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Have you try to crop P3P's 4k video in post?

Discussion in 'Pro/Adv Discussion' started by Kevin Shi, Aug 8, 2015.

  1. Kevin Shi

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    One of the key advantages of 4k is that you can crop in post processing, and in theory if you crop 4k to 1080p, it should have similar video quality as you shoot in 1080p. But actually it's not the case, when i crop 4k to 1080p, or even to 2.7k, and then output the video as 1080p, the footage is very very muddy.

    is this the same for you guys?
     
  2. rjbrown7

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    I use Premier pro cc and have had great results editing on 4K timeline and outputting to 1080p. I can scale and frame footage with minimal quality drop off. Only problem is its a little slower working with the 4k files.
     
  3. JimM

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    I use Magix Video Pro X7 and also found that when choosing 'Export Movie' using HD values it was lower quality than I expected.
    I used 'Export to device' and chose HD quality to PC and the quality is superb!

    Other editors may show similar behaviour.
     
    #3 JimM, Aug 8, 2015
    Last edited: Aug 8, 2015
  4. 4wd

    4wd

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    This is shot at 4K then exported at 1080p with some sections cropped to 'zoom in'.
    You can tell, but probably wouldn't have noticed normally.
    Adobe premiere

     
  5. Kevin Shi

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    would you mind sharing a 4k video and cropped 1080p video?

    I didn't the experiment again, as follow:
    A. Shoot 4k, no crop, output 1080p (downscale, but maintain picture frame)
    B. Shoot 4k, crop to 2.7k, output 1080p (zoom)
    C. Shoot 4k, crop 1080p, output 1080p (zoom again)
    D. Shoot 1080p

    result (video quality):
    1. A > D
    2. B ~= D
    3. C < D

    B and C look like using a point & shoot camera and use software zoom.
     
    #5 Kevin Shi, Aug 8, 2015
    Last edited: Aug 8, 2015
  6. Kevin Shi

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    Thanks, 4wd.
    How much did you zoom in?
    Crop 4k 25% to 1080p and output 1080p just seems unusable to me.
     
  7. 4wd

    4wd

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    I forget now, the main thing was to be aware of aspect ratio.
    I did a manual calculation to get it right!
    Probably about 50% I guess.
     
  8. Kevin Shi

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    1080p@30 bit rate is 28, 4k@30 bit rate is 59.
    Which means 4 times resolution, but about twice data rate.
    It seems you just can't zoom in too much without hurting video quality.
     
    Nannerz likes this.