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Calling all colourists - Grade Panasonic GH4 4K ProRes next to Arri Alexa 2K ProRes

Andrew Reid

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We had a studio that shall go nameless (but the name rhymes with Disney) once deliver footage to us as 8bit prores! So we "had" to work with it.. it took maybe 10x the amount of work because you can't camera track, planar track, color key, degrain.. it's just wrecked once it goes to 8bit. 


I'm sorry but WHAT? You can do a camera track on 8-bit data. You can planar track, color key, degrain, none of them require more than 8-bits. They only require that the image otherwise is good.


Are you confusing some other elements of the image?

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not literally "can't".. hmcindie, it took us around 10x (honest estimate) to do what we had to do because the footage was terrible. it's wasn't all due to the 8bit issue, but we were working with film that was not only old, we had an 8bit prores copy, it made our lives very difficult.


i'm working on a show right now, it's in season 6, i've been working on it since season 1.. every roto is unique and floats off target, the track is just a starting point, there's always a lot of manual work, there is nothing you "can't" do.. that's just hyperbole.


a clear example of a problem with keying with 8bit is with fine hair, that is when you really need the extra dynamic range.

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Here's a quick-and-dirty GH4 downscaler app for Mac I wrote that will sum four luma samples and write each frame as a 10 bit, 2K DPX file:




There's no GUI, so you'll need to run it from the terminal. It's very easy. You just type this:


It'll spit the numbered DPX frames out in a folder named "dpx_out."


I'd like to know if this really does offer an advantage, or if it's just wishful thinking...

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  • 1 year later...

My dear colleagues,

I really need your input on the following subject.

  • I own an 21.5 inch iMac since 2011( i know its been a really long time... i should upgrade...)
  • Processor  2.5 ghz intel core i5
  • Memory 4gb 1333 Mhz DDR3
  • Graphics AMD Radeon HD 6750M 512 MB

 Now that i am shooting 4K (4096.2160) at 100mbps with GH4 , i am using the following workflow.

  • Using Apple's Compressor, i transcode all the 4K MOVS to Apple Pro Res 422 (HQ) 
  • Import them in FCP7 and start editing.

So far so good, but having only a 512 MB Graphics card i am now facing difficulties in the grading process.

Davinchi Resolve is constantly dropping at the 1920.1080p Apple Pro Res 422 HQ xml export from FCP7.

In addition when trying to reduce the Davinchi's timeline resolution i have to do it drastically so i can colour correct or apply any LUT.

I am trying different ways to solve this but i need your insight in this one.

Last but least, i am trying to avoid conforming all the 4K MOVS to a 1080p MOV (using a H264 codec).  

I need to find a workaround , cause of the VLOG and LUT packages i am planning to buy and explore soon enough.

Hope i can make things work with my old time iMac machine :)


Petros Goritsas

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