Rear projection DLP TVs should ideally be placed at eye level. A four foot high shelf is too high for placement. If you place the sofa further back you will reduce the vertical viewing angle, which should help a little bit.
Best solution is to lower the TV. Then, when you are standing, the picture will look dim, but will look bright when you are sitting.
The vertical viewing angle does not seem to make an appreciable difference with direct view LCD and Plasma sets, but rear projection DLPs are really sensitive and work best at eye level.
In addition, if you lower the TV you will have less neck strain, though in a recliner it probably wouldn't matter if you were looking up.
As for tilting the TV, check with Samsung. 1-800- SAMSUNG.
Just got a 50" samsung rear projection tv. Placed it on my home build in entertaiment shelf. The shelve is about 4ft tall....so from floor to middle of tv is about 6'1 or 6'3. I currently have my sofa at about 7 or 8ft from the tv.
When I'm watching tv last night I notice its not as clear or as bright vs when i'm standing up. Whats the best solutions to my problem(No I am not buying another tv). I can maybe max move my sofa back another 2 ft that's it. should I tilt the tv forward?
need help. thx.

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