The Canon EF 40mm f2.8 is fun lens for DSLRs but with adapter to mirrorless bodies, the adapter eats the small size benefit as with the other small SLR-era lenses.
Sony has been keeping the mirrorless full-frame lenses quite small. The old Sony 55mm f1.8 (which I count to be in the class of 50 mms) is still sensibly sized (less than 300 grams) although a bit prone to flares but otherwise quite close to Otus class sharpness.
And then there's the Sony's 50mm F1.2 GM halo product which is still less than 800 grams. It seems that they are pushing down the weight at the same time they are improving the image quality.
Sigma's lenses are a lot of cheaper than Sony's GM lenses but they are bigger and heavier in many cases and in some cases they are still are old designs for DSLRs.
Sony has been keeping the mirrorless full-frame lenses quite small. The old Sony 55mm f1.8 (which I count to be in the class of 50 mms) is still sensibly sized (less than 300 grams) although a bit prone to flares but otherwise quite close to Otus class sharpness.
And then there's the Sony's 50mm F1.2 GM halo product which is still less than 800 grams. It seems that they are pushing down the weight at the same time they are improving the image quality.
Sigma's lenses are a lot of cheaper than Sony's GM lenses but they are bigger and heavier in many cases and in some cases they are still are old designs for DSLRs.