▁components ▁that ▁includes ▁only ▁scalar ▁( i . e . ▁not ▁magnetic ) ▁fields ▁will ▁be ▁exactly ▁equivalent ▁if ▁the ▁electron ▁source ▁and ▁observation ▁point ▁are ▁revers ed . ▁ ▁In ▁a ▁T EM , ▁elect romagnet ic ▁l enses ▁have ▁been ▁shown ▁not ▁to ▁inter f ere ▁notice ably ▁with ▁observations ▁of ▁reci pro city , ▁provided ▁that ▁el astic ▁scatter ing ▁processes ▁domin ate ▁in ▁the ▁sample ▁and ▁the ▁sample ▁is ▁not ▁strongly ▁magnetic . ▁Care ful ▁application ▁of ▁the ▁reci pro city ▁theorem ▁in ▁cases ▁where ▁it ▁is ▁valid ▁give ▁a ▁T EM ▁user ▁considerable ▁flex ibility ▁in ▁taking ▁and ▁interpre ting ▁images ▁and ▁electron ▁diff raction ▁patterns . ▁Re ci pro city ▁may ▁also ▁be ▁used ▁to ▁understand ▁sc anning ▁transmission ▁electron ▁micro sc opy ▁( ST EM ) ▁in ▁the ▁familiar ▁context ▁of ▁T EM , ▁and ▁to ▁obtain ▁and ▁interpret ▁images ▁using ▁S TE M . ▁ ▁Display ▁& ▁Det ectors ▁ ▁The ▁key ▁factors ▁when ▁considering ▁electron ▁detection ▁include ▁Det ect ive ▁Quant um ▁E ffic iency ▁( D Q E ), ▁Point ▁Sp read ▁Function ▁( PS F ), ▁Mod ulation ▁Transfer ▁Function ▁( M TF ), ▁pixel ▁size ▁and ▁array ▁size , ▁noise , ▁data ▁read out ▁speed , ▁and ▁radiation ▁hard ness . ▁ ▁Im aging ▁systems ▁in ▁a ▁T EM ▁consist ▁of ▁a ▁ph osph or ▁screen , ▁which ▁may ▁be ▁made ▁of ▁fine ▁( 1 0 – 1 0 0   μ m ) ▁partic ulate ▁z inc ▁sul f ide