What Smart Previews Are
Smart Previews are compressed, lossy DNG proxy files generated from your RAW originals. Each proxy is approximately 2540 pixels on the long edge, small enough to be lightweight but large enough to support full Develop module editing.
Key characteristics:
- Format: Lossy DNG
- Resolution: ~2540 px long edge
- Typical size: 1–2 MB per image
- Stored in: Smart Previews.lrdata bundle next to the catalog
- Editable: Yes — full Develop module functionality
- Sync behavior: Edits made on Smart Previews automatically apply to RAWs when originals reconnect
Smart Previews are not thumbnails, JPEGs, or sidecar files. They are fully functional stand‑ins for RAW files.
Why Smart Previews Exist
Adobe designed Smart Previews to solve three specific workflow challenges:
1. Offline Editing
Photographers often travel without their full archive. Smart Previews allow complete editing even when the originals are disconnected.
2. Faster Performance
Editing a 1 MB proxy is significantly faster than editing a 40–60 MB RAW. Smart Previews reduce disk I/O and improve responsiveness in the Develop module.
3. Lightweight Collaboration
Smart Previews allow a photographer to send a catalog to an editor without shipping terabytes of RAW files. The editor can perform color grading, cropping, and global adjustments, and the photographer can apply those edits to the originals later.
How Smart Previews Work Inside Lightroom
Lightroom uses a simple decision tree:
- If RAW is present: Lightroom edits the RAW.
- If RAW is missing but Smart Preview exists: Lightroom edits the Smart Preview.
- If neither is present: Develop module is disabled.
When both RAWs and Smart Previews exist, Lightroom prefers the RAW but keeps the Smart Preview available for performance acceleration. This is why some photographers build Smart Previews even when originals are present.
Smart Previews vs. Standard Previews
These two preview types serve different purposes.
Standard Previews
- Used for Library module browsing
- JPEG-based
- Resolution depends on preview settings
- Not editable
- Stored in Previews.lrdata
Smart Previews
- Used for Develop module editing
- DNG-based
- Fixed resolution (~2540 px)
- Fully editable
- Stored in Smart Previews.lrdata
Standard Previews are for viewing.
Smart Previews are for editing.
Smart Previews and Catalog Exporting
When exporting a collection as a new catalog, Lightroom offers three options:
- Include available previews
- Include Smart Previews
- Include negative files (RAWs)
Smart Previews matter primarily when RAWs are not included. If the exported catalog contains RAWs, Smart Previews become optional.
When Smart Previews Are Essential
Smart Previews should be part of your workflow when:
1. You need offline editing
Traveling with a laptop and leaving the RAWs on a studio RAID? Smart Previews allow full editing.
2. You collaborate with editors
Sending a lightweight catalog to a remote editor is dramatically easier with Smart Previews.
3. You want faster Develop performance
Even with RAWs present, Smart Previews can accelerate editing on slower machines or external drives.
4. You use cloud-based workflows
Smart Previews reduce bandwidth and storage requirements for cloud sync.
When Smart Previews Are Optional
Smart Previews are not required when:
1. Your catalog always travels with the RAWs
If the catalog is self-contained and includes negatives, Smart Previews add no functional benefit.
2. You only need the catalog for archival
If the catalog is stored with RAWs on external drives or cloud storage, Smart Previews are unnecessary.
3. You want faster export times
Building Smart Previews is CPU-intensive. Skipping them speeds up catalog creation.
When Smart Previews Can Be Counterproductive
There are rare cases where Smart Previews may introduce complications:
1. Mixed editing sources
If both RAWs and Smart Previews exist, Lightroom may switch between them depending on file availability, causing slight visual differences during editing.
2. Storage clutter
Smart Previews.lrdata can grow into multi-gigabyte bundles if left unmanaged.
3. False sense of RAW availability
A catalog with Smart Previews but no RAWs appears fully editable, but cannot export full-resolution files until originals reconnect.
Conclusion
Smart Previews are a powerful Lightroom feature that enable offline editing, improve performance, and support flexible collaboration. They do not replace RAWs, but they serve as intelligent, compressed proxies that allow photographers to work anywhere without sacrificing editability.