For a long time, I was making closeup photographs of flat surfaces using my cropped DLSR and Canon EF 50/1.4 lens. The scene was illuminated by an external flash. The focusing distance was the closest as the lens could give (0.45m). The sharpness of the image at the center and the corners was suitable to me.
Recently I have switched to a full frame camera and noticed that all the photographs are very soft at the corners (however sharp at the center). For the first time I understood that this lens (50/1.4) may be not the best lens for the kind of the photos I'm taking. Some people say that macro lens is more suitable for my situation.
Here's the 100% crops from the photo I've made using Canon EF 50/1.4 on a full frame sensor at the closest focusing distance (approx. 0.45m), f/11, ISO 100, manual focusing using liveview, camera standing on a tripod, direct external speedlight type flash to the right of subject:
So, here's the question: what lenses could solve the problem of soft sharpness at the corners in my situation?