The difference between the f/1.8 and f/1.4 versions of this lens lies in the build quality. Both are of high optical quality and both work in the same way. If you're hard on your gear, if you're a pro using your gear on a daily basis, the f/1.4 version might come in handy as it's designed for heavy use and some abuse. If, like me, you take care of your gear and don't depend on earning your living, you can save a lot of money by buying a 35/1.8 lens.
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