S-Log3 to Rec.709 in Final Cut Pro, step by step

Final Cut Pro applies a Sony S-Log3 LUT on import without being asked, which is convenient right up until a library setting quietly caps your dynamic range. Here is what each control actually does, and the order that keeps it from working against you.

Confirm the Camera LUT (it is probably already on)

Final Cut Pro reads log metadata on import and applies the matching built-in Camera LUT automatically; Sony S-Log3 is one of the profiles it recognizes. To confirm or change it, select the clip, open the Info inspector, click the Metadata View pop-up menu in the bottom-left corner and choose Settings, then use the Camera LUT pop-up. Choosing None turns log processing off entirely, which you would only want if you are correcting the clip some other way.

Set the library to Wide Gamut HDR first

This is the step tutorials skip. A Camera LUT only preserves S-Log3's full dynamic range when the library's color processing is set to Wide Gamut HDR. On Standard (or the deprecated Wide Gamut setting), Final Cut tone-maps the log media down to SDR before the LUT does its work, and you lose highlight and shadow detail you will never get back. Check it under File > Library Properties > Modify, before you grade anything.

Color Conform, on by default, then matches each clip's color space to the project automatically as it lands on the timeline. You can switch it to Manual per clip in the Video inspector if a specific clip needs an override, but for a normal S-Log3 wedding shoot, leave it on Automatic and let the Camera LUT do the actual conversion.

White balance and exposure, in that order

1. White balance with the eyedropper. In the Video inspector's Balance Color section, choose White Balance from the pop-up and click a neutral white or gray area of the frame, a well-lit shirt or wall, not a blown highlight. This removes the cast S-Log3 tends to exaggerate under mixed indoor light before you touch anything else.

2. Set exposure on the Color Board. Add the Color Board effect and use its Exposure control against the scopes, aiming skin at roughly 60 to 70 IRE rather than judging it on a bright edit-bay monitor that flatters everything.

3. Match a second camera last. If a second body is in the same project, line both up on the scopes before adding any creative look. Matching after the fact just means redoing the look twice.

Where this order breaks

Wrong library color processing. The most common failure. Everything looks fine until you push highlights or shadows and hit a wall that should not be there. Check Library Properties before you blame the LUT.

Color Conform plus a custom LUT stacking. Apple's own documentation notes that Color Conform and an HDR-oriented effect are additive, so use one or the other on a clip, not both, or you will double-transform it.

The part that is measurement, not taste

White balance, transform, exposure, and cross-camera match are all objective steps, which is why Basecut automates them for a whole card dump at once, locally on your machine. It culls the shoot, corrects S-Log3 (and 15 other log formats) per clip, and hands a matched Rec.709 baseline to DaVinci Resolve, where the creative grade starts. It exports FCPXML so Final Cut can pick up the same bins and tags, but to be direct about the limit: its automated color correction is built for Resolve, not for a Final Cut library, so if Final Cut is where you finish, the steps above are what you are running by hand.

The 14-day trial (5 free exports, no card) is enough to see the correction on your own footage before deciding anything. See it on real footage.