Olympus a200 teleconverter (1.5X)
Recently tested 60$ Olympus A200 teleconverter (1.5X) on Sony 50mm OSS and Sigma 60mm
Sigma 60mm creates more compression (as expected), Sony @f1.8 create more diffuse out of focus (as expected). Olympus does not affect resolution much but, I think, change a bit field curvature (center focus is slightly in front of corners), bad for painting reproduction but ok for portraits. Olympus may amplify already existing curvature in the lens.
As we already know Sigma is sharper than Sony (Sony 50mm catch up stopped down to 2.8 with Sigma@2.8 in center but corners are always sharper on Sigma).