I would like to understand video specs better. I have been through the article on LL regarding the differences between HD, SD, etc., and I understand the basics but think I need to read more detail. It would help if someone could point me to a comprehensive primer (online or not). To me, video resolution numbers don't seem to mean the same thing that they do in still photography. It is as though they are "nominal" numbers or maybe they imply more than the resolution of a single frame taken as a still.
This is what is puzzling me at the moment. I shot a video on a SD camcorder, using the 16:9 wide screen option. Uploading and editing in iMovie9 went well. I then became confused when uploading to vimeo. I tried numerous size conversion options trying to understand when the vimeo reprocessing (after upload) would add black bars, but I could not detect a pattern. I then read through the vimeo forums and someone very helpful there had written that exporting in QuickTime using custom size 872 x 480 worked best for SD widescreen in vimeo. (Btw, I tried uploading various sizes of exported snippets to YouTube to figure out what worked best there, and never really found anything that worked well, but I gave up early.)
I don't understand why 872 x 480. It is not exactly 16 x 9, although sort of close. When I uploaded at a custom ratio of 16 x 9, I would get black bars. Is it just because SD widescreen is NOT 16 x 9? (Why wouldn't it be, since I presume it was invented to cater to widescreen TVs?)
Like I said, if you know of a comprehensive document that explains this stuff, that would be perfect. Thanks very much.