Front facing camera on S7 giving dark pictures

[AC Question]

Yesterday when taking a selfie of me and my daughter the preview pic in the corner showed up Normal, but when I went in to the gallery to view the picture it was way dark. Took a selfie of us on Snapchat camera and it turned out fine. Anybody know what I can do to fix this problem?? I'm not sure how to upload a pic here or if show what was going on.