Here's a synchronisation of the three movies based on 2 events. 1) The appearance of the Cabell car just beneath the stop light at the top of Elm in Dorman & Weigman & 2) The dissapearance of the jfk limo under the underpass in Zapruder & Weigman . Frames from all 3 movies are taken at 1 second intervals. A vertical line crosses 3 frames taken at the same time, within perhaps a second either way :
Here's a synchronisation of the Zapruder & Dorman movies based on Z 255. The equivalent Dorman frame to Z 255 is calculated from the appearance of the trunk of the lbj ss car in Dorman, and an analysis of the Z 255 Altgens photo. Frames from both movies are taken at 1 second intervals. A vertical line crosses 2 frames taken at the same time, within perhaps a second either way :
The 'C' on the third frame of the Dorman movie marks the point 1/16 second after the Cabell car is seen there. Unfortunately taking only one frame per sixteen from that movie meant losing the more interesting frame.
Note the substantial agreement in the result, whichever way we attempt the synchronisation. In both cases, the motorbikr cop appearing at the end of the Dorman movie has still not started taking the corner onto Elm as Jackie gets back into her seat and the limo covers the last few yards before vanishing into the underpass.