High Definition TV is all digital. So if you have HD footage from a TV series, actually made in HD in the first place, you should be able to see it perfectly on your TV exactly as the producer wanted it to be seen.
There really is no reason to change it. Indeed, changing it in any way is more work for the TV channel, etc. It is bad enough they slap their damn logo on the image, but why make any changes?
I am sure I have blogged, like many others, on the total stupidity of overscan on HD TVs. TV screens are made with 1920x1080 pixels for full HD to match the format, and a full HD source should put the 1920x1080 pixels from the source on to the TV one-to-one. But for some stupid, and largely historical, reason some TVs are set, by default, to scale up the image so that we see slightly less than the full width and height stretched to TV size. This makes every single pixel softer as it is a calculated value from adjacent pixels. They are quite good at it, but it is different to the original and not as clear. Make sure you always set your HD TV to show HD images correctly and turn off overscan.
But I have started to notice some serious problems with some HD channels. Notable watching NCIS on Universal HD (on Sky), the colour is adjusted. Only during the programme, not the adverts, but people have red faces. It looks shite. Watching NCIS on another channel like FOX HD is fine.
Why the hell would anyone adjust an HD programme? Why not send each pixel as is without scaling or adjusting or anything. That gives the producer the best chance of showing the viewer what they intended. Yes, TVs have adjustments, though that really is a tad unnecessary though local lighting and colours could be relevant then.