Resolve & Colour line · stop 03 of 14 · 26 min · members
Getting from a flat Sony file to a broadcast-legal image with a transform instead of a lucky curve.
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The problem
It is an encoding, and encodings are undone with maths, not with a contrast curve.
The most common way people handle S-Log3 is to drop a creative LUT on it, then fight whatever the LUT did. It sometimes looks fine. It is never repeatable, and it falls apart the moment you cut in a second camera or deliver to a second specification.
The alternative is to treat the log file as what it is: a known input colour space and gamma that needs to be transformed into a known working space, graded there, and then transformed again into a known output. Three steps, all of them defined, none of them a matter of opinion.
Once the chain is right the image arrives looking broadly correct before you have made a single grading decision — and that is the point.
Step one
S-Log3 and S-Gamut3.Cine are two separate settings, and mixing them up is the usual mistake.
On a Sony body shooting S-Log3, the two values you need are:
S-Gamut3 and S-Gamut3.Cine are different. Cine is the smaller, better-behaved gamut and it is what most people are actually shooting. Choosing the wrong one shifts saturated colour — usually reds — in a way that looks like a grading problem and is not.
Check the camera, not your memory
Sony bodies let you shoot S-Log3 with either gamut. Confirm it in the file's metadata or the camera menu rather than assuming. Two minutes here saves an entire session of chasing a cast that was never in the footage.
Step two
DaVinci Wide Gamut gives your corrections room to move before anything is clipped.
Set the working space to DaVinci Wide Gamut with DaVinci Intermediate gamma. This is where all four of your clip nodes live.
The reason is headroom. If you transform straight to Rec.709 and grade there, every push you make is happening inside the delivery gamut, and highlights and saturated colours clip against its edges. In a wide space they have somewhere to go, and the clipping only happens once at the very end, under your control.
Practically this means a highlight roll-off that looks like film rather than a hard shoulder, and saturated colour that bends instead of flattening into a block.
Step three
Rec.709 with Gamma 2.4 for broadcast, and know why you would ever choose otherwise.
The final transform goes on the timeline node, after everything else:
Enable tone mapping on the output transform rather than the input. Letting it compress the highlights at the end, once, is the whole reason for grading wide.
Sanity check
Bypass your clip grade entirely. With only the two timeline transforms active, the image should look like a slightly flat but completely normal Rec.709 picture. If it looks wrong at this stage, the problem is in the transform, and no amount of grading above it will fix it properly.
The trap
Colour management, a CST node and a conversion LUT will all happily run at once.
Resolve gives you at least three ways to do a colour space transform, and nothing stops you using two of them together. The result is an image that looks contrasty and slightly wrong in a way that is hard to name.
Pick one method and disable the others:
Never both. If you inherit a project that looks over-contrasty, check for this before you touch anything else.
After the transform
When the chain is correct, the creative work stops being rescue work.
The measure of a correct transform chain is how little you have to do afterwards. Exposure moves become small, white balance becomes a nudge, and the look node is doing creative work rather than repair.
If you are still making large corrections on every clip, the transform is wrong somewhere upstream. Go back and check the input gamut before you accept that the footage is difficult.
This chain is also what makes a grade portable. Hand the project to another colourist and the structure explains itself — which is the difference between a project someone can finish and one they have to restart.
1:1 · two hours