Originally posted by Medex I could confirm that dfa* 50 has some coma issue mostly in the corners wide open that practically dissapears at f2.8-3.2.
When using the naming conventions used
here I'd say that the lens shows no comatic aberrations, no tangential astigmatism and mild sagittal astigmatism.
The Sigma 50mm F1.4 Art shows about the same mild sagittal astigmatism plus some mild external comatic aberrrations.
I am quite sure that none of those two portrait lenses have been designed with any focus on astrophotography and quite rightfully so.