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GH2 Video Mode 24 fps, 29.97 fps, vs. 59.94 fps

Discussion in 'Filmmaking' started by uscrx, Oct 18, 2015.

  1. uscrx

    uscrx Mu-43 Veteran

    440
    Aug 26, 2011
    Shasta Cascade
    So I have been recording my son's flag football games...just by an accident, I used AVCHD 720p in S mode at 1/125 second shutter speed. The file showed 59.94 fps.

    I rendered the video in Vegas Pro 13. Many frames in 50% slow motion. The video looked really good.

    Then I started reading...how 24 fps gives the most natural look etc. So I filmed the game in Movie mode at 24 fps. My goodness...I spend hours trying to render the video to look smooth... and when I finally did, it was really hard to watch. 29 fps wasn't much better.

    What is the fascination with 24 fps?
     
  2. jackalope

    jackalope Mu-43 Rookie

    21
    Mar 8, 2016
    24fps happens to be the framerate of film but it's not more natural or more smooth.

    First of all, a high framerate is good for sports because it's fast action, and you get the benefit of being able to slow it down too.

    But 24fps also makes no sense for viewing on a TV or computer monitor because these devices refresh at 60fps. In order to display 24fps they must do telecine conversion where some frames are displayed for 3 refreshes, and some for 2 refreshes. That makes the video uneven. There is no reason to shoot 24fps unless your video will be viewed with a movie theatre projector.
     
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  3. uscrx

    uscrx Mu-43 Veteran

    440
    Aug 26, 2011
    Shasta Cascade
    Thank you for the response. This is valuable.
     
  4. kevinparis

    kevinparis Cantankerous Scotsman

    Feb 12, 2010
    Gent, Belgium
    Not true... refresh rate and frames per second are different things. In the days of analogue display devices refresh rates used to be related to the frequency of the local mains electricity... 60Hz in the US and 50Hz in Europe.

    K
     
  5. jackalope

    jackalope Mu-43 Rookie

    21
    Mar 8, 2016
    They aren't unrelated things. The screen refreshes 60 times per second. It has to fit 24 frames into those 60 refreshes. Some frames it has to display 2x and some it has to display 3x. With 30fps it just displays each frame twice.

    That's why 120hz TVs were invented, so that 24fps movies could be played with each frame displayed 5 times.
     
  6. AerialFilm1

    AerialFilm1 Mu-43 Regular

    69
    Sep 15, 2012
    Wekiva, Florida
    Google Frame Rate vs. Field Rate. Creative Cow has several different ways of explaining this. They explain it much better than I could. It's actually so simple it goes right by most people the first hundred times, including myself.
     
  7. jackalope

    jackalope Mu-43 Rookie

    21
    Mar 8, 2016
    No need to Google-- It's called telecine. What I described is exactly what happens. It's why playing 24fps video on a 60hz screen creates "judder". 30fps is better for 60hz monitors because it evenly divides. Very simple! :2thumbs:
     
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  8. JDS

    JDS Mu-43 Regular

    60
    Nov 11, 2014
    San Francisco, CA
    Isn't shutter speed much more important than refresh rate? Shooting at 1/50 sec will do a ton more to smooth the video than switching from 24fps to 30fps, right? Kind of a newbie at this, but I would guess it's shutter speed that makes the video look bad more than anything. Movies look just fine on HDTVs, even with a mismatch on frame rates. I believe that's what the kevinparis video speaks about, haven't had a chance to watch it yet.
     
  9. JDS

    JDS Mu-43 Regular

    60
    Nov 11, 2014
    San Francisco, CA
    By the way, I'm very interested in this as I have a GH2 set up specifically for video, and haven't had much of a chance to play with it yet.
     
  10. jackalope

    jackalope Mu-43 Rookie

    21
    Mar 8, 2016
    IMO the main reason for 30fps is just that it evenly divides into what the vast majority of screens display, including computers, phones, etc. But it should be a little smoother just like 48fps is smoother on a 48fps projector than 24p

    But I don't see why you can't shoot at 1/50 with 30fps. The shutter speed being half the length of a frame is just an old timey convention from film mechanisms
     
  11. JDS

    JDS Mu-43 Regular

    60
    Nov 11, 2014
    San Francisco, CA
    I may be wrong, but I don't think it has anything to do with film. You need an appropriate amount of motion blur to make the video look good, and so if the OP was using too high a shutter speed that would affect the video quality of the 24fps shot much more than the 60fps, if I understand it correctly.
     
  12. jackalope

    jackalope Mu-43 Rookie

    21
    Mar 8, 2016
    Last edited: Mar 10, 2016
  13. jackalope

    jackalope Mu-43 Rookie

    21
    Mar 8, 2016
    I mean the shutter being exactly half is because of the film camera shutter mechanism, it's a disc that's half covered and half open and it spins

    You can use whatever shutter speed the camera will support

    What I've figured out is too much motion blur makes stabilization impossible, because you get blur not just from subject movement and panning, but also your own shaky hands. So you need a high enough shutter speed to prevent shaky-hands-blur if you're doing postprocessing stabilization
     
  14. jackalope

    jackalope Mu-43 Rookie

    21
    Mar 8, 2016
    Last edited: Mar 10, 2016
  15. JDS

    JDS Mu-43 Regular

    60
    Nov 11, 2014
    San Francisco, CA
  16. kevinparis

    kevinparis Cantankerous Scotsman

    Feb 12, 2010
    Gent, Belgium
  17. jackalope

    jackalope Mu-43 Rookie

    21
    Mar 8, 2016
    You're right, you can see the positions of the bird

    But would it be better if it was just a blur across the screen?

    Can you see any strobing with the bird swimming at slow speed?
     
    Last edited: Mar 10, 2016
  18. kevinparis

    kevinparis Cantankerous Scotsman

    Feb 12, 2010
    Gent, Belgium
    Possibly yes... as it wouldn't distract from the main subject.

    couple of things to highlight

    1) 60hz refresh and 30 fps is predominantly a North American standard... most of the rest of the world works to a 50Hz/25 fps standard.

    2) The shutter speed to frame rate ratio is kind of crucial... You need to understand that before anything else... yes you can deviate from the rule... but you have to understand it first

    3) our eyes work in odd ways :)

    K
     
  19. jackalope

    jackalope Mu-43 Rookie

    21
    Mar 8, 2016
    It seems like people don't understand the rules though... For example they claim 24p is the best without taking into consideration that display is almost always on 60p monitors. Or that exposure time should always be 1/2 the length of a frame even if the motion blur makes stabilization impossible
     
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