I shoot home video in HDV, and use iMovie HD to convert it to an
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TV compatible file (using the
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TV preset in iMovie).
For a fast action shot like shooting a basketball game (lots of side to side panning), 1.09 hours of HDV footage resulted in a 1.88 GB
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TV file.
A 34 minute HDV video with very little panning (camera on tripod) resulted in a 950 Mb
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TV file.
Other conversions seemed to follow along these lines.
As to where to the keep the file, if you mean the converted file, I suggest buying a big firewire drive (if you don't have big internal storage space) and putting it plus any other
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TV DVD conversions on that drive. By "big", I'm referring to Gb, not Mb.
If you meant where to store the iMovie file, you'll never have enough space for those (buy the most storage you can get). For example, that 1.88 GB
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TV file referenced above is rendered from a 58.42Gb iMovie file. That 950Mb
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TV file is rendered from a 22.26Gb iMovie file.
HD footage takes up a lot of space when imported. And since it is shot at a resolution beyond what the current
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TV can fully render, you'll likely want to keep it so that you can re-render it when a 1080i/1080p
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TV platform comes along (maybe someday).
I don't shoot a lot of home video, but I've already got a little of 1 Gb of iMovie imports on disc.
Lastly, regarding which camcorder, that is a very tough question to answer without the old "list the features important to you" type feedback. I'm about to switch from HDV to AVC, though all of the manufacturers seem to be purposely holding back from taking full advantage of AVC (presumably to protect the higher margin sales of their professional equipment).
As is, there is much online documentation and reviews (griping) that current AVC camcorders only yield about the same picture quality as the older HDV format (albeit in smaller file sizes). What many HD enthusiasts seem to want though is to crank up the AVC quality capture to the max (for maximum quality of picture) even if the file size ends up the same or larger than HDV file sizes. I'm certainly in this camp, as I subscribe to the idea that you only have now to capture family memories, and it would be better to sacrifice some cheap hard drive space for greater picture quality rather than saving hard drive space but getting only the same picture quality (as HDV).
Nevertheless, none of the manufacturers seem to want to take a big step in that direction, so stepping up to HD recording "as is" is better than sticking with SD until they finally get forced there. Most of the newest AVC camcorders shown at 2008 CES are just coming available. I'm favoring the Sony HDR-SR 12 or 11 for (most) features that matter to me (though I'm really disappointed that it is set to only record at 16Mbps when the AVC format max is around 24-25).