If you convert 4K 100mb footage to 1080p does it still contain 100mb of data?

Discussion in 'Panasonic Cameras' started by Duke Sweden, Aug 26, 2016.

  1. Duke Sweden

    Duke Sweden Mu-43 Regular

    Aug 9, 2016
    Duke Sweden
    This is just something that popped into my head. If you shoot 4K footage, say with a G7. We know the 4K footage is 100 mb per second. If I down res it to 1080p in Premiere Pro, does it still retain the 100 mb worth of data? Seems to me it would since everyone says that downrez'd 4K looks much better than 1080p from an HD camera.

    Ya think?
  2. tkbslc

    tkbslc Mu-43 Legend

    Simply, no. In the same way that if you export a still image at 2MP for web, it no longer has 16MP.
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  3. barry13

    barry13 Super Moderator; Photon Wrangler Subscribing Member

    Mar 7, 2014
    Southern California
    Also note there are at least several factors for compressed image/video quality:
    Resolution (4k, 1080, 16mp, ...)

    Codec or compression algorithm (PNG, JPEG, h264, h265, mjpeg, ...)

    Compression factor/'quality'/bitrate, e.g. JPEG 1-99 quality, video bit rates, ...

    A good 1080p encoding can look better than a poor 4k.

    One reason for the perception is that a 4k video on YouTube looks better on your 1080p display than a 1080 video, but this is solely because YouTube over-compresses 1080 videos.
  4. Jonathan F/2

    Jonathan F/2 Mu-43 Hall of Famer

    Aug 10, 2011
    Los Angeles, USA
    So a 4k video converted to 1080p doesn't look better on screen versus a native 1080p video? Is the only advantage of 4k footage mainly for cropping if outputting to 1080p?
  5. barry13

    barry13 Super Moderator; Photon Wrangler Subscribing Member

    Mar 7, 2014
    Southern California
    If codecs are of sufficient quality, and sufficient bitrates, then they should look the same, or even the 1080 original may be better as it didn't have to be rescaled.

    Cropping is the only video advantage I am aware of, if you're never going to display at higher than 1080p.

    Stills extraction would have higher resolution, of course, from the 4k.
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  6. DanS

    DanS Mu-43 All-Pro

    Mar 8, 2016
    Central IL
    Down sampling from 4k to 1080p has the same advantages as down sampling a 16mp still to a 4mp one.
    Decreasing noise is a good example, as is cropping. However, like most things the devil is in the details.
  7. barry13

    barry13 Super Moderator; Photon Wrangler Subscribing Member

    Mar 7, 2014
    Southern California
    Good point about noise, but since the cameras are also down-sampling for 1080, would there be a difference?
  8. tkbslc

    tkbslc Mu-43 Legend

    Which is to say zero.

    It has the appearance of having less noise, but only because now you can't zoom in as far on the details (or noise).
    Last edited: Aug 27, 2016
  9. DanS

    DanS Mu-43 All-Pro

    Mar 8, 2016
    Central IL
    In post you usually have more processing power, and you definitely have more time, so you can run better algorithms than the camera can.

    Here are two clips I just took in my workshop with my G7 F/5.6 1/60 ISO 6400. These aren't that bad, but iv'e seen a lot worse.

    1080P direct from the camera at 20Mbps:

    4k down sampled to 1080P 20Mbps using ffmpeg:
    ffmpeg -i 4k.MP4 -c:v libx264 -preset slow -crf 18 -maxrate 20M -bufsize 20M -s:v 1920x1080 -sws_flags lanczos 4kDown.MP4

    why shoot 4k and then only deliver 1080P:
    1. The ability to reduce the appearance of noise
    2. cropping in post
    3. Stabilizing footage in post
    4. Panning in post
    5. zooming in post
    6. Shooting A & B roll at the same time

    The main reason not to shoot 4k is the cost/time ratio.
    1. more SD cards
    2. more HD space
    3. more processing power to post process at a reasonable rate.
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  10. D7k1

    D7k1 Mu-43 All-Pro Subscribing Member

    Nov 18, 2013
    Most 1080P does not have full 1080 resolution, yet when you down sample 4K you get full 1080. Big difference in quality.
  11. Bif

    Bif Mu-43 Top Veteran

    May 28, 2012
    San Angelo TX
    Bruce Foreman
    I shoot in 4K, edit in 4K (although I don't have a 4K display yet), then render to 1080p (mostly in MP4). I see a noticeable difference from footage shot, edited, and rendered all in 1080p. While edge outlines show no difference in sharpness, image tones in the footage shot in 4K have a more "solid" appearance to me, the overall look is a bit "richer" to my eye.
  12. DanS

    DanS Mu-43 All-Pro

    Mar 8, 2016
    Central IL
    my work flow is as follows:

    1. I shoot UHD/4K h264 at 100Mbps with my G7 (max bitrate).
    2. I down sample UHD to HD DNxHR SQ. DNxHR is much easier for an editor to handle real time.
    3. I edit in Davinci Resolve and then export HD DNxHR SQ
    4. The last step is to convert the DNxHR (#3) to whatever deliverable format i want, usually h264/mp4 for youtube.
    Shooting in 4k give me the flexibility to go back and tweak a shot if needed.