Im honestly about to lose my mind with this Sigma 35mm. I shoot mainly street stuff around downtown Chicago and lately the corner softness is just driving me nuts. Ive spent way too much money already trying to get that crisp, professional look but nothing seems to cut it for my SL2. I really need something that is sharp edge-to-edge because my clients are starting to notice the blurriness in the prints. My budget is around 2k and I need to make a move by next month before my next big gig. Is there actually a prime lens for the L-mount that is genuinely sharp or am I just chasing a ghost here?
Honestly, if you want corner-to-corner perfection, you really need to look at the Leica APO-Summicron-SL 35mm f/2 ASPH. It is pricey, but man, the glass is just unreal. Be careful with those third-party lenses because the L-mount performance varies a ton. You might want to consider renting it first since it's a big investment, but it's basically the gold standard for your SL2.
Building on the earlier suggestion, I totally feel your pain. I had issues with that same lens and honestly, it just isnt as good as expected for high-end work. Youre not chasing a ghost, but you might be let down by third-party optics if youre printing large. I ended up switching to the Leica Summilux-SL 50mm f/1.4 ASPH and the difference is night and day. It handles diffraction so much better than the standard stuff. Basically, the others mentioned the APO version and bad filters, which is 100% true. If you need corner sharpness that holds up for clients, stop wasting cash on gear that hits a wall. Just save up for the native glass. It hurts the wallet, but for professional prints, theres no substitute. Don't settle for less.
^ This. Also, watch out for filter quality! I once ruined a shoot thinking my lens was soft, but it was just a cheap filter killing my contrast. Total nightmare.