Hi all,
My Componon-S 180/5.6 (the one with the blue rim) show what I consider an excessive amount of field curvature at small magnifications. I need to stop it down beyond f11 to get a barely acceptable flat field (to my taste). The lens is very sharp and perfectly centered, so I think it is its normal behavior.

I wonder if it is normal with other lenses in this range. Maybe the working aperture of this lens is f16-22... I bet neither of my other lenses are that bizarre (Apo-Rodagons, from 50 to 150mm).

Could you advice me a proven, better lens? I`d prefer to stay in 180mm; a 210mm lens imply the need of building a new cone, something I`d like to avoid -unless there is no other option- (It is really hard to find parts for my 5x7" enlarger).
Thanks.