We're capturing live SD video to an older G4 running FCP 4.5. The video is going in via firewire (converted from a composite signal via a JVC BR-DV3000 deck) using the standard DV NTSC preset. It's fine and normal 4:3 when captured. We copy the video file (just the mov, not the FCP 4.5 project file) to a newer iMac running FCP 7.0.3 for editing/dvd authoring/etc. On the iMac, it's changed to widescreen in the Finder preview as well as when opened in FCP 7 and the anamorphic option is checked when right-clicking on it (in FCP's browser) and looking at its format. This option is not checked on the G4 before copying the file. Unchecking the anamorphic option corrects it, but it's extremely annoying as we do this frequently.
First, why is it being changed in this manner, and how can we prevent it in the future?