Alexa 35 Anamorphic Editing

I'm working with the Alexa 35 on a feature that is being edited in Davinci Resolve and I'm getting some unexpected results that I'm hoping you all may have some insight into.

I'm in Resolve 18.6 on an M1 Macbook Pro running Sonoma 14.2.1 and on the Alexa we're shooting Open Gate 4.6k with a 2x anamorphic desqueeze. When loading the footage into Resolve the 2x desqueeze is handled properly and the footage looks great. My understanding is the anamorphic file should retain it's vertical resolution of 3164 but double the horizontal resolution. However when I load the footage in a timeline with a square pixel ratio of 9216x3164 the file is half the size.

When I load the same footage into Premiere with a 9216x3164 sequence it fills the frame. Anyone have any ideas of what might be the issue in Resolve?

Thanks

It's anamorphic so the pixels are no longer 'square' would be my guess. If you can supply a frame grab or clip, I could have a look.

However when I load the footage in a timeline with a square pixel ratio of 9216x3164 the file is half the size.

Crazy question: why are you working in 9K? Uprezzing the material will not yield any picture quality improvements (at least to me) -- I don't see this as a good workflow at all.

Scope deliverables are 4096x1716 (theatrical) or 3840x1607 (streaming/home video), and those are legitimate aspect ratios. To me, doubling these numbers would simply make the system work twice as hard with no actual improvement in picture quality.

Worst case: call Arri and ask to speak to a workflow specialist. They can give you real-world advice compatible with whatever systems you're using:

Arri Americas
3700 Vanowen Street
Burbank, CA 91505
(818) 841-7070

Crazy question: why are you working in 9K? Uprezzing the material will not yield any picture quality improvements (at least to me) -- I don't see this as a good workflow at all.

Yes exactly Marc, and then trying to fit a square pixel, that now has an aspect ratio. into a wide 'round' hole; as I say my guess> 4K DCI project; non-square Aspect ratio 2:1; would be what I'd try, Andrew.

BTW saw you in that video with the very nice Darren Moyston; very cool sir!

Thanks for the replies guys. I understand the issues with the anamorphic de-squeeze. I'm not concerned about the horizontal resolution. My only concern is that Resolve is showing half the vertical resolution of 1582 instead of the 3164 that it's originally shot in. This may become even slightly more of an issue because we're cropping in slightly due to the lens not quite covering the open gate sensor so I don't want to lose even more vertical resolution.

In my mind the footage in Resolve should show the same resolution as in Premiere/Finder/Arri software of 4608x3164 (2.0) Not 4608x1582(2.0) as it's showing in Resolve.

Can you post a short sample to a cloud service to look at?
I have used Red anamorphic stuff in the past and it scaled correctly.

Yes absolutely, sorry for the delayed response.

I've a shot here that's downloadable for reference: https://spaces.hightail.com/receive/pbloX7ibqw

I also took some screen grabs of the footage and sequence in bins to show the resolution:

1582 timeline https://drive.google.com/open?id=13b3wp ... p=drive_fs]
1582 clip. https://drive.google.com/open?id=13eD7L ... p=drive_fs
3164 timeline. https://drive.google.com/open?id=13fi8_ ... p=drive_fs
3164 clip. https://drive.google.com/open?id=13jQ_x ... p=drive_fs

Sorry couldn't get the image embed to work.

You are right, there's a minor issue, if you insist on such high resolution, but a workaround too. While your footage is correctly identified with a 2.0 PAR, it's only shown correctly in a DCI Scope timeline. If that doesn't show on your side, it might be a Sonoma issue. I'm trying to avoid that OS as long as I can!

If you insist, you can set your intended resolution in 9216x3164 as Custom and tell DR to use Stretch for scaling (Stretch frame to all corners). I'd be curious to know, though, how a humble MBP is handling that on render

If the automatic scaling doesn't work for you (it does for me under Ventura), you can use the same setting to fill a regular DCI size Scope timeline, as already given by Marc. Or make an unconventional timeline of 4608x1582 as custom to preserve every horizontal pixel. But I'd rather first ask about the expected delivery.

Thanks for taking a look Uli. I also wanted to wait on Sonoma but I was forced onto it due to a Shotput update.

The scale up does work but in my mind there shouldn't be a reason to scale up, and are we going to lose some quality with that process? We honestly don't need much more than the 1/2 resolution version anyways but I would prefer not to have to scale at all. Our final output will be slightly shorter than 4k Scope as we're going with a 2.5:1 aspect ratio for a resolution of 4096x1638. Or more likely still at regular DCI scope with bars, but the image would actually be 1638 high. With our current height of 1582 we would only have to scale up slightly but due to the vignetting of the lenses we will lose a smidge more vertical resolution.

I do realize this is mostly just pixel peeping and won't make a huge difference in the end but my concern is really just with how Resolve is handling the files and why it's needing to be scaled up, and why the vertical resolution isn't showing the way it should.


Although the MBP won't be the edit system I did do a little test render just to see. The original resolution render at 4608x1584 to 1:54 while the 9216x3164 took 5:13. So certainly a significant bump.

The scale up does work but in my mind there shouldn't be a reason to scale up, and are we going to lose some quality with that process?

Well, if you shoot square photo sites open gate for CS, you have to scale, whatever you do. At least you'll downsample massively in the vertical dimension, and without reframing even a bit in the horizontal, going from 4608 to 4096. Who says you are upscaling? BTW, DR offers several algorithms for scaling, some smoother, some sharper. Your choice.

The only important point is setting the right size of your timeline before rendering. DR will use whatever source information you have, and it'll even warn you if you forget to change the setting.

Please learn DR thoroughly before tackling a big project for cinema.

Young Padawan.jpeg (12.89 KiB) Viewed 557 times

I don't think the condescension is required, or particularly warranted. I never claimed to be an expert in Resolve but I am familiar with the scaling options and how to output properly formatted sequences.

Perhaps I haven't been clear enough but I've only been asking one question that no one has attempted to answer yet: While Resolve sees the vertical resolution in the bin correctly at 3164, why does it not fill a timeline with the resolution set to 3164? Why does it come in at half the vertical resolution of the clip? If it's just something Resolve is doing under the hood and it's actually using all the pixels but showing only half in the metadata that's fine, I'm just trying to understand what's happening. Did this not happen on your system when you loaded the files?

Again: have you contacted Arri? They're nice people and will answer questions. I believe they even have tech papers that go over the workflow in great detail. Tons and tons of real-world workflows and ideas and setups:

Alexa 35 Workflow
https://www.arri.com/en/learn-help/lear ... -workflows

Perhaps I haven't been clear enough but I've only been asking one question that no one has attempted to answer yet: While Resolve sees the vertical resolution in the bin correctly at 3164, why does it not fill a timeline with the resolution set to 3164? Why does it come in at half the vertical resolution of the clip? If it's just something Resolve is doing under the hood and it's actually using all the pixels but showing only half in the metadata that's fine, I'm just trying to understand what's happening. Did this not happen on your system when you loaded the files?

That doesn't happen here.
It is coming in at full height, but even if the Metadata are correctly indicating a PAR of 2:1, it is not getting unsqueezed horizontally if the timeline is set to your custom size.
That's not to say that everything else is in order, for example 18.6.6 doesn't trim files from the new Alexa correctly in Media Management.

Sorry if I came across to 'teacherly', but I was under the impression that you are involved in post for the project, and your repeated question about resolution on Deliver seemed a bit uninformed.

P.S. Works as expected under Ventura in 19b2 in a DCI timeline for CS.