Raw DNG from BMCC to BLD Film to VFX and back

Hello,

I'm new at this, so please excuse me for occasionally saying the odd dumb thing. I've searched the forum and read the similar posts, but I haven't figured it out completely in my case.

We've shot something with the BMCC as raw. On the Camera RAW settings in Resolve, I'm outputting in BMD Film colour and gamma. For shots with no vfx, I either put a BMDFilm -> rec.709 LUT at the very end of the chain (usually the timeline grade), or create a proper grade from scratch. This is all well and nice.

The problem is that there exists a substantial number of shots that must go to Fusion (the free version, if that matters), After Effects, and as a helper guide to 3DS max. The latter we usually get from the proxies as rec709 and let 3DS linearize it along with the textures. It's the compositing apps that get me confused. Obviously we need the proper footage, I understand the best way would be image sequences (say, half-float EXRs). But I also need the result to be in the same space as the other shots to grade them together, so I'll need it in BMD Film. Unless that's wrong or impossible...

So, I can add an export LUT in Resolve (BMD Film -> Linear) to write out the EXR. However, in, say After Effects, while I know we can change the display gamma, how do we get a BMD Film -> rec709 colour conversion on the viewer to be able to work properly? Can I somehow use Resolve's LUT for this?

If I instead linearize the shots after I convert them to rec709 in Resolve, then I'd need to convert it back to BMD Film when I import back the composited shots (to bring it in the same state with the others), but that sounds like a recipe for clipping and assorted conversion degradations to me.

Is my idea of this workflow flawed somehow? What would you recommend? Btw, as you've figured out, we're all just starting out, so my cg guy (girl, actually) can't really help either, but is looking forward to learning this workflow.

Thanks a lot!
Dani

Ok, I know most of you guys are busy with v12 right now, so this is a sort of bump, at the same time sharing with you where my experiments have led in the meantime:

I was able to get what seems like a good roundtrip by exporting the raw, ungraded camera footage from Resolve (with only the camera raw settings adjusted to be suitable), via the BMDFilm -> Linear LUT, in half-float exr, then the files that get returned to me from AfterEffects look essentially identical through the reverse LUT, and I can apply pretty much the same grade to these shots along with the others (that didn't make the roundtrip).

What I'm trying to do now is export a LUT with the rough grading info, so that the VFX artist can see how the shot will be graded and manage her work accordingly. Simply exporting the current grade as a LUT won't do, as that grade is meant for a BMD film input space, whereas the footage in AE is linear. Would adding a Film->Linear LUT node before the grade, then exporting the whole thing as a LUT, work? Again, I want the VFX artist to work with linearised media as they came from the camera, and see in her display the rough grade that I made as a reference, to have a proper feel of the shot, without of course exporting it. The feedback I got this morning from her was positive (she had to remove the "add 2.2 gamma" compensation in AE's preferences for linear media, as that was already in the LUT, but she says the picture looks very similar to what it did before export).

Does that make sense, or am I overcomplicating things?
Sorry for posting again, I hope you guys can point me to the right direction.

Have your VFX artist read this book:

The VES Handbook of Visual Effects: Industry Standard VFX Practices and Procedures
by Susan Zwerman & Jeffrey A. Okun
published by Focal Press [ISBN #0240825187]
http://www.amazon.com/VES-Handbook-Visu ... 963&sr=1-1

The book details several workable VFX workflows that can function perfectly well. One is to have the project colorist color-time the VFX background plates to get them at least 2/3 of the way there, then use a very mild 3D LUT to approximate a Rec709 look. Another way to do it is to manually correct the BMDFilm footage to an acceptable image in Rec 709 space, then export that look as a 3D LUT. Apply that LUT as a viewing LUT in the top layer of the VFX process, then turn it off when the VFX are rendered. I've used both methods on different projects and each can work. The key is that the VFX people provide material that can still drop into a color-timed sequence and match all the non-VFX shots around it.

EXR may be overkill for your material if you're struggling with time and budget. If you do have time and budget, then I'd suggest you hire a post-production supervisor and/or a VFX supervisor, both of which will save you much time and money.

Thank you Marc for your reply and book recommendation.

We have essentially zero budget, but we do have relatively plenty of time. We're not a post studio, just a self-funded non-profit, we do stuff for ourselves, not clients. I wish we could get a supervisor, but that's impossible (both in terms of budget, and also because I don't think one exists in Thessaloniki, Greece, where we are based).

Your concerns over exr relate to rendering time? Disk space? Something else? Do you recommend another container? I suspect we could use something like ProRes4444, but we figured if we're learning this, we might as well get into the linear workflow thing, and EXRs would make the 3D multi pass stuff more manageable by bundling all the passes, so we figured we'd use it throughout. Also, I'm normally an audio engineer and I've come to love floating point math throughout the years, I understand that the benefits in images are largely similar.

We have tried the approaches you mentioned, and have settled with your second option. It's the linearisation that's causing the problem (we output the vfx plates with a BMDfilm->Linear LUT, so that we can implement a linear compositing workflow). Since the grade in Resolve is a correction that brings the BMDfilm footage to look like it is in rec709 space, it doesn't work for linear images (wrong input space, particularly the gamma).

So my not very clean solution was to combine this grade with a Linear->BMD Film LUT before it, and export that (combined) for the VFX artist to monitor through. Not very pretty, but we did a roundtrip of an unaltered plate and it came back essentially identical, while the VFX artist said the images looked fine through the supplied LUT.

Anyway, thanks again for your help.

I think there are simpler methods that might work faster and more effectively for you. Bear in mind there are TV shows that are routinely produced at a feverish pace, with VFX budgets not nearly as high as you might expect. It's not unusual for 3-4 day turnarounds on some shots in many cases, all using a fairly straightforward workflow with standard files. EXR may be complete overkill for what you're trying to do, and we're talking 4-5 times larger file sizes (with corresponding delays in copying, backups, and changes).

I don't quite understand the fear which is mongered towards exr workflows and also what you are comparing it to when talking about 4-5 larger file sizes.

Within the vfx workflow (not on its ends) the only reasonable filetypes are dpx and exr. Every other is not acceptable in the long run, for varying reasons. Working with not frame based container formats is a no-no. The very few advantages it has gets outweighed rapidly with every bit of complexity you add to your vfx work. So it's a bad idea to begin with, because you never know how much complexity will be added along your way.

The main difference between exr and dpx in the workaday life is that dpx will be written and read faster then exrs. The filesize is about the same, depending on the contents of the image. exr has the advantage that you can throw anything at it as far as values and channels are concerned. As you will render exrs out of your 3d package it might make sense to stick with it all the time to keep it consistent. On the contrary, it might make sense to use dpx in compositing because you can use it directly in Resolve, which is depending on your machine not the case with exr.

That all being said, I don't see what your specific problem is. Write linear exrs, either by turning the gamma to linear in the camera raw settings or by lut. Keep in mind that when using a lut, you might loose high values because Resolve clips them. Bring it into and out of your composting package without any color transformations (which should be done by default when using exr) and bring it back into resolve. Now you have exactly the same colors as before and you can use a LUT to bring it to the colorspace you want to do the grading in.

we have essentially zero budget, but we do have relatively plenty of time. We're not a post studio, just a self-funded non-profit, we do stuff for ourselves, not clients. I wish we could get a supervisor, but that's impossible (both in terms of budget, and also because I don't think one exists in Thessaloniki, Greece, where we are based).

more reason to get the book and learn the ropes: once you get it right you will never forget.

I just bought the Nuke 101 (v8) book even if I need nuke only on a sporadic bases....

Thanks everyone for the responses.

I've ordered the book, looking forward to it.
In the meantime, the linear exr solution seems to be working very well (we're shooting at 2.5k, and our machines and drives seem to be able to handle the bandwidth in realtime). It just took some work to figure out the correct LUTs for the vfx artist to monitor through (that include our preliminary grade as a design aid). We carefully monitor the material to avoid clipping. Granted, we could use substantially smaller files for the simpler stuff (replacements etc), but like Til said, the 3D stuff will be exr anyway, and we were more after exploring possibilities than producing content quickly this time.

That said, next time I can think of so many things I'd do different...
Great forum, thanks again.

Thanks everyone for the responses.

I've ordered the book, looking forward to it.
In the meantime, the linear exr solution seems to be working very well (we're shooting at 2.5k, and our machines and drives seem to be able to handle the bandwidth in realtime). It just took some work to figure out the correct LUTs for the vfx artist to monitor through (that include our preliminary grade as a design aid). We carefully monitor the material to avoid clipping. Granted, we could use substantially smaller files for the simpler stuff (replacements etc), but like Til said, the 3D stuff will be exr anyway, and we were more after exploring possibilities than producing content quickly this time.

That said, next time I can think of so many things I'd do different...
Great forum, thanks again.

hey Dani,
I usually do a final grade, then save a still of that grade, after which I save a 3d Lut of the grade and export it to my Lut folder, or on my desktop. I then disable all grades, except the raw camera settings In Resolve. I export the footage via EXR. ( The footage of course looks ungraded like bmd film) I'm not familiar with Fusion yet since i'm on a mac, so i'm stuck with with after effects to composite. OK now i import the EXR footage into after effects.. put the EXR footage into a comp then add red giant's Lut buddy or lut utility on the footage. I Import the Lut via those Lut utilities..after adding the lut, my footage look just like it did in Resolve ( just remember to click the Preserve RGB box in the color management tab under project settings) After i add my 3d models or explosions vfx.. i use the primette keyer effect..onto the comp or solid of the 3d models /explosion or whatever i'm trying to blend into the scene. In primette keyer scroll down and you'll see "background layer"..in that tab select your EXR footage..then under that click enable color match. Its set to 50% but you could play with those setting to your desire..to help match the vfx to your scene. After that i also add the same lut i put on my EXR footage to the vfx using the Lut utilities ..depending on your Lut it may be dark or lite or maybe just right.. like the three little bears and their porridge If its to dark or lite for your taste, you can add a curves adjustment to brighten it or darken it to your desire. After getting the look you want with other tools you may use along with what i mentioned here, you can export the footage Via EXR.. go back into the projects settings tab and uncheck Preserve RGB.. Now Your footage will look washed out again along with your Vfx.. This box is also where you can add whatever color space you want, i use SRGB. After you Export. Import it into Davinci resolve in your original grade session and then finally back into the color page.. drop your still of the grade you saved on top of the footage..and it should/will look like what it looked like in after effects. I know thats my crazy Process but it works for me.. By the way i'm using a mid 2011 iMac with graphics card not rated for most things that i do..but i have no problems with .EXR files it all render fine and fast.. below is the primette keyer tab..and below that is a screen shot using the process i mentioned above adding the helicopter in the scene. I used a bmp4k for the back plate. Of course if if anyone else has another way i would love to try it as well.

Primette keyer Tab.png (275.41 KiB) Viewed 8423 times

This is a still shot of my process adding that 3d model in the scene.png (826.83 KiB) Viewed 8423 times

Hi Donnell,

Thanks for your answer. We do largely the same thing, but we linearize the images first (really important if you composite multi pass 3D, but I'm given to understand is a good idea in many cases where there's a lot of blending involved). So in Resolve, after disabling whatever grade I had, I add a BMDfilm to Linear LUT, making sure I'm not clipping anything. I'm not sure how the VFX person handles this in After Effects, I think she enables the "linear working space" setting or something, but not the "output 2.2 gamma" checkbox. For the LUT, I have a gray band generator in Resolve in a different timeline, and I first add a node with the ""Linear to BMDfilm" LUT, then my original grade (that was meant with BMDfilm as the input space). That LUT gets used in After Effects for display. My problem was figuring out that if I just exported the grade, then After Effects applied the corrections in the wrong order (i.e., LUT first, then gamma, which was in the preferences), which of course doesn't work. By bundling the grade with the delinearize LUT in the correct order, we fixed that. So, in Resolve, the returned exrs get converted to BMDfilm as a first step, and then have the same original grade applied to them. As a test, we tried a roundtrip with an unaltered image and blended it with the original in subtract mode, and we got black, so it must be mathematically correct, I think.

Just a few notes I want to add to this:

The colorspace in which your images are stored doesn't affect the colorspace your are working in. You can have non-linear exrs and linearize them when they come into your compositing package. The only reason you shouldn't produce non-linear exrs is, that it contradicts the whole idea behind the format, which is that it always contains linear light image data and saves you from the hassle of gamma and colorspaces.

Additionally you can also have it the other way around, that you read linear exrs but delinearize them on input which is exactly what AFX does by default. Because it stores it back to linear on export, you wouldn't notice this fact as long as you don't specifically look for it. I don't know how things have changed, for I stopped using AFX actively somewhere around CS5/CS6 but it would make it quite hard to work in linear back then. It was (or is) only possible by choosing a colorspace based on an icc-profile what a lot of people would you recommend not to do because it leads to color inaccuracies.

On this whole why-do-vfx-in-linear-light thing, which is rather theory than specifically workflow related, I would recommend reading Stu Maschwitz's blog ( prolost.com ) on this matter. Have a look for the "image nerdery" tagged posts going back from 2009.

And again: if you use a LUT in Resolve to export exrs, it will clip at a value of 1 (white). Only if you don't have values in that area, the clipping doesn't concern you.

Yes you are right ..I linearize as well in after effects.. Funny i actually wrote that part in the previous post but then deleted it, as I was trying to keep it as simple as possible. ..as for dani since your workflow is similar to mine ..you shouldn't have to much of a problem on your hands..

you read linear exrs but delinearize them on input which is exactly what AFX does by default.

I'm not sure which version we're using, but I know that there's a checkbox that says "add 2.2 gamma" or something like that, which is supposed to affect the display only. We don't use that, so without the LUT it's obvious by eye that the data is actually linear (also because the LUT works perfectly). Since this is the raw camera footage, we just make sure that the data does not clip in Resolve (incl. using the highlight recovery function and adjusting gain if necessary). Any additional exposure that might cause data to clip intentionally is done on the grade, which is monitor only. Come to think of it, procedurally linearising the data would be better, but I think I'll leave that for the next project.