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DAVINCI RESOLVE ALEXA NODE WORKFLOW let me know if correct

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Daniel Williams
DAVINCI RESOLVE ALEXA NODE WORKFLOW let me know if correct
on Aug 7, 2016 at 5:22:52 am

heres my Alexa workflow, new to davinci, but proficient. Let me know if this makes sense, in order to maximize fidelity and Dynamic range!

1. You have a first node which is just your Log image.

2. Then your next serial node is your rec 709 conversion (arris LUT). This node is the one that obviously converts the image to linear and also, brings the colors into legal range and saturation (important).. You can reduce the opacity of this LUT if you want a lower contrast image. I choose 80%.

3. subsequent nodes are localized exposure control, power windows, ect.

4. The very last node far right in the tree is your creative look/output node. The final node all this happening under. Could be as simple as a creative 709 lut you found at varying opacity. Teal shadows. Overall Warmth .. Whatever. You would also add a vignette to this final output node.

With the first node selected, You correct the log UNDERNEATH the 709 (second node) using the Log wheels and Offset, to make the 709 image balanced on the waveform. This way you preserve dynamic range, instead of converting to 709 then trying to bring highlights back ect.

Usually, you want to go through your entire time line with just the first two nodes to get each and every shot balanced for exposure using the base 709 as your output reference and viewing on scopes. So they all match.

That way you can easily slap a last creative node on the whole thing and bam.

Does this make sense??


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Marc Wielage
Re: DAVINCI RESOLVE ALEXA NODE WORKFLOW let me know if correct
on Aug 8, 2016 at 9:55:18 am

There are lots of different ways to do it. With camera originals, I usually try a "normalizing" node to get a ballpark adjustment. From Alexa ProRes, that would be Log-C. Subsequent nodes change color, level, add windows, keys, and whatever additional looks the client wants. There is no "best" method, and a lot boils down to the circumstances in which you need to work (particularly time & budget).

I don't think a LUT is necessary, but some disagree and they can work. The Arri LUT generator on their own website is very flexible and does a reasonable job. But you can duplicate the processing of a Log-C -> Rec709 LUT just with the curves and primaries within Resolve. Pay close attention to saturation as well, particularly the Hue vs. Sat curve.


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Daniel Williams
Re: DAVINCI RESOLVE ALEXA NODE WORKFLOW let me know if correct
on Aug 8, 2016 at 7:10:12 pm

I understand there are 3473285943285 ways to skin a cat in resolve, but the order of operations, node order, and the method of going about something, do truly matter, in my testing least!

For instance, I treat the 709 conversion node as a standardized non-changing layer, and manipulating the Log footage in node before it, produces consistent results. Because the 709 LUT is engineered by Arri to expect a healthy exposure at 800, I can manipulate the Log with the log wheels to make sure the levels are in the right place before being transformed by the LUT

This is much better and results in greater fidelity than, say, converting to 709 and using the primary wheels to play with the image once its already clipped!


And Yes i am aware a LUT isn't entirely necessary as a starting point, but in my experience, Arris 709 LUT was designed with years of research and care in mind and makes the most of the sensor data in a more perceptually linear space. I feel the results are much more accurate and careful, than just blasting a LOG gamma shot with curves...

Also, it is a 3d LUT so you get saturation and hue in the proper legal ranges. impossible with just curves and saturation. Or am i wrong? (probably!)

Thoughts? What is YOUR procedure with balancing and correcting exposure for Log gamma shots?


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Marc Wielage
Re: DAVINCI RESOLVE ALEXA NODE WORKFLOW let me know if correct
on Aug 9, 2016 at 12:32:47 am

Somehow, my method has worked for me for a few hundred features and shows over the last few years. Maybe I've been lucky.


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Daniel Williams
Re: DAVINCI RESOLVE ALEXA NODE WORKFLOW let me know if correct
on Aug 11, 2016 at 4:10:14 am

What is your process/order exactly?

Is it true that you can get Rec709 legal colors from log by just adding contrast and saturation?

________________________
Freelance cinematographer/colorist
Alexa Mini Owner


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Marc Wielage
Re: DAVINCI RESOLVE ALEXA NODE WORKFLOW let me know if correct
on Aug 12, 2016 at 12:54:46 am

[Daniel Williams] "What is your process/order exactly? Is it true that you can get Rec709 legal colors from log by just adding contrast and saturation?"
It helps to shoot a color chart (like the DSC or the XRite Color Checker Video) under controllable conditions. Once you have that, you'll figure out what kind of gamma curve, chroma settings, and chroma/hue settings are needed to get accurate results. From there, you just dial in the look and move on.

You can also use the factory Rec709 LUT and compare that to your own correction. It's possible to just eyeball the picture and scopes and match it that way, but easier with a chart.


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Daniel Williams
Re: DAVINCI RESOLVE ALEXA NODE WORKFLOW let me know if correct
on Aug 13, 2016 at 4:38:44 am

I understand that, but I was under the impression you can never get the same results from manipulating the Log from scratch, that you can with a 3d LUT that converts RGB values into other RGB values and makes them 709 legal


Please someone explain this to me?

________________________
Freelance cinematographer/colorist
Alexa Mini Owner


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Marc Wielage
Re: DAVINCI RESOLVE ALEXA NODE WORKFLOW let me know if correct
on Aug 13, 2016 at 6:31:24 am

[Daniel Williams] "I understand that, but I was under the impression you can never get the same results from manipulating the Log from scratch, that you can with a 3d LUT that converts RGB values into other RGB values and makes them 709 legal"
Yes you can. You just have to work at it. There is nothing magical about a 3D LUT, particularly one as simple as the Arri Rec709 LUT. All it takes is time and effort.


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