Resolve & Colour line · stop 04 of 14 · 24 min · members
What a CST is really doing, why the order matters, and the two settings people get backwards.
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What it is
Confusing the two is why people end up fighting their own footage.
A colour space transform converts an image from one defined encoding to another. It is arithmetic with a correct answer, and it has nothing to do with taste.
A look is a creative adjustment. It has no correct answer and it belongs on top of a correctly transformed image.
The confusion arises because a creative LUT also changes how the image appears, and applied to log footage it produces something that looks broadly right. It is not right, it is coincidentally acceptable — and it stops being acceptable as soon as the source or the deliverable changes.
The two halves
They describe different things and people routinely set one and forget the other.
Colour space — also called the gamut — defines which colours the numbers can represent. It is the size and shape of the container.
Gamma — the transfer function — defines how the numbers map onto brightness. It is how the container is filled.
A transform needs both, for both input and output. Getting the gamma right and the gamut wrong gives you correct contrast with shifted colour, usually visible in saturated reds. Getting the gamut right and the gamma wrong gives you correct colour with wrong contrast.
Both symptoms look like grading problems and neither is.
The chain
The middle stage is where all your grading happens.
In — from the camera's encoding into a wide working space. This is the first transform and it belongs on the timeline, above all clips.
Work — all grading happens here, in a space large enough that corrections have room before anything clips.
Out — from the working space to the deliverable. The second transform, also on the timeline, applied last.
Grading directly in the delivery space is the common shortcut and it costs you highlight roll-off and saturated colour, because every push happens against the edges of a small container.
The two reversals
These are the mistakes that produce an image that is nearly right.
Reversal one: input and output swapped. Setting the camera's space as the output rather than the input produces an image that is obviously wrong — usually extremely contrasty or extremely flat. Easy to spot, and worth checking first when something looks badly off.
Reversal two: tone mapping on the input. Tone mapping compresses a large dynamic range into a smaller one. It belongs on the output transform, where it does its job once at the end. Applied on the input, it crushes the range before you have graded, and the highlight detail is gone before you reach for it.
The second is the subtle one. The image looks fine and you simply cannot recover highlights that were discarded upstream.
Doing it twice
Three mechanisms exist, and nothing stops you using two.
A transform can be applied through project-level colour management, through a transform node, or through a conversion LUT. Using two produces a double transform, and the result is over-contrasty in a way that is hard to name.
Choose one mechanism per project and disable the others. Explicit nodes with project management set to a neutral mode is the version that travels best between machines and is easiest to inspect.
Diagnostic: bypass every clip grade. With only the transforms active, the image should look like a slightly flat but entirely normal picture. If it looks wrong at that point, the problem is the transform chain, and nothing above it will fix it.
Why it is worth understanding
Copied settings work until the job changes.
Most people carry a transform setup copied from a tutorial. It works for the camera and deliverable it was written for, and it fails silently when either changes — a second camera, an HDR deliverable, a different gamma request from a broadcaster.
Understanding the chain means those changes are a setting rather than a crisis. New camera: change the input. New deliverable: change the output. Everything between stays as it was.
That is the practical return on twenty minutes of theory, and it arrives the first time someone hands you footage from a camera you have never graded.
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