I just got some test rolls back that I took with the Zeiss Ikon Nettar. At wide open the f6.3 Novar Anastigmat have some really pronounced vignetting, which gets better as soon as you stop down a bit. The sharpness is not excellent wide open but turns out sharp when stopped down past f11.
I was a bit surprised at the contrast and punch in the colours that this old lens delivers, and I guess it would have been even better if I had used a lens hood. The lens focuses great at close and medium distanses, but at infinity it overshoots, so in order to get pin sharp landscape shots I have to set focus a bit before infinity.
I also noticed that the shots were framed a bit higher than I had actually framed the shots so the viewfinder is not so precise for advanced framing and composition work.
The film I used was Kodak Portra 400.