I have one of the lower priced DOF adapters. I shot someone wearing a white suit and his right arm has a very prominent chromatic aberration. I shot another person also wearing a white suite and he also had that chromatic aberration. My lens is a Nikon 50mm f1.4 lens at wide open. I placed a 1 inch++ extension tube between the achromat and the condenser so as to magnify the image and get rid of the vignette. Do you think the extension tube is what's causing the CA? Thanks guys!