The QBM 135/2.8 Sonnar had a slightly different optical layout compared to the C/Y Sonnar.
Rolleiflex QBM Contax C/Y
<p">This is one of my favourite lens and I like taking photos in the 135mm focal range. At f2.8 you still have a chance to take pictures at 1/60. The Sonnar signature is nice and sweet. This is the lens that lure me into Zeiss optics. Probably not the sharpest 135mm you can get. But Zeiss telephotos have never been the sharpest, but certainly smooth and not harsh.
Rolleiflex SL 2000 F f4 1/125 135/2.8 HFT Sonnar Ektar 25
Rolleiflex 3003 f2.8 1/125 135/2.8 HFT Sonnar Ektar 100