I don't have any problems with my Helios right now. I spend 5 hours a week doing portraits in the room with white walls, which i usually cover with some backgrounds. I thought that this lenses would increase the sharpness and quality of the pictures, and that Praktica wouldn't be the best camera to use with these lenses. Thanks for advice - now i know that there's no difference in quality between these two cameras. I have another question: is the Takumar 1.8/50 comparable to Helios? And what other 50 mm lenses would you reccomend?