Sorry, another post on that all that and bag of candy corn gem Trick 'r Treat. Anyone whose bought the DVD (if not, buy it now sucker...backordered on Amazon, hehehe) knows the disc features both 2.39:1 widescreen and full screen presentations. The film was shot using Super35, meaning the entire 35mm frame captures image information. This "big square" of picture per frame gives filmmakers the ability to freely move the widescreen matting about the frame to their whim to capture their perfect composition, instead of having what was shot "hard set" without some strange trickery to shift the framing.
This also benefits re-formatting a presentation to "full screen" by having the ability to "open up" the frame by removing the matte bars, but the preferred framing is still severely compromised since the Super35 frame is so huge it captures unwanted things like dead space, boom mics, grips, wires, and lighting rigs. So it's not simply a question of just removing the widescreen bars. This is the case with Trick 'r Treat, with the full screen option ruining the memorable imagery.
So here's some captures comparing the widescreen and full screen presentations. Use these when your aunt or more dimwitted buds come over on Halloween and ask you why you picked the widescreen option. Also irritating is the fact Warner chose to do this to begin with. Whenever you see wide and full versions on one DVD it means the film is encoded twice on one dual layer disc with each encode taking up an entire layer. This hampers the potential image and audio quality of the widescreen version and limits the extra features that can be included without going to a 2-DVD set. This needless space issue is presumably the reason why the Blu-ray edition has more supplements like a commentary, making-of, and additional scenes.
Also I noticed another small detail I hadn't before, over her shoulder: