The HF100 (and, I assume, also the HF10, but since I don't have one, I can only assume,) record in the AVCHD format.
AVCHD is based on MPEG-4, and is essentially the same codec as H.264 that Apple is so fond of. (In fact, AVC is just another name for H.264.) But, the "AVCHD" camcorder format stores the files in the same manner as Blu-ray discs; not as one single file per video.
The raw AVCHD files are recorded in either 1440x1080 anamorphic (anything but the highest quality setting,) or 1920x1080 "true" HD (at the highest quality setting.) When recording in the highest quality setting, the files are real 1920x1080 files.
You also have three frame rates to choose from. 60i, 30p, and 24p. Again, the raw AVCHD files are really those framerates. In 60i, you are technically getting sixty 1920 by 540 pixel interlaced 'fields' per second; with every other field offset by half a vertical pixel. This means that for every two fields, you get the equivalent of 1080 pixels. This is what conventional "standard def" TV has done forever. This is what broadcast digital 1080 does. At 30p or 24p, you get a full 1920x1080 pixel frame, 30 or 24 frames per second.
60i is better for fast-motion stuff, where you want the maximum motion detail captures; while the lower frame rates are better for slower-moving stuff, where you want more raw picture detail in trade for motion detail. In addition, the 30p and 24p settings allow for better low-light performance.
Caveat: There is no Mac OS X-native software that can natively edit AVCHD. iMovie, Final Cut Express, and Final Cut Pro all transcode your AVCHD into Apple Intermediate Codec when you import it. Not only does this import process take a while (on my 2.0 GHz MacBook Pro, it takes about 1.5x real time; so a 30 second clip takes about 45 seconds to import,) but the AIC file is about ten times bigger than the original AVCHD file; and it also forces your video to 1440x1080 anamorphic at 60 interlaced fields per second! AKA: It is worthless to record in anything other than 1440x1080/60i. I *REALLY* hope Apple supports at minimum importing at the full quality; and even better, native AVCHD importing, soon.
What I would really like is if it were to quickly import the original AVCHD, maybe re-wrap the raw audio and video data into a single conventional MPEG-4 or QuickTime container file, then only convert the sections to AIC that you actually make edits to. Even better, don't actually perform any edits at all; just "recompile" the finished movie when you publish it. Transcode from AVCHD to AIC, perform modifications to AIC, then transcode back to "Apple H.264" for export. Make all of the transcoding part of the finalize process; not the import process.
For Final Cut, retaining the ability to transcode to AIC on import would make sense; but not for iMovie. iMovie should just do all the coding at the end. Maybe generate a low-resolution "preview" movie file for you to see while making the edits; but save all the heavy-lifting for the end. (As you can tell, importing is my pet peeve. I figured that moving to a random-access flash-based storage medium would make imports much faster than importing from tape. I was wrong.)
