.img or .dmg? What's the difference?

Hi Mark:

Both of these files are image files.

Image files typically have names that end in .dmg (also called a UDIF format). The image files that end in .img are from an image format originally used in Mac OS 9.

Hope that helps a bit-
Sue

Hi Mark,

to start serious first, have a read here:
http://en.wikipedia.org/wiki/.dmg
http://en.wikipedia.org/wiki/.img

.. in the MacOsX world, an .img is normally an "image" (=copy) of a disk (as dvd or cd), done e.g. with iDVD; the .dmg (which translates as "disk image"...) is in many cases not the virtual copy of a whole disk, but in many cases contains a folder with lots of stuff (to install, for instance)

so, iDVD creates .img - which later can be "mount" as "real" dvds...
context-menu should create .dmg.... which also can be mounted....

ahhhh, it's confusing!

BUT...

...saved as a disc image in disc utility (to save space)..... that is mostly nonsense, because video IS allready highly compressed... you probably save a few bytes... I would let out that step.

Hi Mark,

... ehm.... me alien, me no good english.... wott??
because, I don't understand your question/workflow, I discribe you mine...:

* iMovie projects: contain all clips PLUS all transitions, text etc EDITABLE; look like a folder with a star on; huge files; only to be saved on harddrives (I own a few)
* iMovie movies: final product of a iMproject; created using the export/share command in iM; export to tape or to iDVD>>creating a videoDVD.... DVDs are end-of-the-road, cannot (simply) been imported into iM; not editable, e.g. I cannot change a title within an exported movie....
* iDVD: videoDVD authoring tool; imports iMprojects; creates dvd-r or an image (.img) of a dvd-r; .img can be stored on harddrive; .img can be mounted to watch movie; .img can be burned with Toast to create video-dvd-r

I do backups of project onto hd, because they are too large to fit onto a dataDVD; I don't use any compressors or context menus to create a diskimage, because Mac's Finder offer the simple use of "drag'n drop" to copy files/folders/pkgs from drive to drive to media...

hope you find any of my rant useful for your problem... <still scratching head, booking new english lessons>

why not save a copy of the movie as a complete thing and NOT a .dmg file

A DVD disc is written in UDF format - while Mac hard drives are in Mac OS Extended format. Saving a DVD as a disk image .dgm file preserves the UDF file structure. When the .dmg file is written to writable media with Apple's Disk Utility you get a UDF format disc that will play in DVD players.