▁uses ▁an ▁array ▁of ▁photos ites ▁that ▁consist ▁of ▁three ▁vert ically ▁stack ed ▁phot odi odes , ▁organized ▁in ▁a ▁two - dimensional ▁grid . ▁Because ▁different ▁w avel ength s ▁of ▁light ▁pen et rate ▁sil icon ▁at ▁different ▁depth s , ▁each ▁of ▁the ▁three ▁stack ed ▁phot odi odes ▁has ▁a ▁different ▁spectral ▁sens itivity ▁curve , ▁allowing ▁it ▁to ▁respond ▁to ▁different ▁w avel ength s . ▁The ▁signals ▁from ▁the ▁three ▁phot odi odes ▁are ▁then ▁processed , ▁resulting ▁in ▁add itive ▁data ▁for ▁the ▁three ▁primary ▁colors : ▁red , ▁green , ▁and ▁blue ▁( RGB ). ▁ ▁The ▁X 3 ▁sensor ▁technology ▁was ▁first ▁deployed ▁in ▁ 2 0 0 2 ▁in ▁the ▁S igma ▁SD 9 ▁D SL R ▁camera , ▁and ▁subsequently ▁in ▁the ▁SD 1 0 , ▁SD 1 4 , ▁SD 1 5 , ▁SD 1 ▁( including ▁SD 1 ▁M err ill ), ▁the ▁compact ▁S igma ▁D P 2 ▁series ▁from ▁ 2 0 1 2 , ▁the ▁S igma ▁d p 2 ▁Qu attro ▁series ▁from ▁ 2 0 1 4 , ▁and ▁the ▁S igma ▁SD ▁Qu attro ▁series ▁from ▁ 2 0 1 6 . ▁The ▁development ▁of ▁the ▁F ove on ▁X 3 ▁technology ▁is ▁the ▁subject ▁of ▁the ▁ 2 0 0 5 ▁book , ▁The ▁Sil icon ▁E ye ▁by ▁George ▁G ilder . ▁ ▁Operation ▁ ▁The ▁diagram ▁to ▁the ▁right ▁dep ict s ▁how ▁the ▁F ove on ▁X 3 ▁sensor