Man @ Work -- NEX-5N & Carl Zeiss Distagon 35mm f2.8 QBM @ f8. Click for larger.
Finally got a chance to take out the Rollei QBM [Quick Bayonet Mount] lens for a spin. It's been a while since I bought this lens at the photo show. I was wondering if this older lens would perform similarly as the Yashica/Contax version of the Distagon 35mm f2.8. Although I was kind of expecting the contrast may not be as good as the Y/C version, as this one does not have the HFT coating, where as the Y/C version has the famous T* coating. I got what I expected. While it's a nice lens, the contrast and sharpness of the Carl Zeiss 35mm f2.8 Distagon QBM is behind the Y/C counterpart. Of course, this could be a copy variant, since I don't have another copy to test. I think this lens has de-centering issue as the left side is slightly more blurry at the edges than the right edge. It could also be the cheap QBM to NEX adapter too.
In terms of build quality, both the Y/C and the original Carl Zeiss Distagon are excellent. The Y/C version is slightly larger with a 55mm filter size whereas the other has a 49mm. Looking at both lenses, the Y/C version has almost no reflection while the other shows far more reflection. Both focus very smoothly and a joy to use.
I think I prefer the Yashica/Contax version of the Distagon over the non-HFT QBM from the image quality perspective. They are both excellent lenses.