Very interesting results when comparing the FE 20/1.8 G to the FE 24/1.4 GM. For the price difference, I was expecting the GM to perform better at infinity distance but it's not the case, especially at wider apertures. From testing the FE 24/1.4 GM's corners + mid-field against other lenses, I knew that astigmatism was an issue but starting at f/2.8, this wasn't an issue for the FE 20/1.8 G,. At f/4 and smaller apertures, it performed noticeably better than the GM across the entire image field. As a matter of fact, at f/4 and smaller apertures, there 20/1.8's performs at Loxia 21/2.8 level in regards to resolution and contrast but without any field curvature and with better CA correction. The Sigma 14-24/2.8 competed neck and neck with the Sony 20/1.8 G with perhaps only slight better corners at f/5.6 but it could not keep up with the amazing FE 20/1.8 center resolution at larger apertures. I highly recommend the FE 20/1.8 G prime!
