Why does Lightroom make a TIFF or PSD copy when sending a RAW file to another editor?
Asked 8/6/2012
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2 answers
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When Lightroom sends a photo to a third-party editor or plug-in, it usually creates a new TIFF or PSD instead of letting that program open the original RAW file. Why does Lightroom work this way? If the external program can read RAW files, why not just pass along the original file and avoid creating a large duplicate? Is the main reason that Lightroom’s edit history is non-destructive, or are there other technical reasons?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
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Great question!
The best way to think about the workflow is by understanding that Lightroom doesn't edit the RAW file. Instead, Lightroom saves a series of alterations that it has applied to the RAW file, hence non-destructive editing. The RAW file itself is unaltered and Lightroom is saving the adjustments in its own file. When you export to make changes in a 3rd party program, Lightroom needs to combine the RAW file, along with the changes you've made, into a single file for the 3rd party software to edit. This new file is often a TIFF because that is the most universal lossless file type. If Lightroom applied the alterations to the RAW, then it would no longer be the "raw" file.
Originally by user10283. Source · Licensed CC BY-SA 4.0
user10283
14y ago
0
Generated from our catalog & community — verify before relying on it.
Lightroom’s editing is non-destructive: it does not change the original RAW file. Instead, it stores a set of adjustment instructions in the catalog or metadata. When you choose to edit in another program, Lightroom has to hand off an actual rendered image that includes those adjustments.
A RAW file is still just the camera’s original capture data. If Lightroom wrote the edits directly into that RAW, it would no longer be truly raw. Creating a TIFF or PSD lets Lightroom preserve the original file untouched while giving the external editor a lossless, fully rendered version to work on.
TIFF is commonly used because it’s a widely supported lossless format. So the main reason is not just history tracking—it’s that Lightroom’s whole workflow is built around keeping the RAW original unchanged and passing a rendered copy to programs that need pixel-based editing.
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