Saying no HUD means the pics "could" have been pre-rendered is fine, but then you went on to say that "some/a lot of these are" which is false (that's why I bolded it). None of these are pre-rendered, they're all pics taken by gamers and posted on the internet.
Wikipedia:
Halo 3 has a feature called Saved Films. This feature allows players to save a copy of the game data of a multiplayer match or campaign session to their Xbox 360's hard drive, so that they may watch it later on.
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Players are able to view the action from almost any angle and any player's perspective (including a free-roaming camera), as well as being able to slow down the speed and also play the recording in reverse. The Saved Films can even be edited in game to create a shorter clip of a particularly amazing or special moment. Players can also use the tool to take still pictures from films and upload them to the Bungie website.
As the Saved Films are only the game data (not an actual video), this allows the file sizes to be relatively small. A recording for a typical "long" game is in the region of only 6 MB. Films are also be played back at whatever resolution the Xbox 360 is set to, regardless of the resolution at which the player was using at the time of the recording. All games are recreated in real-time on the Xbox 360 using the Halo 3 engine. This allows them to be shared amongst any other Xbox 360 without any compatibility issues because they all run off the same code. The Saved Films feature is described as an "excellent training aid" since players can gain valuable tactical insight into the strategies of other players by viewing the saved films. Alternatively, they could have a look at other games uploaded through the fileshare.
This feature will also facilitate the creation of machinima and other game-related videos, as well as give the creators of such videos advanced tools to enhance the quality of this medium. Video game montage creators can save games to the hard drive of their Xbox 360 console for later use, so they never have to miss a camera shot, while machinima directors and cinematographers will have expanded camera options, instead of having to resort to using a first-person, gameplay perspective.
We don't provide the 'easy to program for' console that they [developers] want, because 'easy to program for' means that anybody will be able to take advantage of pretty much what the hardware can do, so the question is what do you do for the rest of the nine and half years? It's a learning process. - SCEI president Kaz Hirai
It's a virus where you buy it and you play it with your friends and they're like, "Oh my God that's so cool, I'm gonna go buy it." So you stop playing it after two months, but they buy it and they stop playing it after two months but they've showed it to someone else who then go out and buy it and so on. Everyone I know bought one and nobody turns it on. - Epic Games president Mike Capps
We have a real culture of thrift. The goal that I had in bringing a lot of the packaged goods folks into Activision about 10 years ago was to take all the fun out of making video games. - Activision CEO Bobby Kotick
