Originally posted by BarneyL Sony 20mm 1.8 has 67mm filter and weighs 373 grams. I feel that for the DFA 21, F2 should be achievable.
But the Sony 20/1.8 looks like it's about 2cm longer than the Pentax DFA21 and this is with a short flange distance design. The front element looks larger as well. These things considered the DFA21 will have to be slower or perform very "differently"
MTF's can lie, and it's the wrong fl, but the new Samyang 24 does look very good as well and a bit closer in size. Perhaps UWA's are indeed improving as much as is said. Here's hoping that it's not the famous short flange advantage starting to show up. The price of that performance, if true, is shockingly low.
Samyang Optics