Another way of understanding the Breit frame is to look at the elastic scattering A + γ γ → → A ′ . The Breit frame is defined as the frame in which p → → A + p → → A ′ = 0 . There are different occasions when Breit frame can be useful, e.g., in measuring the electromagnetic form factor of a hadron, A is the scattered hadron; while for deep inelastic scattering process, the elastically scattered parton should be considered as A . It is only in the latter case the Breit frame gets related to infinite-momentum frame.