US primetime drama and comedy are traditionally shot on 35mm film, so there is no NTSC to PAL standards conversion. What you see on your screen is a PAL video transfer of the 35mm film prints, much like a PAL movie transfer. If the picture looks soft it's because of the lower frame-rate of film (usually 24 frames per second, shown at 25 to fit our TV system) compared with the 50 interlaced fields used in PAL video. Also, Americans like everyone to look golden, and over colour-correction can make things look soft.

Ironically, as 35mm film is inherently a high-definition format, old shows like the original Star Trek series (as well as TNG etc) can be shown in high-def, while tonight's Eastenders, and pretty much every other UK produced programme can't because they're shot on standard definition video (standard-def programmes can be upconverted to HD format, but I wouldn't call it proper HD).