SEL 35F18 review @ Kurt Munger

I'm not saying the lens is sharper in RAW...the lens is irrelevant. RAWs will always retain more detail than JPEGs, as every camera out there applies some compression when producing a JPEG. Therefore if you want to truly scope out the sharpness of a lens, RAW is the only way to do it.

How many f/1.8 lenses have you ever used that were pin sharp wide open? Any time you buy a fast lens you should be working under the assumption that it's not going to get optimally sharp until it's stopped down a bit. You may consider any f-stop faster than 2.2 to be unusable (though judging by samples I'd disagree...obviously you're not going to be printing 30x45 posters, but who would expect that from that kind of setting?), but at least you have the option, where you wouldn't with the Sigma.