I got my SUN last month and have been shooting some tests. I feel it's so much easier to focus and sharper than my Sankor 16C. Interesting enough that I also disassembled it because of the red line, which I think is for the center alignment reference, isn't centered. But I didn't find a way to fix that. Actually I don't need the line because I usually use a flashlight pointing to the lens to make sure horizontal flare is even.