> What’s the best method?
This is kind of subjective but I feel that methods 3 is the best because shooting good 24p is not easy and shooting 60i and converting to 24p later may cause surprises. Fast pans can become very jerky in 24p. You need to pan very slowly and deliberately. Try shooting 24p while panning across a picket fence to see what I mean. Method 3 will show you any problems in the viewfinder because you will be shooting 24p (60i will not).
It is also important to edit on a 24p timeline. You don’t want to be adding dissolves and generated media at 60i and then having them reduced to 24p. You may get undesired ghosting as Vegas interpolates frames. Keeping the project in 24p from the start ensures that what you see (and more importantly what you cut) is what you get.
Having said that… some people use method 1 and like the results which is why I said it’s subjective.
> if all clips are digital, what’s the difference between them ?
The 60i media will have frames that will need to be removed to get to 24p (leaving out the fact that one format is interlaced while the other is not). The removal of these frames may cause unwanted blended frames.
> and if Vegas can convert to 24P why bother shooting 24P ??
Because you want your original frames to be unblended and your camera motion to not be jerky by moving faster than 24p can capture smoothly. It takes practice to shoot good 24p.
> Is it really true that 24P DVDs are “smaller” in file sizes allowing you to “push” more quality (bitrate) on disc ??
Yes, for NTSC they have 6 less frames per second which results in smaller file size. You still can’t push the data rate above the 9Mbps limit but on a long movie you can get more on a disc at a higher rate than 60i could fit. (not such a big difference for 50i which is only 1 frame less)
~jr
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