Blackmagic Forum

I have a green screen shoot coming up with an Alexa 35, open gate, Atlas Orion .
Can anyone point me to some GS sample footage...or share a few frames..or advice..

Arri recommends shooting Arriraw linear, not log. I'd like to try keying a sample in Resolve before the shoot

David

David Cherniack wrote:Arri recommends shooting Arriraw linear, not log. I'd like to try keying a sample in Resolve before the shoot

Arriraw linear? Arriraw is 18 bit linear data which is log encoded to 13 bit data. Raw data doesn't have a necessary transfer function, it can be debayered to Log C4, linear, 709, 2100, whatever. The log compression of data is a process separate from the log debayer.

Sample footage, including 13 bit Arriraw, can be found here, no GS footage though.

https://www.arri.com/en/learn-help/lear ... ence-image

Good Luck

There’s no such thing as Arri Linear.

Arriraw is intrinsically log encoded.

You can of course transform to work linear in Resolve.

JB

John Brawley wrote:There’s no such thing as Arri Linear.

Arriraw is intrinsically log encoded.

You can of course transform to work linear in Resolve.

JB

Yep. Thanks. There was confusion on my part when I read on the Arri site https://www.arri.com/en/learn-help/learn-help-camera-system/image-science/vfx-faq:

"Our cameras offer three different encodings of the recorded image:

Linear encoding
Logarithmic encoding
Display-ready video encoding for Rec 709 monitors.

While ARRIRAW is encoded as linear data..."

On the same page they recommend shooting GS in Arriraw so hence my assumption that Arriraw clips in Resolve will come in linear.

Interestingly, in Resolve 19b4 Davinci YRGB Color Managed seems to provide better default color balanced transform to 709 of Alexa 35 than ACES cct. Anyone else had experience with Arriraw Alexa 35 material?

David Cherniack wrote:Anyone else had experience with Arriraw Alexa 35 material?

I don't fully understand your concern. Shooting greenscreen on different camera's doesn't make the workflow or considerations any different. It doesn't matter which camera you pick. Shooting raw as uncompressed as possible is always preferred. Any step down is going to be primairily a consideration of filesize management. ProRes 4444 (non XQ) is still going to work fine for most projects I'd say which is the lowest possible recording option on the 35 due to LogC4 needing higher bit depth. But for greenscreen you want 444 sampling anyway.

David Cherniack wrote:

John Brawley wrote:There’s no such thing as Arri Linear.

Arriraw is intrinsically log encoded.

You can of course transform to work linear in Resolve.

JB

Yep. Thanks. There was confusion on my part when I read on the Arri site https://www.arri.com/en/learn-help/learn-help-camera-system/image-science/vfx-faq:

"Our cameras offer three different encodings of the recorded image:

Linear encoding
Logarithmic encoding
Display-ready video encoding for Rec 709 monitors.

While ARRIRAW is encoded as linear data..."

On the same page they recommend shooting GS in Arriraw so hence my assumption that Arriraw clips in Resolve will come in linear.

Interestingly, in Resolve 19b4 Davinci YRGB Color Managed seems to provide better default color balanced transform to 709 of Alexa 35 than ACES cct. Anyone else had experience with Arriraw Alexa 35 material?

Yes, indeed.
I shot green and blue screen in ARRIRAW and debayered to LogC4.
I found by far best result to get when working in DWG to LogC4 Managed Colour space.
There was option with ACES as well as ARRI REVEAL option non colour managed LogC4 to LogC4 in DR 18.6
Green and blue screen were best keyed with DWG to LogC4 Colour Managed.

This may be Davinci thing but IMO you are right.
However, this does not changes anything as far as how you shoot.
Just film in Arriraw which is by default LogC4 or LogC3 in other Alexas.