What were you expecting? Did you review the lens specs prior to purchase?
http://www.zeissimages.com/mtf/cf/Distagon4_50mm_CF_104908_e.pdf
BTW I use the Rolleiflex 50mm Distgon PQ for 60% of all my rollfilm work. It is a great lens.
An interesting thing about the lens is the light falloff curves for the 38mm Biogon, 40mm Distagon and the 50mm Distagon are all about the same wide open. When stopped down, the 50mm is the best. The Hasselblad version should serve you well.