Edit: From clues I gotten from the comments and also from SpiritFryer, I made some edits to my answer
Could it be....
I am a tool for improving portrait photography
Saying cheese to the camera
I'm half as valuable as salt
From SpiritFryer' answers, the word SALT is worth 4 points in scrabble, and ee is worth 2 points, half of it.
I am at home in many places, one of those is the exact middle of a popular dairy product
Cheese is a popular product in many homes.
I'm often considered the same if only half of me is present
Not too sure about this one. Could it be that when you pronounce cheese, it's similar to chese?