Three Deliverables, One Night

The fringing is an alpha-type mismatch, not an edge-quality problem.

Elements to check, in order:

1. Channels. The output module must be RGB + Alpha. If it was RGB only, you have a flattened file and the editor is keying something else entirely.
2. Codec capability. ProRes 4444 carries alpha; the 4:2:2 variants do not. A codec without an alpha channel produces exactly the halo the editor is describing once the NLE invents a key.
3. Premultiplied vs straight. After Effects renders premultiplied against black by default. If the output was set to Straight and the editor's NLE assumes premultiplied, every semi-transparent edge darkens; the reverse gives light halos. Align the output module setting with how the receiving application interprets alpha, and state it in the delivery note.
4. Background. The comp must have no opaque background layer for the alpha version. A background solid makes the file fully opaque and the fringing report becomes irrelevant because there is nothing to key.
5. Depth. Keep the render at 16 bpc so the soft edges carry real intermediate values; 8-bit alpha edges quantise and shimmer.

Practical delivery: produce the alpha master as ProRes 4444, RGB + Alpha, premultiplied, 16 bpc, full resolution, at comp frame rate. Also send a one-page note stating codec, alpha type and color space, so the next person does not have to guess.

Why it bands. A smooth dark-to-mid gradient has very few distinct values per channel. Encoding to 8-bit 4:2:0 with chroma subsampling and a modest bitrate collapses those steps into visible bands, especially on the platform's own re-encode.

Fixes, cheapest first:

1. Render the web file from the 16-bpc comp with maximum bit depth enabled and a high-quality, two-pass H.264 encode at a generous bitrate. This alone removes most of it.
2. Add a very small amount of noise or grain (roughly 1 to 2 percent) to the web comp before encoding. Dithering breaks the flat steps into noise that the encoder handles far better than a mathematically smooth ramp.
3. Rebuild the gradient with a slight texture or a subtle vignette rather than a pure linear ramp, if the design allows.

What not to do: do not add the dither or grain to the graded master and do not lower the master's bit depth. The broadcast master should stay clean and 16 bpc; the noise is a delivery-specific treatment living in a separate output comp or an adjustment layer that is switched off for the master render. Mutating the approved master to fix a web artefact creates a re-delivery problem later, and grain on a broadcast master may simply be rejected.

Also confirm the H.264 is not being scaled or letterboxed on the way out; scaling a gradient after the fact reintroduces banding.

Plan.

1. Transparent version: render it as ProRes 4444 RGB + Alpha straight from After Effects, the same settings family as the master. It has to be a real render because the alpha is comp content, and it can run in the same batch as the master if the master is being re-rendered anyway.
2. Web version: render directly from the project at maximum depth rather than transcoding the ProRes master. Transcoding is faster but inherits the master's full-range RGB to limited-range YUV conversion and any banding already present, and it gives you no chance to apply the dither fix. If time genuinely runs out, transcode but expect to redo it.
3. Batch them in one render queue or one Adobe Media Encoder queue from the same project, so all three share one set of comp settings and one color pipeline.

Traps:

• H.264 cannot carry alpha. Do not promise a transparent H.264; offer ProRes 4444, PNG sequence or an embedded matte instead, and ask the sister agency which their NLE reads.
• Proxies and draft settings left on from the review pass silently soften all three deliverables.
• Output naming and post-render actions: set explicit output paths per item so a batch render does not overwrite the master.
• Disk and cache pressure with three 45-second 16-bpc renders queued at once; clear the disk cache and confirm free space before starting, or the last item fails at 95 percent.
• Color pipeline consistency: whatever output color handling the project uses must be identical for all three files, or the client will see two different-looking deliverables and blame the grade.