Eigenface face recognition using opencv2.4.3

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I have implemented the eigenface recognition algorithm using opencv 2.4.3 as given in the "face recognition through opencv" tutorial.Although there are no errors in the code and it works fine-detects face,but it fails to perform recognition properly i.e. it shows prediction=-1 even for images in the database.I had initially used AT & T database available online and later made database of my own images but still in both cases it fails proper recognition.What can be the reason for this?can the clarity of my own image database be the reason for this? please guide.