I have 7 Praktica B camera's and about 14 lenses including a Carl Zeiss Jena 50mm F1.4, also the pentacon F1.8 and zeiss Tessar F2.8.
I have the Pentacon f1.8 50mm and the Tessar in 42mm format as well, also have the adapter for these, the results are very good, they are both sharp lenses.
I have just bid on one of the PB to EOS adapters because I want to use the 50 F1.4 Zeiss on my 350d.
I have used Praktica cameras since 1972 and have never had any complaints about picture quality from any of their lenses or those made by Sigma.
The Pentacon club magazine which ran for 16 years contains many hundreds of pin sharp photo's taken with Praktica and Sigma lenses.
John