Many thanks for the welcome and fast reply!
Well, I've inherit one of this* (have you seen it?) but I've found quite difficult to get some info about this particular model (here, at google...). For my needs (doing B&W solo) I think it's ok to focus and compose (well, I haven't try any lens with less than f/4.5).
Now I'm a bit more concerned about the sharpness and the quality of the glass between the f/5.4 and the f/4.
Is it worth to sell this one and upgrade to the f/4 (e.g. used on eBay)?
Ahh and sorry for my not so good english
*Arrg... I can't post links since I just have one post but you can find it on google images by searching "rodenstock rodagon 80mm f5.6 enlarging lens". Its the first with a red stripe