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BMPCC 4K -- LUTs v. RCM?

PostPosted: Wed Oct 24, 2018 3:09 pm
by John Paines
The differences between the normalization which occurs with the BMPCC 4K log to video or extended video LUTs and RCM can be quite stark.

It might be helpful if somebody at BMD explained the differences, and the preferred workflow...?

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Wed Oct 24, 2018 7:21 pm
by rick.lang
Stark or shocking would describe what I found this morning on a shoot yesterday using the Mini 4.6K in firmware 4.8.

Normally I’m shooting CinemaDNG raw and when I bring the clips into Resolve (prior to using 15.1.2), they look very bad in the Media Page. But when I add the clips to the Media Pool with my ACEScct settings, they look decent and easy to grade.

Yesterday’s footage was shot ProRes 444 and looks quite good in the Media Page and shocking in the Media Pool when using ACEScct. All I did was switch to Resolve YRGB (15.1.2, not Colour Managed) and the clips in the Media Pool now look quite good before I do any grading.

I’m not sure what to conclude. My camera hasn’t changed, but ACES is now useless for me apparently with the only change possibly being the move to 15.1.2. Maybe I’ll find something wrong that I did. I can spend more time investigating later.



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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Wed Oct 24, 2018 7:28 pm
by John Paines
Sounds like you shot in rec. 709 rather than log. At least, what you describe is what would happen, if that's what you did.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Wed Oct 24, 2018 8:36 pm
by rick.lang
Thanks, John. Shot ProRes Film.


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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Wed Oct 24, 2018 9:35 pm
by Jim Giberti
John Paines wrote:The differences between the normalization which occurs with the BMPCC 4K log to video or extended video LUTs and RCM can be quite stark.
It might be helpful if somebody at BMD explained the differences, and the preferred workflow...?


It would be really good if they did.

I've been patiently waiting for that or for enough pro users to get their cameras to have an active discussion of work flow regarding everything to do with Gen 4 color science, Extended Video, BMPCC 4k luts...

It would be good for them to put together a white paper on it and/or get invloved here with the discussion.

FWIW and given our schedule and workflow, we've been shooting everything in ProRes HQ and bringing it directly into FCPX because it's the native codec and it's a no brainer for fast client turn around.

I've been experimenting with different ways to get the most out of the Film log ProRes footage that is very different from footage and therefore LUTs/workflow from our other BM cameras.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Wed Oct 24, 2018 11:13 pm
by Jamie LeJeune
rick.lang wrote:Thanks, John. Shot ProRes Film.

Are you sure you have the ACES IDT set correctly for all the clips?

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Wed Oct 24, 2018 11:38 pm
by Mike Manus
rick.lang wrote:Thanks, John. Shot ProRes Film.


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Did you try changing from auto to full levels in clip attributes?

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Fri Oct 26, 2018 1:38 pm
by rick.lang
Mime, I always specify full levels whenever the option is available.

Jamie, I thought I had done everything as I had done before Resolve 15.1.2. You know I’ve had very good success with ACEScct and use of Log primaries, for quite awhile now. I moved on to simple Resolve YRGB to grade the ProRes 444 video yesterday.

Thanks for the suggestions. Feeling a bit of a crunch due to other activities and just taking the path of least resistance this time.


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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sat Oct 27, 2018 8:22 pm
by Jamie LeJeune
Steps are different with cDNG v ProRes. It may have been setting the IDT automatically in raw, while in ProRes you’d need to set it manually on clips in Media Pool or set IDT project wide in Color Management

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sat Oct 27, 2018 10:40 pm
by CaptainHook
John Paines wrote:The differences between the normalization which occurs with the BMPCC 4K log to video or extended video LUTs and RCM can be quite stark.

It might be helpful if somebody at BMD explained the differences, and the preferred workflow...?

Can you show examples of the differences and explain your setup/workflow?
RCM is easy to get wrong and not have the right settings, but there's also a chance of an issue somewhere.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Oct 28, 2018 2:24 pm
by John Paines
CaptainHook wrote:Can you show examples of the differences and explain your setup/workflow?
RCM is easy to get wrong and not have the right settings, but there's also a chance of an issue somewhere.


Here's the log version, followed by log+P4k Film to Extended Video v4 LUT applied on the Color page, followed by the RCM version, with BM P4K Pocket Film selected as in the input colorspace in the Media Pool, and rec. 709 2.4 set as both timeline and output. Other settings on that page are left at the defaults.

It's understood that the RCM version isn't actually clipping, but the question is, where's the best place to start?

log.jpg
log.jpg (441.22 KiB) Viewed 3987 times


lut.jpg
lut.jpg (560.6 KiB) Viewed 3987 times


rcm.jpg
rcm.jpg (666.75 KiB) Viewed 3987 times

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Oct 28, 2018 7:49 pm
by CaptainHook
John Paines wrote:It's understood that the RCM version isn't actually clipping, but the question is, where's the best place to start?]

Oh, that's really a preference question and a case of finding what works best for you. Using RCM and 709 might require more work to pull the range back in how you'd like, but you may prefer the primaries and starting point. Alternatively you may prefer extended video and again you can adjust things pre/post LUT (or CST plugin) to taste.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Oct 28, 2018 8:04 pm
by John Paines
Well, the issue is the desire for highest accuracy -- the manual claims that RCM is better math. Is it?

I've stuck with RCM so far, generally preferring it, but have also worked on high contrast clips where the extended video v4 LUT solved problems instantly, that took a lot of pushing and pulling in RCM.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Tue Oct 30, 2018 4:10 am
by CaptainHook
John Paines wrote:Well, the issue is the desire for highest accuracy -- the manual claims that RCM is better math. Is it?

Its less about that, and more about a LUT needing interpolation for values in-between the defined lattice points and that it can/will clip data if it goes beyond the limits. Extended Video is fairly straight forward and should be totally fine at 33^3 with tetrahedral interpolation (change the default in Resolve project settings) so in this particular case I think you can choose the workflow that best suits how you want to work and not worry about which has more accuracy.

Hopefully Extended Video for the other cameras will come to RCM/CST in a future Resolve release soon so if you prefer RCM you will be able to stick with that.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Thu Nov 01, 2018 1:42 am
by Jamie LeJeune
CaptainHook wrote:Hopefully Extended Video for the other cameras will come to RCM/CST in a future Resolve release soon so if you prefer RCM you will be able to stick with that.


In theory it should be possible to get close with the tone mapping and saturation rolloff settings in RCM project level settings or by using those settings in CST nodes, right?

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Tue Jan 15, 2019 3:00 am
by David_Carr-Berry
Jamie -

re ACES workflow - you seem to have a handle on creating LUTS that do the input transform to ACES and the output transform to rec 709 displays. Can you talk through your process with Resolve?

And - are we dependent on Blackmagic creating input transforms for the new color sciences?

Thanks -

David

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Wed Jan 16, 2019 11:32 am
by Jamie LeJeune
Yes, ACES always requires an IDT defined by the camera manufacturer, so we are completely reliant on BMD for these from their cameras (same goes for Sony, Red, Panny, etc.), and the IDT has to correspond to the version of the color matrix the clips were recorded with. So, if you shot ProRes to BMD 4.6K Film v3, you need to use the IDT for BMD 4.6K Film v3, and if you recorded in the new v4, then you’ll need the v4 IDT, etc.

As for making LUTs that mimic ACES transforms to use for monitoring, just setup your intended input and output in Resolve and then profile it using the TrimLUT to create the LUT. You can find instructions for how to do that on page 118 of the most recent Resolve manual.

Also worth nothing is that, in my experience, ACES works best when fed raw source footage or lightly compressed 12bit 444 source files. So, I’d stick to BRAW or ProRes4444 if you’re planning to grade in ACES.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Wed Jan 16, 2019 11:14 pm
by rick.lang
I concur with Jamie’s recommendation, although there’s no ProRes 444 on the BMPCC4K. I’ll likely experiment shooting 4K ProRes 422 HQ and then in post transcoding to 2K ProRes 444 prior to grading. And compare that to shooting raw and BRAW Q0 when available.


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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Thu Jan 17, 2019 6:51 am
by Jamie LeJeune
rick.lang wrote:shooting 4K ProRes 422 HQ and then in post transcoding to 2K ProRes 444 prior to grading


Since Resolve pulls everything into 32bit float anyway, that transcode isn't going to yield any advantage in terms of bit depth or latitude for grading. If you plan to delete the original cameras files, it would, however, save you some drive space : )

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Thu Jan 17, 2019 6:33 pm
by rick.lang
Jamie, yes; since ProRes is compressed, you are probably right that 422 won’t yield 444 at half resolution. Makes more sense that I should shoot raw 3:1 4K and transcode that in post to ProRes 444 2K (for improved storage).


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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Thu Jan 17, 2019 11:14 pm
by Jamie LeJeune
Yep, that's your best bet until BRAW comes to the 4K Pocket :D

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Fri Jan 18, 2019 7:42 pm
by Rickiriva
Hello everyone, I'm having some troubles trying to grade the P4K ProRes Film files, I've set RCM to BMD Pocket 4k film the input color space and Rec.709 both timeline and output color space, but when I try to lower the lift setting the brighter parts of the image get even brighter. Is it supposed to work this way or am I missing something?


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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Fri Jan 18, 2019 10:24 pm
by rick.lang
Adjusting any lift, gamma, gain Colour Page primary does alter other areas. You just adjust one or more of the controls until you get what you want.


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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Fri Jan 18, 2019 11:09 pm
by John Paines
Rickiriva wrote:but when I try to lower the lift setting the brighter parts of the image get even brighter. Is it supposed to work this way or am I missing something?


There may be some issue here, with the primary wheel controls at times behaving in unexpected ways. It's not repeatable on demand, so it's hard to say what's going on.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sat Jan 19, 2019 6:55 am
by Rickiriva
rick.lang wrote:Adjusting any lift, gamma, gain Colour Page primary does alter other areas. You just adjust one or more of the controls until you get what you want.


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And this is to be expected if the other areas are dragged in the same direction of what you're trying to do, not the other way I think.


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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sat Jan 19, 2019 9:03 am
by Jamie LeJeune
Rickiriva wrote: when I try to lower the lift setting the brighter parts of the image get even brighter
When you drag lift down, are you actually seeing the absolute level of the highlights go up on the waveform? That would not be expected behavior.

If you lower lift, the brightest parts of the image should be mostly unaffected. By lowering lift, you are increasing contrast in the image, so relative to the shadows the highlights will appear brighter even though their absolute brightness hasn't gone up. I'd bet this is actually what you're seeing.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sat Jan 19, 2019 11:09 am
by Rickiriva
Jamie LeJeune wrote:
Rickiriva wrote: when I try to lower the lift setting the brighter parts of the image get even brighter
When you drag lift down, are you actually seeing the absolute level of the highlights go up on the waveform? That would not be expected behavior.

If you lower lift, the brightest parts of the image should be mostly unaffected. By lowering lift, you are increasing contrast in the image, so relative to the shadows the highlights will appear brighter even though their absolute brightness hasn't gone up. I'd bet this is actually what you're seeing.


No, it's the actual rgb parade that shows this weird behaviour, and that's why I was concerned about a possible incorrect setting in the RCM page.


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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sat Jan 19, 2019 2:41 pm
by John Paines
As noted above, there have been instances where the primary wheels behave as if they were actually different controls -- for example, the gain control behaves like the offset control. Or the lift control behaves like the contrast control, and you will indeed see highlights rising when it's lowered.

In my case, this occurred with certain clips, and not with others, also using RCM with BMPCC 4K clips. Hard to know what's going on, since it's unpredictable and usually not present.

BMPCC 4K -- LUTs v. RCM?

PostPosted: Sat Jan 19, 2019 6:12 pm
by rick.lang
I use ACEScct with log primary controls almost exclusively and notice some (unexpected) shift in the waveform that I use 100% of the time when grading. I never considered that a problem though as I’m using the controls to get an end result and I’m not presuming to know how it should work since BMD are the experts.


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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sat Jan 19, 2019 10:43 pm
by Jamie LeJeune
Rickiriva wrote:No, it's the actual rgb parade that shows this weird behaviour, and that's why I was concerned about a possible incorrect setting in the RCM page.
I tested a bunch of 4K Pocket clips in ACES and in RCM and can't replicate that behavior.
Can you post a video screen capture showing both the primary controls adjustment and the RGB parade so we can see the issue?

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Jan 20, 2019 2:27 pm
by Rickiriva
Jamie LeJeune wrote:
Rickiriva wrote:No, it's the actual rgb parade that shows this weird behaviour, and that's why I was concerned about a possible incorrect setting in the RCM page.
I tested a bunch of 4K Pocket clips in ACES and in RCM and can't replicate that behavior.
Can you post a video screen capture showing both the primary controls adjustment and the RGB parade so we can see the issue?


The only way I managed to share with you the video was by creating a Dropbox link to the file, hope it helps.

https://www.dropbox.com/s/j8j9ek7qp13ae ... 0.mov?dl=0

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Jan 20, 2019 2:38 pm
by John Paines
Yes, I've seen the same thing, though only on occasion. The lift wheel is behaving like a contrast control, raising and lowering levels at the same time.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Jan 20, 2019 2:41 pm
by Rickiriva
In my case this happens regularly, do you think this may be the case for a return of the unit?

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Jan 20, 2019 2:44 pm
by John Paines
You mean the camera? No, it's an apparent Resolve bug. Just out of curiosity, what happens if you leave every other value on the RCM page at the default (no saturation mapping, nits, etc.)? So you just set input space, timeline, output.

EDIT: if you can, link to a sample clip where you're seeing it.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Jan 20, 2019 3:02 pm
by Rickiriva
Sadly, no changes in controls behaviour.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Jan 20, 2019 3:03 pm
by Rickiriva
John Paines wrote:You mean the camera? No, it's an apparent Resolve bug. Just out of curiosity, what happens if you leave every other value on the RCM page at the default (no saturation mapping, nits, etc.)? So you just set input space, timeline, output.

EDIT: if you can, link to a sample clip where you're seeing it.


The previous post has a link attached to a screen recording where it's noticeable.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Jan 20, 2019 3:05 pm
by John Paines
I mean provide an actual camera clip from the BMPCC 4K to download, where you're seeing this behavior.

The other thing you could try is to turn off RCM and use a LUT (if you want) instead. And see if the same thing happens.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Jan 20, 2019 3:31 pm
by Rickiriva
John Paines wrote:I mean provide an actual camera clip from the BMPCC 4K to download, where you're seeing this behavior.

The other thing you could try is to turn off RCM and use a LUT (if you want) instead. And see if the same thing happens.


Oh sorry, I didn't understand your request properly, here's a link with a clip straight out of the camera. It's a bit overexposed and I found out that this strange thing occurs after a bit of pushing and pulling, trying to have a satisfying image.
https://www.dropbox.com/s/lz044pxb32b8t ... 7.mov?dl=0

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Jan 20, 2019 4:03 pm
by John Paines
I'm seeing the behavior you've noted, on this clip, though how obvious it becomes depends on prior adjustments. You'll also note that if you use the gain control, everything will move -- it's functioning like the offset wheel.

I don't know what's going on. It's always possible there's a user-error explanation, but I don't see it.

In the meantime, if you want to avoid this issue, use Resolve YRGB instead, with LUTS. It's not occurring there.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sun Jan 20, 2019 4:10 pm
by Rickiriva
Ok thanks, I didn't really want to use LUTs but maybe it's the only thing to do at the moment. Thank you!!

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Mon Jan 21, 2019 6:32 pm
by John Paines
On certain clips, I'm seeing the same odd behavior with LUTs as well. Am not sure what's going on here.

BMPCC 4K -- LUTs v. RCM?

PostPosted: Mon Jan 21, 2019 8:31 pm
by rick.lang
Funny I have been busy grading videos and haven’t seen the phenomenon happen, but I’m sure it has in the past!

I’m on the latest Resolve 15.2.2.

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Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Mon Jan 21, 2019 8:44 pm
by Rickiriva
John Paines wrote:On certain clips, I'm seeing the same odd behavior with LUTs as well. Am not sure what's going on here.

Yes, I'm seeing the same thing, it's driving me crazy.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Thu Jan 31, 2019 6:00 pm
by John Paines
Rickiriva wrote:Yes, I'm seeing the same thing, it's driving me crazy.


It appears to occur on clips where there's a large reduction in the offset values -- typically over-exposed material, where you'd go into single digits or negative numbers.

When the footage has to be brought way down, use the primary wheel lift control instead for the first adjustment.

Re: BMPCC 4K -- LUTs v. RCM?

PostPosted: Sat Feb 09, 2019 5:32 pm
by Rickiriva
Thank you!!


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