Author Topic: Slightly darker image after importing into Resolve  (Read 1231 times)

zz77yy

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Slightly darker image after importing into Resolve
« on: November 08, 2017, 07:50:12 AM »
Hi, hoping to get some advice here. Been trying to work this out for about 3 weeks, but have not been able to find the correct info, so my apologies if this has been posted already but I can't find it.

I'm shooting raw on 5DmkIII, Latest Build 1.2.3 (2017-10-31 01:12) -but also happens on any other previous build, so its not the build I'm sure.

I convert my files to DNG with Switch and don't change any settings.

The DNG files I get out of Switch look PERFECT, they are exposed how I exposed them in-camera and all seems good.

The problem is when I import the DNG's into Resolve, they are always a fair bit darker than the DNG's.

I'm using Resolve 14.

I've tried a million different combinations of the Timeline colour space settings in the project settings, and nothing seems to make any difference to the overall exposure when I import them. The different Timeline colour space settings mainly seem to effect colour/saturation, and not so much exposure.

It doesn't seem to matter if I use the Decode using clip option and change the colour space and gamma settings there either, it gives me a slight improvement but it seems the damage is already done, ie. the files are already darker than they are supposed to be.

I have then been pushing them up using exposure and shadows sliders in the camera raw settings on each clip to get them back to proper exposure, but I find this is introducing a lot of noise.

All I basically want to do is get my DNG's into Resolve how they look in Finder when I preview them before going into Resolve.

The brighter image below is screen grab from Finder, the darker image is a screen grab from Resolve.

Also I've tested opening the DNG's in Adobe Camera Raw and they look fine in there.

The main reason I want to go to Resolve is to export ProRes so I can then edit in FCPX.

Any help or ideas would be much appreciated.







 

Levas

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Re: Slightly darker image after importing into Resolve
« Reply #1 on: November 08, 2017, 01:37:13 PM »
What bitrate are you using, 10, 12 or 14 ?
I'm not sure, but I have the idea that some programs don't read/display the lower bitrates right, lower bitrates are displayed darker.
But that should be fixable with exposure compensation in post process, are you sure you're getting much more noise when compensating ?

Danne

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Re: Slightly darker image after importing into Resolve
« Reply #2 on: November 08, 2017, 01:55:01 PM »
Could be white/black level related. Upload a sample MLV or dng.

bpv5P

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Re: Slightly darker image after importing into Resolve
« Reply #3 on: November 08, 2017, 02:06:46 PM »
What bitrate are you using, 10, 12 or 14 ?

bitrate != bitdepth


Check the default gamma and black level, as @Danne said. If nothing works, do some testing:
1- Save your configuration profile from Resolve.
2- Uninstall it and remove all folders/configuration files.
3- Flash latest compilation of ML nightly builds.
4- Record a small footage on all bit depth possible
5- Reinstall Resolve (do not load your configuration profile)
6- Open each of the test footages

All of them are dark? If all are dark, then it's probably not a issue with Resolve. If no one can reproduce it on Resolve, then the issue is on primary conversion (in your case, Swift). In the last case, you should talk with the developer...

Andy600

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Re: Slightly darker image after importing into Resolve
« Reply #4 on: November 08, 2017, 03:28:28 PM »
Adobe Camera Raw and any app that uses the Adobe DNG SDK will usually render DNGs with a tone curve. The tone curve has the effect of increasing exposure by approximately 1 stop and adds contrast but the actual curve applied is more than just simple gain and is camera-specific.

Resolve's DNG engine (Libraw) does not add a tone curve so what you see in Resolve is just the result of the output transform (Rec709, sRGB etc) and will typically appear darker compared to ACR, Finder etc. Try setting Resolve to YRGB and the raw panel to Rec709 then add ~1 stop of exposure in Resolve.

Increasing raw exposure in Resolve does not increase noise but you may see it more in Resolve compared to ACR which adds some noise reduction by default.
Colorist working with Davinci Resolve, Baselight, Nuke, After Effects & Premier Pro. Occasional Sunday afternoon DOP. Developer of Cinelog-C Colorspace Management and LUTs - www.cinelogdcp.com

Kharak

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Re: Slightly darker image after importing into Resolve
« Reply #5 on: November 08, 2017, 05:05:27 PM »
What worked best for me when i imported DNG's straight in to resolve was to set colour space to Log-C, all of them timeline, input, output. Increase exposure in camera raw tab by atleast 1+ usually more. That gives the closest to ACR output, exposure wise. I also think the log-c colour space correlates best with the 14 bit files for CC/CG.


once you go raw you never go back

Danne

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Re: Slightly darker image after importing into Resolve
« Reply #6 on: November 08, 2017, 09:54:03 PM »
Thanks for the info. Had no idea libraw was used in resolve.

bpv5P

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Re: Slightly darker image after importing into Resolve
« Reply #7 on: November 08, 2017, 10:34:32 PM »
Is it true, though? I couldn't find any confirmation about this.
Also, all software using dcraw automatically apply this curve, Andry600?

Andy600

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Re: Slightly darker image after importing into Resolve
« Reply #8 on: November 08, 2017, 11:03:53 PM »
Is what true?  ???

The curve? Yes. Look through the DNG SDK. Technically this tone mapping curve is a 'look' designed for print media and is not applicable to video but we are so used to how Adobe's ACR, Photoshop and Lightroom render raw images that we assume it to be correct.

ARRI, Canon, Sony, Blackmagic etc  all have their own version of tone mapping (think the various manufacturers 'Rec.709' looks, non of which match) and the DNG curve is simply another tone mapping but relative to a specific camera. It's neither right nor wrong.

Any tonemapping you apply (lut, curve, LGG, CDL etc) can live under the display transform either to produce a 'look' or something more scientific such as matching defined AIM values of a color chart.

Resolve using Libraw? Yes. look in the Resolve program folder and run process monitor to see the dll being called. Libraw can be compiled to include the DNG SDK but Resolve's libraw.dll is too small for that. It also seems to use Libraw for Canon .cr2 which is a bit odd because Canon also has an SDK but that might be due to implementation/GPU acceleration issues.
Colorist working with Davinci Resolve, Baselight, Nuke, After Effects & Premier Pro. Occasional Sunday afternoon DOP. Developer of Cinelog-C Colorspace Management and LUTs - www.cinelogdcp.com

bpv5P

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Re: Slightly darker image after importing into Resolve
« Reply #9 on: November 08, 2017, 11:27:50 PM »
Nice, thanks :^)

Andy600

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Re: Slightly darker image after importing into Resolve
« Reply #10 on: November 09, 2017, 12:25:14 AM »
The default forward and reverse tone curve operator (math and lookup tables) can be found in dng_render.cpp (in the SDK).

Colorist working with Davinci Resolve, Baselight, Nuke, After Effects & Premier Pro. Occasional Sunday afternoon DOP. Developer of Cinelog-C Colorspace Management and LUTs - www.cinelogdcp.com

zz77yy

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Re: Slightly darker image after importing into Resolve
« Reply #11 on: November 09, 2017, 02:27:07 AM »
Hi everyone, thank you for your tips and help.

I'm shooting 14 bit.

I tried the different timeline colour space settings and that didn't have much effect.

After Levas comment "are you sure you're getting much more noise when compensating" and Andy 600's comment about ACR applying a curve, I decided to test side by side ACR and Resolve. I pushed the image to where I'd want it, and found that yes infact the noise looked the same in closeups from both ACR and Resolve once they were at a matching exposure.

So at a quick conclusion, ACR is applying a tone curve that makes the image appear brighter, and Resolve is not.

Perhaps I need to look at my actual shooting technique as opposed to post-production? I am only new to ML Raw (I have shot 3 jobs on it), and being able to have the increased dynamic range has been fantastic for the type I've work I've been shooting, but compared to shooting H264, I have found I've had to use pretty heavy noise reduction settings on basically everything with raw, even if shot at 100 ISO. with H264 I generally only need to use noise reduction when I'm getting up to 1600 ISO. I've tried exposing more for shadow areas but then found I'd lose highlight info. So I've basically just been exposing for the subject and its gives me and all round excellent image, I can pull back highlights really nicely, but if I want to lift the shadows then I get lots of noise.

I looked at auto ETTR, but not being able to set the shutter speed means I basically can't use it, unless there's something missing here? I don't want shutter speeds of 1/500 for a 25fps timeline.

Any ideas?

Just incase it is something in my post-processing workflow, I've uploaded a DNG sample file here: https://we.tl/fvddjrrWaK
The DNG has just been processed from MLV to DNG by Switch with no settings changed.

Thanks again :)




bpv5P

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Re: Slightly darker image after importing into Resolve
« Reply #12 on: November 09, 2017, 10:36:11 AM »
I looked at auto ETTR, but not being able to set the shutter speed means I basically can't use it, unless there's something missing here? I don't want shutter speeds of 1/500 for a 25fps timeline.

In this case you should use a ND filter (if you don't want to close your lens aperture). You can also do ETTR manually, for best results. Get the raw histogram from global draw menu. Set your shutter speed (for 25fps you should have minimum of 1/50), the aperture and then using the ISO get the exposure as high as you can (in most high-end cameras you can push as high as +2 f-stops). The image should have much less noise that way.
ISO higher than 600 will probably have bad noise anyway, doesn't matter your technique. In this case, a post-production denoise filter would help (or get artifial lights on the scene).