This paper explores the diffraction region between thin and thick holograms, commonly referred to as the transition region. The VOHIL model is used to assess the internal interference conditions along a specified diffraction direction. We examine the maximum phase difference between the two endpoints of the hologram for both the +1st-order and -1st-order diffractions through internal interference. This analysis leads to a criterion that aligns with the Klein parameter. Additionally, a new parameter, the de-phase factor, is introduced to assess the feasibility of diffraction along a chosen direction from a whole-field perspective. The variation of the de-phase factor in the -1st-order diffraction is slower compared to other directions, except for the +1st-order diffraction, owing to the natural existence of the -1st-order diffraction at every tiny hologram unit. The primary way to stop the -1st-order diffraction is by adjusting the thickness if the incident angle is fixed. Thus, examining the -1st-order diffraction is an effective way to check if a hologram is under the Bragg condition. Although rigorous simulation methods, such as rigorous coupled-wave analysis, can provide more precise results, the proposed analysis scheme, based on the VOHIL model, offers valuable physical insights into these characteristics.