Can anyone tell me the name of this horror movie I saw as a kid?

Question

I believe the movie was on TV around the early to mid 1980s it was about a girl who discovers her sister is a witch, the only scene I remember well is when she is in a dark room developing pictures of her sister and I think she discovers her sister is always wearing sunglasses to protect her eyes from camera flashes.

Answer 1

...sounds very much like a late 70's T.V. movie, directed by Wes Craven, of all people, and called, "Stranger in Our House" (aka "Summer of Fear")...

Linda Blair plays a young teenager, named Rachel, I think, living with her family on a ranch; a very beautiful and distant cousin comes to live with them, after the mysterious death of her parents. Rachel begins to observe that her cousin engages in very mysterious and covert practices, which appear to have an almost supernaturally hypnotic and irrestible effect on her family, who of course, refuse to believe Rachel, when she raises her concerns. When Rachel suddenly realizes that her cousin might be practiced in witchcraft, she confronts her, who then threatens to hurt her family, if she prys any further...

...through the help of someone totally unexpected, living in town, and also skilled in witchcraft, Rachel decides to fight fire with fire, studies the craft, hones her own psychic abilities, and takes on her cousin, herself...

Wes Craven did this one, just after "The Hills Have Eyes", and just short of "Deadly Blessing" and "Swamp Thing"...

...check it out, here!!!