Facial recognition techniques

I've been wondering how face recognition algorithms work. This news article puts a name on some of them. For future reference.

"The two main techniques used to recognise faces electronically are principal-component analysis (PCA) and linear-discriminant analysis (LDA). Both compare a picture of someone’s phizog with a reference image taken in a controlled environment. Passport photos and mugshots, then, are about as ideal as it gets."

Source:
http://www.economist.com/news/science-and-technology/21613160-facial-recognition-systems-are-getting-better-clocking-peoples-clocks?fsrc=rss%7Csct