August 1, 2016 at 8:34PM

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4K noise reduction by downscaling it to 1080p

Hi everyone. I've been playing with 4K video since couple months now, i'm using DJI Osmo and Phantom 4. Thing that i want to ask is, is it true that i could reducing video noises by downscaling my 4K footage to 1080p project file (Premiere Pro)? I knew that DJI Osmo and Phantom only use 1/2.3 sensor size and the video quality is not as good as DSLR camera but 4K is 4K right?

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Yes, you will get less noise because you are averaging (statistically speaking) four pixels to one. You also can create 1080p 4:4:4 out of UHD material.

August 1, 2016 at 9:29PM

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Cary Knoop
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Note that when you reduce 4k to 1080p you also reduce the overall information present in the signal. So yes, you can reduce noise, but signal/noise ratio is very difficult to increase after the fact.

DaVinci Resolve Studio has great spatial and temporal NR.

August 2, 2016 at 7:37AM

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>>>Note that when you reduce 4k to 1080p you also reduce the overall information present in the signal.

...But you will be able to max out the amount of information stored in the 1080p format. Many video cameras only record 1000+ lines of detail when shooting 1080p video, where you can come close to the full resolution of the 1080p format when down rezzing 4K to 1080. ( the Canon Cxxx cameras do this internally by taking the 4K image and down rezzing it to 1080 when recording, so they easily achieve 1500+ lines of resolution in their 1080p video image )

Guy McLoughlin

August 2, 2016 at 11:24PM

Guy, by your logic one should reduce a mpeg stream not by half in both directions, but by 16-fold in both directions. That would allow each macroblock to be represented by a noise-free pixel. That would truly "max out" the resolution you could get from each pixel. But it would obviously reduce the signal down to 256x135, which is obviously not very exciting.

I bought a 50" 4k TV monitor for $600 last week. The reality of 4k displays is now. Downs calling to 1080p "just because" doesn't honor this new reality.

August 3, 2016 at 7:19AM

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>>>Guy, by your logic one should reduce a mpeg stream not by half in both directions, but by 16-fold in both directions.

Actually, it's not "my logic", it's common knowledge that most non-cine cameras ( DSLRs and Mirrorless cameras ) only record at about half of the actual resolution of the 1080p format.

Where some higher end cine cameras that use 4K or higher resolution sensor will down-scale their image data to create a 1080p image with 1,500 lines of horizontal resolution or higher. In theory it should be possible to produce a 1080p image with 1920 lines of horizontal resolution when downscaling from a 4K (or higher) image.

If you doubt my words, you can try it for yourself using a DSLR, Mirrorless, or traditional ENG style camera that is able to shoot 4K. Simply shoot something using one of these non-cine cameras in 4K and then again with their internal 1080p format, and then down-scale the 4K footage to 1080p in post using an editing CODEC like the free Cineform CODEC. ( one of the Cineform engineers commented on this topic a couple of years ago when the Panasonic GH4 camera first came out, and he also mentioned that you can turn 4K 4:2:0 footage into 1080p 4:4:4 footage by downscaling with the Cineform CODEC )

When comparing the down-scaled 4K ---> 1080p footage to the 1080p footage shot by your camera, you should see a noticeable resolution increase in the down-scaled 4K footage.

i.e. the downscaled footage should show 1500+ lines of detail, where the 1080p footage will show something in the range of 800 to 1,000 lines of detail.

August 11, 2016 at 6:44PM, Edited August 11, 6:45PM

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Guy McLoughlin
Video Producer
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I really do not feel like arguing this, finding 1080p 4:4:4: better quality than the original 4k because throwing away 3/4 of information is not a problem because at least the color info is not thrown away does not even begin to make sense to me.

I have a 4k 4:4:4 display, and I make 4k videos and it is more than obvious that 4k 4:2:0 is far better than 1080p, 4:4:4 or not!

September 7, 2016 at 8:23PM, Edited September 7, 8:24PM

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Cary Knoop
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It's not that "obvious" at all. Resolution is only ONE aspect of images, color information, contrast, etc is another. If you can trade noisy resolution for clearer color information and less distractive noise, that's a big plus.

And you can blow 1080p to cinema size screen (I know cause I have, and in fact, Philip Bloom has also done that, at the Skywalker ILM studios as a showcase) and it will be totally fine quality wise.

Jackie Loggan

October 11, 2016 at 11:49AM, Edited October 11, 11:49AM

Hello, I have one question here.
So why the C100 doesnt give 4:4:4 since its 4K sensor down to 1080P?

May 3, 2017 at 10:28AM

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Rh Oudom
Director / DoP / VFX
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