Konica Minolta AF 50mm f/1.4
This lens behaves very well on a Sony full-frame sensor. The center resolution is very sharp and is easily found when stopping down to f/2.8. But you have to stop down to f/8 to find truly sharp edges. Vignetting is pronounced when fully opened, but almost vanishes at f/2.8, and completely disappears at f/5.6. Very good on a full-frame, this lens also provides very good definition on APS-C sensors.
The Konica Minolta AF 50 mm f/1.4 is good performer on any Sony sensor, suffering only from some soft edges at wide apertures.
Sony 50mm F/2.8 Macro
This Sony lens is one of the very few macro lenses listed here. In addition to its shorter focusing distance, its two main advantages are very good central resolution and almost no distortion. This is true for both APS-C and full-frame sensors. On a full-frame body, the center is very sharp even when wide open, but the edges are very soft. Stopping down to f/8 produces very good homogeneity. Slower than the Konica Minolta, this 50mm is also less sharp on an APS-C sensor.
The Sony 50mm f/2.8 Macro has perfect geometry and good definition on full-frame sensors, but is a bit soft on APS-C sensors.
Sony DT 50mm F1.8 SAM
Mounted on APS-C bodies, this 50mm proves very efficient, with a DxOMark score measured at 14 and reached at f/2.8. While similar in performance to the Konica Minolta lens listed above, this 50mm is even a bit sharper on an APS-C sensor. Moreover, it handles chromatic aberrations and distortion very well. The price-performance ratio is good. Sadly, however, you’ll have to choose a different lens if you use a full-frame body.
If you don’t intend to use a full-frame Sony body, the Sony DT 50mm F1.8 SAM 50mm is a good investment.
Pentax SMC D FA 50mm F/2.8 Macro
This Pentax macro lens is a solid competitor and behaves quite well on an APS-C sensor. It shows very good edges and a sharp center. But while the image field has good homogeneity whenfully opened, you have to stop down between f/5.6 and f/8 to reach the best resolution range. The remaining metrics are solid: no distortion, little vignetting, and very few chromatic aberrations contribute to a globally good lens.
The Pentax SMC D FA 50mm F3.8 Macro is a reliable lens, and is sharp when stopped down to f/5.6.