DNG Explained by Dan Hudgins
August 30, 2014 at 8:24 pm #704
First, as far as I know the DNG are 12bit linear data, the 14 bit rating is for the gross dynamic range in the binned mode, as far as I know, if you send me a 4K DNG I can trace the header and know for sure, I don’t have the 4K KineMINI model here to check things with.
I have been talking with Resolve about having it have a check box so that it would use its fixed conversion plus EV adjustment for the cameras ISO, to do that I have to figure out the relationship between the default EV=0 BM camera setting and what ISO curve that is equivalent to in each KineMINI 4K or KineMAX 6K camera, and the other option would be to automatically load the right shot folder LUT and correct the footage for monitoring matching.
You don’t need to fear clipped anything if the data is loaded right as ALL the monitoring tables I made are softclip and already have the levels adjusted so that ADC max is within the data range.
There is a setup menu in the camera that sets the output range for the shots monitoring matching 3D-LUT, it has these options.
1) Use default setting,
1a) KineCOLOR = Full range by default (not Rec709 legal limits so you need to import this correctly, of set the range limits below)
1b) Kine709 = legal limits for Rec709 set AFTER the monitoring path in the 3D-LUT output, so the BMP snapshot would be full range.
(Kine709B is limited range IN the monitoring path so the BMP snapshot would limited and the 3D-LUT would be default to full but the data would be limited within the full output setting)
1c) KineLOG = Full range with levels above 685/1023 (90% white) are in the super white range and not soft clipped (see the soft clip option below for KineCOLOR)
2) Rec709/HD Range limits with midtone at 46%, this is higher than normal for Rec709 and was included for people with darker skin tones. This can be applied to KineCOLOR and Kine709 but not Kine709B.
3) Rec709/HD Range limits with midtone at 40.7% which conforms to normal signals for Rec709 use. This can be applied to KineCOLOR and Kine709 but not Kine709B.
4) Cineon film log softclip, this converts KineCOLOR and Kine709 and other full range look groups such as KineWIDE, KineMEDIUM, and KineNARROW to film log with softclip so that the data range is within 95/1023 to 685/1023.
Unless you need those functions, set the option to default from LK5 flag, which is full range except for Kine709.
I was told that Resolve used fixed gain on import of DNG files that lack the BaselineExposure tag. I have sent an email to Cheng about adding that tag.
As things stand now, the ISO curve setting will not impact any DNG loaded into Resolve. Also the look group will not impact any DNG loaded into Resolve.
If Resolve fixes these issues, then everything will work right, but I am not sure when that might happen.
If Cheng adds BaselineExposure tag to the Kinefinity DNG header, then mid-tone will center correctly, apparently, as it does with the BM cameras.
For now, if you shoot 800! ISO curve in the KineMINI 4K you can find a constant “brightness” (gamma) correction factor to relate that ISO curve to what is the default for BM cameras in Resolve. If you use the 400! ISO curve the results will look light, if you use the 1600! ISO curve the results should look dark, as I understand what they told me.
I will be checking these issues and trying to develop a table of EV correction factors to apply to the BaselineExposure tag in the Kinefinity DNG header.
That may take some time to implement and would require a firmware update for the camera, you load new firmware through the USB port.
If you try to correct using the Resolve linear option, then you need to apply the linear to cineform_log90 LUT first, then the monitoring matching 3D-LUT which will have the output limits mentioned above included if the were selected.
So you may need two passes, through their LUT, maybe you can set-up “nodes” in their color correction to do that.
Its better for the cineform_log90 LUT to be 1D-LUT as that has more points, which is why they are not combined into a single LUT.
It may be possible to combine BOTH LUT into a single 3D-LUT with 64x64x64 values and get usable results for speeds in the center of the ISO curve range, for 2560 there may be some issue with the shadows, but perhaps not so bad that later grading can’t fix it.
There are probably tools that can combine LUTs, I am working on these things in my free programs, but those features are not released yet.
I was working on a fully automatic solution for the DNG processing and have partial support, but Jihua changed the OLPF and put off all my color calibrations two years ago, then has since changed the OLPF again, so what I have is not fully calibrated for the current cameras as I had planned, and I don’t have one of the current cameras to re-calibrate everything, which can take months with all the combinations.
The K value menu does BURN IN the white balance to the raw data, so it will impact both the Cineform and DNG workflows.
I got some 4K files from Kinefinity that were not white balanced in the data, so their auto-white balance may only impact the monitoring and monitoring matching and set the raw data to native balance, I don’t know that for sure, but its something to look out for in case you see greenish results.
Hope that fills some of the holes, if you ask one question at a time its easer to answer, and eventually you will at least know what should be going on.’
The ISO/EI mode that lets you select the ISO curve will only have one curve for KineLOGC, KineLOGF and so on because I only made the ISO 800 curve for those groups, later it was intended to fill in the other LK5 for those groups.
Only look groups Kine709, KineCOLOR, and KineLOG are full sets in 1/3 stop between 80 and 2560.
You can use analog gain on the others that are only 800 curve now to get 800 (1x green analog gain) to 51200 (64x green analog gain).May 23, 2015 at 3:23 pm #878
All right, first of all, thank you for the amount of effort put into this explanation, Dan.
BUT! Even being tech-minded enough (I always build my PCs myself for instance) this is way too complicated for someone even with experience (I was starting off with Panasonic DVX100).
So what I’m trying to say here, can you point me at some reads, books or something? I mean I want to wrap my head around LOG, DNG and all that stuff because at the moment I have no idea what’s going on inside this Kinemini box.
I mean, how did you learn all this stuff? Maybe you should do some video course on this, because all the courses are like «just choose this option if you want to shoot LOG and that’s it». No it’s not, I don’t need the WHAT, I need the HOW and WHY.
Thanks again, appreciate the effort.July 15, 2015 at 10:17 am #879
Dave ChinParticipantFebruary 1, 2017 at 4:36 am #880
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