Cinelog-C for DaVinci Resolve
White Balance - back to basics
The lack of an auto white balance button in the Camera Raw panel of DaVinci Resolve can leave new users scratching their heads in dismay, especially anyone who is used to the one-click controls found in some raw image editing apps.
An auto raw white balance feature would certainly be useful but the lack of one is not particularly an oversight by Blackmagic. DaVinci Resolve is after all, the leading professional color grading app in the world. It is used by professional colorists and guess what? Professionals colorists understand white balance!
So, rather than bemoan the lack of features, let look at adding 'manual white balancing of raw images' to your skillset with these tips and procedures. We will also be using Resolve's scopes - another thing that may be new to some users.
A Good balance in Resolve begins with a good balance in the camera
Jumping into Resolve and balancing an image is actually quite easy - a colorist will typically take only a few seconds to achieve neutral white balance for a group of shots. This ability comes with practice and the more you do it, the easier and quicker it will become.
There will be times when even a colorist will struggle to hit neutral first time. This can be because there is no useable neutral reference in the video to judge what corrections are needed or metadata issues (especially when it comes to Magic Lantern Raw Video) that pass the wrong instructions to Resolve.
So, with that in mind, lets start at the very beginning and look at perhaps the most important way to white balance an image - Get it right in-camera first!
The raw DNG/Cinema DNG images that your camera stores when recording raw does not contain nice color. It has no white balance and it has no colorspace - it is raw pixel data. It is the metadata that is embedded alongside the image (at the time of shooting) that acts as an instruction set to tell the raw viewer, editing app how to translate the pixel values into an image that resembles the captured scene.
As with the previous settings, playback performance may be an issue for some users - if so, select Optimize for playback where it is an option.
Input Scaling offers 4 settings. Here we will select Scale entire image to fit. This will zoom the image to fit the width of the project (in this case 1080 pixels) without causing distortion. If your footage was shot in another aspect ratio (i.e. 2.35:1 etc - as can be set for Magic Lantern Raw Video) your video will be letterboxed with black bars above and below the video. Image scaling and re-framing can be adjusted independently for each separate shot in the job.
Other settings can remain at their defaults. Click Apply and open the next tab - Editing.
We will not alter the default settings for this particular project but just so you remember, this is where you setup Frame Interpolation with Optical Flow for creating smoother slow motion playback from your footage. This is very processor intensive. We will cover this in a later tutorial.
Click the next tab Color
We will leave these settings at default values for this particular transcoding job.
Click the next tab Camera Raw
The Camera Raw panel is where we make some important settings for our transcoding project. As we are transcoding DNG/CinemaDNG images, make the following settings shown in the image opposite. These settings can be altered independently for each clip later but we will set these defaults for now.
Click Apply and open the next tab Lookup Tables
Lookup Tables (LUTs)
Ok, lets apply our first LUTs. The Lookup Tables panel has many slots for different types of LUT and will be used differently for certain projects but for this particular project/template we are only interested in 2 of them (shown in the image below)
Skip the next couple of paragraphs (down to the Audio heading) if you wish - but it's useful information to know.
Our DNG footage will be debayered (also refereed to as demosaicing) to BMD Film colorspace. Several other colorspaces (a workspace with a specific RGB chromaticity, gamma, log or linear transfer) are available in Resolve (from the smallest REC709 to the largest ACES). We are only interested in BMD Film for this job but will look at the purpose and functions of other colorspaces in later guides.
Although BMD Film is a very useful, wide gamut, 32bit floating point workspace when grading raw footage (i.e. color grading with the actual DNG files). We will be transcoding our DNG files to a much more efficient format that is both easy to color grade and quicker to edit (in any NLE, even the ones that do not support the DNG format) whilst retaining as much color information and dynamic range as possible. This is where Cinelog-C comes into play.
We will mathematically transform (remap) the colorspace and log transfer curve of BMD Film to Cinelog-C using a special shaper LUT called (appropriately enough) BMD Film to Cinelog-C. Cinelog-C has slightly more dynamic range than BMD Film but can compress the raw data of your DNG files (using a codec such as ProRes) into a 10bit container - with a much smaller footprint than the equivalent folder of DNG files - this is why it's also a good way to archive large raw projects.
Unlike BMD Film, Cinelog-C has published chromaticities, making it much easier for colorists to conform to/from.
Once transcoded we can (depending on the codec properties selected), retrieve a huge amount of color information and remap the log code values to scene linear values - effectively producing a visually identical copy of the debayered, linear DNG files.
OK, that may be a little too technical for some users to fully appreciate now but over time you will discover the real benefits and power of being able to do this with Cinelog-C in DaVinci Resolve.
- oh, sorry - you're probably wondering what LUTs to use?
For this transcoding job we use [TRANSFORM]_BMD_Film_to_Cinelog-C and [REC709]_Cinelog-C_to_REC709 LUTs in the slots as shown in the image above.
Why? - The 3D Input Lookup Table slot will apply the BMD Film to Cinelog-C transform immediately after debayering the DNG images to BMD Film colorspace. The LUT itself is not a typical 3D cube lut. It has a separate and very high precision 1D shaper component that transfers BMD Film log values to Cineon log values using a 12bit curve - plus a 65x65x65 linear 3D component that only transforms the RGB primaries. This precision is not possible with a conventional 3D lut. The BMD Film to Cinelog-C will be 'baked' into our ProRes or DNxHD video.
The next LUT we apply is not rendered/baked into the video. The 3D Monitor LUT Lookup Table slot is normally used to host a monitor calibration LUT but we will re-purpose for viewing only just for this job.
Judging white balance and exposure while looking at a log image (even using scopes) is not easy or recommended so we will add a second, transient transform from Cinelog-C to REC709 purely so we can see what Cinelog-C will look like when de-logged and viewed in REC709 colorspace. This lut is a conventional 3D lut that does 2 things. It transfers the Cineon log curve to REC709 gamma (with an S-curve) and transforms the RGB primaries from Cinelog-C to REC709.
Other settings in the Lookup Table panel should remain at their defaults and certainly DO NOT select Make Broadcast Safe at this time!
Click Apply and skip the next panel Versions as we do not use it here - Open the Audio panel instead
This setting is self-explanatory - if you have recorded audio select Enable Audio
Click Apply and open the next tab - General Options
OK, nearly done with this section!
For this transcode-only job we will disable Background caching. If you have a powerful system with fast hard disk read/write (i.e. a RAID), Background caching can be left enabled.
Working Folders should be set to your own preferences, relevant to your disk configuration.
We do not need to adjust anything in the remaining panels so we will now save our settings as a re-useable preset/template.
Click on the Presets panel tab and click Save As. Rename your preset according to the settings you selected for the project. In this case I have named it Cinelog-C Transcode 1080p-25p (note: certain characters i.e. / ! @ # etc are not allowed)
You now have a Project template for transcoding 1080p 25fps footage to Cinelog-C.
Tip: You can alter the project settings of this template to different dimensions/frame rates and click Save As again to build a collection of transcoding templates with different settings.
in part 2 we will import our raw footage, set-up a re-useable render job template and transcode our first Cinelog-C log masters.