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  1. Hi yall

    Looking for the best workflow for handling videos shot with Sony HDR-CX130. This camera shoots 1080p 50p (PAL land), but strangely no 25p mode... (why??) Thinking I want to shoot and store raw material in best possible quality, I go for 50p.

    Then for playback (mostly from mediacenter PC) 50fps is not always practical, so I'm making 25p renders as well... Of course 50fps is very smooth on camera movements, and this will get lost when rendering to 25p. As others doing the same, I've tried:

    1) Just selecting every second frame. This was every frame is very sharp but the "film motion" effect is almost too strong camera movements are very "choppy".

    2) Blending pairs of frames (1+2 -> 1', 3+4 -> 2' etc). This reduces the film motion effect of course but the nice HD detail is sort of lost except when camera is very still.

    I am wondering... Is the camera choosing higher shutterspeeds knowing it's shooting 50fps, than it would had it had an 25fps mode ? To rephrase, would "true 25fps" be less film motion choppy by being able to use lower shutter speeds ? (thus making a "better" 25p than either of the two methods above).

    Or would a "true 25p" camera produce the same effect as 1) above ?

    Thanks in advance for your insights
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  2. Member Cornucopia's Avatar
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    Jeffboy,
    1st, I want to commend you for trying to capture & store the Highest quality that your camera can make.

    2nd, you say you have a MediacenterPC, but no specs - how capable is it? Much of this reworking might be thrown out if your PC could easily handle your originals.

    3rd, let's say you DO have to render - you don't mention what you're using, and this can (plus the algorithms chosen) can make all difference in the world.

    So, to answer your questions:

    Consumer camera shutter speed usually closely follows framerate in order to allow the most light. Pro cameras give you a choice, depending on the "look" you want, and other technical requirements.
    IOW, a framerate setting of 50fps on your camera is going to allow the shutter to be "open" for ~1/50th sec, whereas a framerate setting of 25fps is going to allow it to be "open" for ~1/25th sec. That's twice as long. This alows motion to "smear" and blur, which does give it a more natural quality.

    Is this like #1? NO. It would be much more like #2.
    #1 in your example is retaining the shorter exposure time, just "holding" that exposure for double the length. It is quite unnatural looking.

    If you can't handle 50p, you might be able to handle 50i. You could get this by taking the upper field from frame A + the lower field from frame B, upperC + lowerD, uE+lF, etc. This would MATCH what would be generated from a true 50i camera (in terms of framerate, shutterspeed, and motion quality).

    #2's formula shows exactly what you should expect to see with a 25p film. The HD detail IS lost during motion.

    Scott
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  3. True 25p is supposed to be "choppy." It's as choppy as 24p.

    If your movements weren't slow, controlled, and stabilized it will be choppy for 24p or 25p. That's normal.

    If we assume that the effect you are seeing is the higher shutter speed when shooting at 50p (and not normal "choppiness"), then a 3rd option is to add motion blur in post. This is not the same thing as a frame blend.
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  4. Thank you...

    The media PC is built around Intel core i3 and while it does handle 50p quick well in terms of cpu etc., there are some difficulties getting smooth playback in terms of vsync/framerate judder. This is difficult to achieve even with 25p but I have this working perfectly now (Reclock vsync control etc).

    These difficulties would be the same with 50i (since it's still presenting 50 frames/sec)

    And yes the choppiness is there for 25p, but how much it's perceived depends largely on the shutter/aperture (slower shutter speeds would give a natural motion blur to each frame lessening the choppy effect). But since each of those 50p are very sharp individually, the choppiness gets too much, it becomes annoying to watch.

    So... based on what you write, and the fact that this camera will never have shutter speeds long enough to produce natural motion blur, then probably it's best not to downconvert to 25p but just keep it in 50p and work on optimizing the playback...
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