On any LCD panel, some screen uniformity imperfections may exist, and these are manifested in what you described. While it shouldn't be annoying in regular viewing, what you can see is usually adjustable. If the problem persists, then it would have to be inspected and if possible, repaired.
Unfortunately, I don't have an immediate solution for these situations.
I recently purchased a UE32B6000 TV and I am having problems with the 'flashlight' effect in the bottom right hand corner.
I have been on the phone to Samsung UK support and they have been pretty helpful, however they don't seem to understand that it only happens in the one corner.
I have followed their instructions to change various settings and it looks fine on a black screen, but when there is an image on screen and the bottom right corner is black this is noticeable and distracting.
Hopefully Samsung HD Tech can help me out!