If you’re not sure what a Look-up Table (LUT) is, start by reading What is a LUT?.
The ‘two’ two kinds of LUTs you can create
There are two kinds of LUTs you can create:
- 1D LUT
- 3D LUT
You can create both kinds in DaVinci Resolve. However, there are two other kinds of LUTs you can create in Resolve:
- The Soft Clip LUT (Either 1D or 3D)
- The ‘normal’ 3D LUT
To make it simpler, Blackmagic Design recommends that you use a 1D LUT for the Soft Clip LUT:
1D LUTs are more accurate for this operation, using 1023 data points, as opposed to the 33x33x33 cube of the 3D LUT.
So, to make your life simpler, follow this rule of thumb:
- Soft Clip LUT – 1D LUT
- 3D LUT for everything else
Now all that remains is to understand the difference between a 3D LUT and a Soft Clip LUT.
3D LUT vs Soft Clip LUT
The Soft Clip LUT is a special LUT that does everything a regular LUT does with two extra goodies:
- Forced highlight/shoulder roll-off so your white clipping looks more pleasing.
- Forced shadow/toe roll-off so your black clipping looks more pleasing.
To know what the shoulder and toe is, read this.
When would you need such a LUT? After all, you can see the results of your grading on the monitor anyway, can’t you? Yes you can, and I recommend that is the best way to proceed. But this also means you must have a good eye on your scopes.
However, sometimes you have no time or budget or resources to grade using all the features available. You might just want to ensure your video falls within broadcast specifications (specifically Rec. 709) without worrying about hard clipping. If you just clamp down the whites and blacks to studio swing, the blacks and whites might clip abruptly, with undesirable ‘video-y’ effects.
When would you use a Soft Clip LUT? You would use it in the Output LUT setting as the final step in the grading process. It is NOT recommended to replace a grading or 3D LUT, but only to control the highlight-shadow rolloff.
Let’s see how to use it.
How to create Soft Clip LUTs in DaVinci Resolve
There are two ways you can proceed here. You can either:
- Just do a highlight-shadow roll-off and nothing else.
- Have a grade/LUT ready and apply the highlight-shadow roll-off along with it to create a new LUT.
If you have a grade already, create a LUT first as shown in the next section. Then, go to Project Settings > Color Management:
Click on Update Lists. If your LUT doesn’t show up, you might have to restart Resolve.
Once your LUT is visible, scroll down to the Generate Soft Clip LUT section:
As recommended, select 1D lookup table under Generate.
If you have a LUT you want to combine with the operation, select it under Generate LUT based on:. If you don’t have a LUT and just want to control highlight-shadow roll-offs, then leave it at No LUT selected. The other two options are:
- Data to video with clip – Resolve has two clip level attributes – data (full swing + super whites) and video (studio swing). This is standardized to the levels given below so is a bit redundant.
- Invert color – inverts the colors so you can see what the LUT is doing, if it is doing anything at all. Just a verification step when you have complex grades and nodes.
Check Scaled to clipping range if you want to hard clip. This will disable the softness percentage options (more later). Curiously, the manual is not very clear:
Scaled to clipping range: Enables the Maximum and Minimum settings below to work.
When you apply a LUT along with the clip effect, you lose control over the softness.
Whether your project is in 8-bit or 10-bit, you must specify the video levels based on 10-bit only. For studio swing, these values are:
- White (Maximum video level): 940
- Black (Minimum video level): 64
Don’t input 235 or 16 (8-bit values) even if your project is in 8-bit. It will clip on these values in the 1024 scale!
Now’s the tricky part. The softness percentages for Upper Clipping and Lower Clipping must be selected. If it were so simple, we would have one standard LUT and that would be that. However, different cameras deal with highlights and shadows in different ways. In addition, the ISO you select, how you choose to expose, etc., will all play a part in how your highlights and shadows fall on your gamma curve.
This means, you must select these percentages based on how the footage looks once it has been ‘soft’ clipped. The process is:
- Create the Soft Clip LUT.
- Apply it on your footage.
- Study the scopes to ensure values fall within the legal range.
- Study your footage in the viewer through a calibrated broadcast monitor in 10-bit, or 8-bit if that delivery mode is acceptable.
- If this last step look okay, you’re good to go. Otherwise, change the percentages and create another soft clip LUT and repeat until you’re satisfied.
- Do this for all your footage and study them one by one to ensure nothing is ‘out of place’. If it is, rinse and repeat specifically for just those clips.
Now you know why I’m not a fan of this process. You’ll be doing this anyway if you’re grading. If you don’t have the time, budget or infrastructure for professional grading, what use is the Soft Clip LUT anyway? You decide.
Finally, enter the name of your LUT in Save LUT as: and click on Generate LUT. Your LUT is created, and no confirmation is given. To know where it has been saved, read the last section in this article.
How to create a 3D LUT in DaVinci Resolve
For complex grades, you must ideally generate a 3D LUT. This is not mandatory. If you’re just creating LUTs for dailies or monitoring purposes, a 1D LUT is standard.
To generate a 3D LUT, while you’re on the Color page itself, right-click on the thumbnail in the ‘Compressed’ timeline and select Generate 3D LUT:
Where and how are LUTs saved?
LUTs are not always stored where you expect them to be. From the Resolve manual:
- Mac OS X: Library/Application Support/Blackmagic Design/DaVinci Resolve/LUT/
- Windows: C:ProgramData/Blackmagic Design/DaVinci Resolve/Support/LUT
- Linux: /home/resolve/LUT
What formats are supported? Resolve writes to (and can of course, read) the *.cube format. This is also supported by other NLEs and applications. Resolve also reads LUTs in the Cinespace and Shaperlut formats.
That’s it! Creating LUTs in DaVincie Resolve (Amazon, B&H) is simple and straightforward, as long as you understand the nuances of soft clipping LUTs. Most of the time, you’ll be creating 3D LUTs for general purpose work and color grading.