anyone got experience of this lens at f4 - one stop down - does it still deliver quality so wide?

my 80mm is poor till its 2 stops down, so I wonder if the 140 is the same.

wanted to check before I invest in one,

thanks.

I shoot portraits with this lens all the time at around f4-5.6 and have no complaints at all. Granted, I'm not hyper-critical, and I'm talking about portraits as opposed to landscapes, macro, or other work where there's a lot of micro detail.

I do not use stops at wide open or close to it often but I must say for those time I needed those f stops, they were quite good. The sharpness to the medium format level is very critical and subject to the lighting so I am not too sure if that was the reason but the 80mm is among the very best I have use as well as the 140mm, with Contax 645+P45. The 80mm when wide open is indeed very good at the center but of course it has some trade off at corners for its speed but I am found it a very useful lens.

narikin,
I'm on location for several days and away from my HD's for examples. I shoot the 140mm Contax all the time at F2.8 & F4 with wonderful results, I love this lens. As for the 80mm Contax lens, it is my absolute goto lens everyday, I'm attaching a shot with the P30 at 200iso 1/125th F2.8. I think that the 80mm Contax lens is extremely sharp near wide open, but is very hard to focus perfectly.
Hope this helps.

Cheers,