My guess is that they designed a standard 50mm f:1.4 and then sent it to Carsten for evaluation. As could be expected, he made a comment about a few extreme corner pixels being just the slightest bit unsharp, so Zeiss decided to call it a 55mm so as to have perfect corner sharpness and contrast even wide open. :
Hehe, I wish! This lens is very interesting to me, but I am afraid of losing some of the 50P's character, so I am very cautious about wanting it. Ultimately if it is what I want, I would probably sell three lenses (Sigma 50/1.4, 50P, 50MP), but that is a very big IF.
