How do you sync masks between photos in Lightroom Classic when the composition doesn't match?

By David · September 7, 2026 · 7 min read

I build Lightroom Classic plugins, and the question I get by email most about masks is some version of: "I synced my edit to a batch of photos and the sky mask is now covering half a mountain." The short version is that Lightroom's Local Adjustments syncing does two very different things depending on which kind of mask you're moving - and the type most people assume is "smart" about it, Select Subject and Select Sky, is currently the one most likely to misbehave.

Here's what's actually happening under the hood, which mask types you can trust to sync cleanly, and what to do when the composition on your target photo doesn't match the one the mask was built on.

Why does copying or syncing masks break when two photos have different compositions?

It comes down to how each mask type stores its data. A brush mask is a path of points. A linear or radial gradient is a position, angle, size, and feather. A range mask (color, luminance, or depth) is a set of sampled values from the source photo. None of that is aware of scene content - it's just numbers relative to the frame. When Lightroom pastes those numbers onto a different photo, they land in the same relative position on the canvas, whether or not anything meaningful is actually there.

If your two photos were shot from the same tripod position with the same lens and framing, this is invisible - the geometry lines up because the compositions match. Change the crop, the focal length, or where the horizon sits in the frame, and a sky mask built for one photo starts covering trees in the next. This is exactly the case Adobe built AI masking to solve: instead of storing fixed geometry, Select Subject and Select Sky are meant to store an instruction - "find the sky in whichever photo this lands on" - and recompute it fresh each time.

Which mask types recompute per photo, and which just paste raw geometry?

In theory that table has one clean winner. In practice, AI masks are the row that causes the most confusion, because they're supposed to be composition-safe and frequently aren't - not because the design is wrong, but because of a real bug in current Lightroom Classic releases, covered next.

What does Lightroom's "Local Adjustments" checkbox in Copy Settings actually copy?

Open the Copy Settings dialog (Cmd+C / Ctrl+C in Develop) and you'll find a Local Adjustments checkbox alongside all the other setting categories. Check it, and every local adjustment mask on the source photo - brush, gradient, range, and AI masks alike - transfers as one bundle. There's no way to include only some mask types and exclude others from that dialog; it's all-or-nothing.

If the target photo already has its own local adjustments, Lightroom asks whether to Merge the incoming masks with the existing ones or Replace them entirely. Merge is almost always what you want when you're layering a new look onto a photo you've already partially edited; Replace is for a clean slate.

Here's the part that catches people out: since Lightroom Classic 11.4, AI masks are meant to auto-recompute the moment they land on a new photo via Copy, Paste, or Sync - that's the whole point of storing them as an instruction rather than geometry. But recent Lightroom Classic versions have a documented regression where that automatic recompute stops firing during sync. Instead of quietly re-detecting the sky on each target photo, the mask just sits there showing the source photo's geometry - which looks, and behaves, exactly like a manual mask that wasn't repositioned. Adobe's own community forums have an open feature request and multiple bug threads about exactly this.

Workarounds inside stock Lightroom Classic

None of these fix the underlying bug, but they get you a correct result without leaving Lightroom.

1. Force the recompute manually. Select the photos in Library Grid view (press G first) and choose Photo > Develop Settings > Update AI Settings. On one photo, click Recompute directly on the mask in the Masking panel.
2. Apply through a Develop Preset instead of Copy/Sync. AI masks recompute automatically when applied via a saved preset - a different code path from Copy Settings and Sync Settings.
3. Re-run the AI select tool on the target photo. For a handful of photos, just click Select Sky (or Subject, or People) fresh on the one that's wrong.
4. Oversize manual masks before syncing. Build a brush or gradient mask slightly larger than needed on the source. A shifted-but-oversized mask is easier to trim down than one that lands short.

When you need true re-segmentation on a mismatched photo: built-in options vs. plugins

For occasional cases, Update AI Settings and re-running Select Subject on individual photos is enough. Two situations push people toward a plugin instead: syncing local adjustments across photos with genuinely different orientations, crops, or formats, or wanting to move one specific mask - not the whole local-adjustments bundle - to a differently composed photo.

John R. Ellis's Copy Settings plugin ($9.95, 30-day free trial) replaces Lightroom's built-in Copy/Paste and Sync commands and fixes bugs in how local adjustments, crops, and transforms carry over between photos shot in different orientations or formats - a solid choice if your problem is reliability across a large batch.

If your problem is narrower - one mask off one photo, correctly re-segmented on a specific target rather than pasted at fixed geometry - that's the case I built Look Slots' per-mask copy dialog for.

Frequently asked questions about syncing masks in Lightroom Classic

Do AI masks like Select Subject recompute when I sync settings to a different photo?

They're designed to, but current Lightroom Classic versions have a documented bug where AI masks (Select Subject, Sky, People, Background, Objects) stop auto-recomputing during Sync or Copy/Paste and just sit on the source photo's geometry. Force a recompute with Photo > Develop Settings > Update AI Settings (Grid view, for a whole selection), or click Recompute on the mask itself.

Why does my brush or gradient mask look wrong after I paste it onto another photo?

Brush, gradient, and range masks store fixed geometry - points, position, angle, size, sampled color or tone values - with no awareness of scene content. If the target photo is framed differently, that geometry lands in the wrong place. Drag the mask's pin or points to reposition it manually after pasting.

Does checking Local Adjustments in Lightroom's Copy Settings dialog copy every mask?

Yes. The checkbox transfers every local adjustment mask on the source photo as one bundle - you can't pick individual masks to include or exclude. If the target photo already has its own masks, Lightroom asks whether to Merge the incoming masks with the existing ones or Replace them entirely.

Is there a way to sync only the AI masks and skip the manual ones, or the reverse?

Not with Lightroom's built-in Copy Settings or Sync Settings - the Local Adjustments checkbox is all-or-nothing. John R. Ellis's third-party Copy Settings plugin adds more granular control and fixes several long-standing bugs in how Lightroom copies local adjustments between differently oriented or formatted photos.

What's the fastest way to get an accurate mask on a photo with a different composition?

For a handful of photos, re-run Select Subject or Select Sky directly on the target. To pick one specific mask off a source photo and place it correctly on a differently composed target, Look Slots' per-mask copy dialog re-segments AI masks on the target instead of pasting the source's raw geometry.