 sample thread. The 40 has better bokey supposedly, but I'm just sayin, go to the fifty sample thread and there are some absolutely great pics, and this lens is faster while the 40 has the better build. So which one to get for my 5D2. I already have the tamron 28-75 and it covers 40mm at 2.8, so the nifty is the one that would give me something that I do not have, namely 50mm at 21.8, 2.0, 2.3. Just wondering what everyone's thoughts are.