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How are import resolution and export resolution related.

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Evan Stanfield
How are import resolution and export resolution related.
on Nov 29, 2017 at 8:05:12 pm
Last Edited By Evan Stanfield on Nov 29, 2017 at 8:14:32 pm

Thanks for reading!

About 2 years ago I was digitizing some beta footage into FCP via a kona card. While I was talking with one of the Avid guys he mentioned (or so as I recall) it was better to import in the highest res possible then export to the res you want. As opposed to importing at the res you want, and exporting at the same res.

Fast forward to now. I am getting ready to go into a production and the same question applies (with new tech though). Will filming in 4k, importing in 4k and exporting from FCP at HD look better or the same as filming in HD, importing in HD, and exporting in HD.

This leads me into a question about editing technique. Is there some sort of standard, or loose rule of thumb around how much you can zoom in FCPX before it degrades the quality of the image? For example, could I take footage shot in 1080 could I zoom from a long shot to a mid shot without losing too much definition?

I hope that makes sense, please let me know if I need to clarify anything thanks again!


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Joe Marler
Re: How are import resolution and export resolution related.
on Nov 29, 2017 at 10:40:37 pm

[Evan Stanfield] "Will filming in 4k, importing in 4k and exporting from FCP at HD look better or the same as filming in HD, importing in HD, and exporting in HD..."

With every other factor held constant, and if viewed on a large enough screen, filming in 4k and exporting at 1080 can look better than filming in 1080 and exporting in 1080. I say 1080 because technically 720p/60 is also HD by ATSC standards, and because ABC, Fox and ESPN broadcast exclusively in 720p/60 HD.

However there are many variables and it's easily possible to have better results shooting and exporting in 1080 vs 4k. If the 4k camera, lens, codec, lighting, cinematography or the distribution system to the final viewer is not good quality, then just using 1080 might be better. There are situations where 4k is just carrying around a lot of dead weight.

Another variation is if shooting 1080 on a camera optimized for 4k. In that case the 1080 image may be degraded vs. a camera designed specifically for 1080. E.g, my old Canon 5D Mark III shoots much better 1080 than my Sony A7RII, but the A7RII's 4k down sized to 1080p looks better (even in very low light) than the 5D3's native 1080p.

A good quality camera with a good lens that shoots 10-bit ProRes 4:4:4 at 1080p can look better than many consumer or even prosumer H264 8-bit 4k cameras.

However in many cases shooting 4k is a good idea, even if 8-bit 4:2:0 H264. If you don't crop it and export to ProRes, it will supposedly become true 1080p 10-bit 4:4:4 on output. See white paper by Barry Green "The Benefits of Shooting in 4k": ftp://ftp.panasonic.com/provideo/agdvx200pj/4kbenefits_techbrief.pdf

[Evan Stanfield] "...Is there some sort of standard, or loose rule of thumb around how much you can zoom in FCPX before it degrades the quality of the image? For example, could I take footage shot in 1080 could I zoom from a long shot to a mid shot without losing too much definition?"

If you assume the final viewer has 1080p resolution and the image is not degraded by encoding, UHD 4k can be zoomed 200% (using the FCPX scale factor) without losing effective resolution. If you are exporting 4k to 720 the limit is 300%.

If the original material is 1080p and the viewer is 1080p, you cannot zoom into this any without losing some quality. If the final viewer is using a smart phone via a streaming Youtube video, you might get away with a little zoom. In that case the viewer's effective resolution might be 720p or less.


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Brett Sherman
Re: How are import resolution and export resolution related.
on Nov 30, 2017 at 1:41:41 pm

[Evan Stanfield] "Fast forward to now. I am getting ready to go into a production and the same question applies (with new tech though). Will filming in 4k, importing in 4k and exporting from FCP at HD look better or the same as filming in HD, importing in HD, and exporting in HD."

Yes you will almost always get sharper images with less noise and compression artifacts by downsampling 4K to 1080p. But as mentioned, resolution isn't everything and different cameras look better or worse at 1080p. For example, I'd much rather be shooting on a Canon C100 MkII at 1080P than a Canon GX10 at 4K.

To bottom-line it, get the best camera you can, get 4K if you can swing it. Edit in 4K if your computer is up to the task. And export both 4K and HD.

--------------------------
Brett Sherman
One Man Band (If it's video related I'll do it!)
I work for an institution that probably does not want to be associated with my babblings here.


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vidda roshinns
Re: How are import resolution and export resolution related.
on Mar 20, 2018 at 3:18:56 pm

Slightly different topic.... Just for argument sake if i shoot in one codec render in a different codec and export to another seperate codec. If I shoot in MP4, render in pro res 422 and export back to pro res is the actual quality of the render the same as if i had shot in pro res to begin with?. I do not understand the chain of events with regard to the actual shooting to final export. There are three steps.... shooting rendering and exporting how do they relate/affect/alter any one of the three steps.


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Joe Marler
Re: How are import resolution and export resolution related.
on Mar 20, 2018 at 11:52:33 pm

[vidda roshinns] "if i shoot in one codec render in a different codec and export to another seperate codec. If I shoot in MP4, render in pro res 422 and export back to pro res is the actual quality of the render the same as if i had shot in pro res to begin with?"

FCPX generally renders the timeline using ProRes 422, although you can modify the project to use several other ProRes variants. So no matter what the acquisition codec or the export codec, the render codec is usually ProRes.

MP4 is a container format that frequently contains 8-bit 4:2:0 H264 material. ProRes is a codec family which supports at least 10 bits per color channel and various chroma sampling resolutions.

In many cases you don't decide to shoot in MP4 or ProRes, your camera supports one or the other. Sometimes a camera that records MP4 internally can record ProRes to an external recorder. Some higher-end cameras can record either ProRes or MP4 internally. Some cameras which don't record ProRes can nonetheless optionally record in higher bitrates, bit depths, chroma sampling, or can use a lower-compression or "intra frame" codec. Using these is a tradeoff of data management, workflow complications and evaluation of whether it makes a perceptible difference to the final viewer.

The recording bit depth and chroma sampling is determined by the camera, not by the codec. IOW adding a ProRes HDMI recorder to a low-end camera will not magically provide true 12-bit 4:4:4 4k recording. The camera's sensor, imaging pipeline and output logic determines what it can export.

So in most cases a lower-to-midrange camera will record MP4 and there's nothing you can do about it. In the edit phase FCPX renders in ProRes and your only non-ProRes option is uncompressed 10-bit 4:2:2; IMO there's no reason to use that. So up the the point of export, there is often no codec decision to make. You normally shoot at the best resolution, codec and bit rate your camera produces, but in low-to-midrange cameras this is often only a choice of bitrate.

Your export codec will be determined by your delivery requirements. If you are uploading to Youtube or Vimeo, unless your program length is very short it may be impractical to export to ProRes. Using an H264 output codec will save a lot of space and upload time, yet produce pretty good quality if the encoding bit rate is high enough. Exporting to HEVC/H265 is also becoming and option, which can cut upload size roughly in half while retaining the same quality. However it requires hardware acceleration (and software which harnesses that) to provide decent encoding performance.

If you are handing off material to a downstream editor or color finisher, you'd generally export in ProRes not a "long GOP" codec like H264. This isn't because ProRes makes it better but it avoids possible quality loss of re-encoding to a compressed codec. Also I think the most common long GOP versions of H264 only support 8 bit 4:2:0. There are intra-frame versions of H264 which support higher bit depths and chroma samplings but they are less common. To achieve the quality of ProRes requires an H264 variant which is encoded at nearly the same bit rate, so "turnovers" are often done using ProRes.

In general the image quality is "baked in" at acquisition time and transcoding to another codec will not improve that. Thus there's no reason to transcode to ProRes optimized media before editing in FCPX -- from an image quality standpoint. From a performance standpoint it could be beneficial.

However It is theoretically possible to transcode 4k 8-bit 4:2:0 H264 to true 1080p 10-bit 4:4:4 on output. Achieving this requires (1) Your rendering codec must be ProRes 4:4:4, (2) You don't crop the image during editing, and (2) You export to ProRes 4:4:4. That is one case where choice of rendering and output codec could make a positive difference. Whether that difference is visible to the final viewer on typical playback devices after distribution and upload encoding is another matter. See white paper by Barry Green "The Benefits of Shooting in 4k": ftp://ftp.panasonic.com/provideo/agdvx200pj/4kbenefits_techbrief.pdf


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