I am currently shooting with a Schneider Symmar 150mm f5.6 convertible lense and I am considering purchasing a Rodenstock Sironar-S 135mm. I shoot black & white landscapes and would like to get opinions on the type of image quality difference between these two lenses. The first question is, all things considered equal, will their be a quite noticeable difference in image sharpness / contrast / quality between the two lenses? I shoot most of my shots in low light at the end of the day with my camera very seldom aimed at the sun. The second question is, would the change in lense be worth the expense for the quality improvement?