- Posts: 49
- Joined: Mon Jun 29, 2020 12:18 am
- Real Name: Devon Stanczyk
I have noticed a “bug”. I'm not sure if it's existed for a long time or not. This is a "bug" that may affect folks shooting cinema DNG.
Apologies in advance for the lengthy post.
We had a shoot with 4 different cameras. 3 BM 6k pros, and a Sigma FP. I noticed that some of the footage from the Sigma FP was harder to white balance than other clips shot on the FP. After chatting with the camera op and reading the metadata in EXIFTOOL, it seems our camera op was changing between some of Sigma's in-camera color modes during shooting. All clips were shot UHD cDNG 12bit.
So I did a test.
The results of the test are a little concerning (at least for the sake of color consistency.) See images in this post. I will also post a link to my Davinci Project file, and single DNG frames from my tests.
I set up a few objects in my apartment to capture different colors (apologies for not having a true color checker chart.) A green painting, white foam core board, a red roll of tape, and a yellow hat. I literally had nothing blue to film, but the painting has a little blue in it. I wasn’t testing for color ACCURACY, as much as I was testing for color CONSISTENCY. Everything is lit by a single source. No house lights were on, and I blacked out all windows to make sure everything was lit by a single source for consistent color and exposure. The Sigma FP was mounted on a tripod, all camera settings & lens stayed exactly the same for each clip, EXCEPT I changed the in-camera color mode. All clips shot UHD cDNG 12bit.
This is where our “bug” is. It's either Sigma FP in-camera color modes, or Davinci Resolve cDNG debayering. I have noticed that shooting clips (CinemaDNG/RAW, every resolution and frame rate) with ANY color mode activated EXCEPT color mode “OFF”, exhibits the same color shifts in Davinci Resolve.
It has always been my experience that in-camera color modes (regardless of manufacturer) DO NOT affect how RAW data debayers in post. It’s always been, “RAW is RAW.” “Sensor data is sensor data.”
SO, I shot a clip for each Sigma color mode. What I found is that color-mode: “OFF” produced footage as expected. It balanced very easily, and felt natural. BUT any clip shot with ANY other color-mode activated, exhibited color imbalance/shifts.
In DaVinci Resolve, I balanced the in-camera color mode “OFF” clip, to make the white foam core in the frame neutral. White balance adjustments were done in the RAW panel on the color page. I then applied that same grade to all other clips. Every clip was debayered as P3-D60, linear. White balance stayed the SAME between each clip to show the color shift. In my node graph, I then color space transformed from P3-D60, linear, to REC709, REC709 (timeline color space was REC709-A). Tone mapping set to “None”. I did simple Lift gamma gain adjustments for contrast, added saturation, then soft clip to keep things from clipping (all on separate nodes.) Again, the very exact same RAW panel settings, and nodes were applied to each clip.
Still curious, I opened the DNG’s in Adobe Camera RAW. Adobe Camera RAW DID NOT exhibit the same balancing issues as Davinci Resolve did. Both DNG’s debayered identically in Adobe Camera RAW/Lightroom. This possibly means that the RAW sensor data between “OFF” clips and activated color mode clips, has consistency. I suspect there’s something in the DNG metadata throwing things off in Davinci Resolve. SO, I had another idea to convert camera original DNG’s using Adobe DNG Converter. Lo and behold, after conversion using Adobe DNG Converter, both clips were visually identical when imported and debayered in Davinci Resolve. In fact, the Adobe DNG Converted DNG's very closely resembled the color mode "OFF" original. (Adobe DNG Converter removes some Cinema DNG metadata like frame rate, timecode, and also reports “16 bit” color depth, among other things. It strips this data because Adobe's DNG Converter is ultimately meant for photographers.) Since Adobe DNG Converter strips metadata, it must be stripping the metadata that is causing Davinci Resolve to debayer clips differently.
EXIFTOOL shows a few differences between FP original DNG’s. Although I’m not a software engineer, so which metadata tag is causing the issue requires someone smarter than me. I will leave out the EXIFTOOL reports since this post is already very lengthy. Happy to post EXIFTOOL reports if it helps.
The ultimate question is: Is this behavior caused by Sigma, or is this a "bug" within Davinci Resolve?
DNG's and Davinci Resolve project files here: https://www.mediafire.com/file/lf9jmvqz ... r.zip/file
Apologies in advance for the lengthy post.
We had a shoot with 4 different cameras. 3 BM 6k pros, and a Sigma FP. I noticed that some of the footage from the Sigma FP was harder to white balance than other clips shot on the FP. After chatting with the camera op and reading the metadata in EXIFTOOL, it seems our camera op was changing between some of Sigma's in-camera color modes during shooting. All clips were shot UHD cDNG 12bit.
So I did a test.
The results of the test are a little concerning (at least for the sake of color consistency.) See images in this post. I will also post a link to my Davinci Project file, and single DNG frames from my tests.
I set up a few objects in my apartment to capture different colors (apologies for not having a true color checker chart.) A green painting, white foam core board, a red roll of tape, and a yellow hat. I literally had nothing blue to film, but the painting has a little blue in it. I wasn’t testing for color ACCURACY, as much as I was testing for color CONSISTENCY. Everything is lit by a single source. No house lights were on, and I blacked out all windows to make sure everything was lit by a single source for consistent color and exposure. The Sigma FP was mounted on a tripod, all camera settings & lens stayed exactly the same for each clip, EXCEPT I changed the in-camera color mode. All clips shot UHD cDNG 12bit.
This is where our “bug” is. It's either Sigma FP in-camera color modes, or Davinci Resolve cDNG debayering. I have noticed that shooting clips (CinemaDNG/RAW, every resolution and frame rate) with ANY color mode activated EXCEPT color mode “OFF”, exhibits the same color shifts in Davinci Resolve.
It has always been my experience that in-camera color modes (regardless of manufacturer) DO NOT affect how RAW data debayers in post. It’s always been, “RAW is RAW.” “Sensor data is sensor data.”
SO, I shot a clip for each Sigma color mode. What I found is that color-mode: “OFF” produced footage as expected. It balanced very easily, and felt natural. BUT any clip shot with ANY other color-mode activated, exhibited color imbalance/shifts.
- DNG-01.png (589.45 KiB) Viewed 3307 times
In DaVinci Resolve, I balanced the in-camera color mode “OFF” clip, to make the white foam core in the frame neutral. White balance adjustments were done in the RAW panel on the color page. I then applied that same grade to all other clips. Every clip was debayered as P3-D60, linear. White balance stayed the SAME between each clip to show the color shift. In my node graph, I then color space transformed from P3-D60, linear, to REC709, REC709 (timeline color space was REC709-A). Tone mapping set to “None”. I did simple Lift gamma gain adjustments for contrast, added saturation, then soft clip to keep things from clipping (all on separate nodes.) Again, the very exact same RAW panel settings, and nodes were applied to each clip.
Still curious, I opened the DNG’s in Adobe Camera RAW. Adobe Camera RAW DID NOT exhibit the same balancing issues as Davinci Resolve did. Both DNG’s debayered identically in Adobe Camera RAW/Lightroom. This possibly means that the RAW sensor data between “OFF” clips and activated color mode clips, has consistency. I suspect there’s something in the DNG metadata throwing things off in Davinci Resolve. SO, I had another idea to convert camera original DNG’s using Adobe DNG Converter. Lo and behold, after conversion using Adobe DNG Converter, both clips were visually identical when imported and debayered in Davinci Resolve. In fact, the Adobe DNG Converted DNG's very closely resembled the color mode "OFF" original. (Adobe DNG Converter removes some Cinema DNG metadata like frame rate, timecode, and also reports “16 bit” color depth, among other things. It strips this data because Adobe's DNG Converter is ultimately meant for photographers.) Since Adobe DNG Converter strips metadata, it must be stripping the metadata that is causing Davinci Resolve to debayer clips differently.
- DNG-02.png (578.71 KiB) Viewed 3307 times
EXIFTOOL shows a few differences between FP original DNG’s. Although I’m not a software engineer, so which metadata tag is causing the issue requires someone smarter than me. I will leave out the EXIFTOOL reports since this post is already very lengthy. Happy to post EXIFTOOL reports if it helps.
The ultimate question is: Is this behavior caused by Sigma, or is this a "bug" within Davinci Resolve?
DNG's and Davinci Resolve project files here: https://www.mediafire.com/file/lf9jmvqz ... r.zip/file