Hi, the only problem I can see is if you have a 4 x 4 array to make sure the shadow of your hand when you cover the LDRs in the centre of the array, you will have to choose your threshold well.
Also place a mask over the LDRs so that they have a window over each one,covering the window with your finger will then put the LDR in complete darkness, this will make sure you have a definite covered and uncovered in dull light transition.
Tom.... 