todd_shaner_6660895's profile



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Fri, Mar 15, 2019 3:46 PM

Lightroom Classic Full-Size Lossy DNG Workflow Suggestion

(This is a companion to a similar post specifically for
Lightroom CC–Please do not merge.)

This proposal provides suggested changes to the Lightroom Classic Smart Previews workflow to allow using full-size lossy DNG files for 1) Offline editing, 2) Lightroom CC Sync, and 3) archive of the original image files. These suggestions are applicable and beneficial across the entire Lightroom Classic and CC Desktop, Web, and Mobile ecosystem. Full-size lossy DNG files are useful for both local and Cloud image editing, reduce the required local and Cloud storage space, and speedup file transfers without sacrificing image quality.

As higher megapixel cameras become more common the benefits of using lossy DNGs are even greater.


Off-Line Editing Workflow

The current Smart Preview workflow allows storing the original full-size image files on an external drive and keeping the smaller Smart Previews files on the internal system drive. When the external drive is disconnected for field or home office use Smart Previews allow review and editing of the original raw files. The smaller Smart Previews work well for most purposes, but the usable output file size is limited to 2560 pixel long edge until the external drive can be reconnected.

I’ve done considerable testing of raw, JPEG, TIFF, Panorama DNG, and HDR DNG files converted to full-size lossy DNG export files for off-line editing with no issues.


- Full-Size Review,Editing, and Export when the original files are not accessible (i.e. external drive disconnected).

- Reduced File Size of approximately 1/4 to1/6 of the original file size and near equal to a 90 Quality JPEG file size. The smaller lossy DNG file requires 75% to 85% less storage capacity and by virtue of file size reduction both local and Web based file transfer speed are increased by 400% to 600%.

- Quality Retention is very good with no“visible” quality difference observed between the original and the lossy DNG files I examined. Since Develop edits are not applied to the lossy DNG image file it performs the same as a normal DNG file with the majority of subjects and edits. More at the below link:

Certain image files(high ISO, underexposed) when applied with extreme settings may exhibit differences, but they should be the exception. The user then has the option to “back-off”some settings or wait until they have access to the original files on the external drive.

Optional Archive Workflow

Provide an automated archive function for image files that have been processed with no intention of further editing. Many high-volume commercial photographers export the original raw files to JPEG copies after completion of a client project and then delete the raw files. A better option is to create a Lightroom archiving routine that demotes the raw file toa full-size lossy DNG file copy as follows.

1) Replace the original raw file with a full size lossy DNG file including all metadata(keywords, develop settings, etc.) for secondary backup purposes. Offer an option to relocate the original raw file to a different drive location or simply to delete it. Associate the new lossy DNG files with any relocated original files, Lightroom Collections, and Publish Services.

2) Since these are archived images it makes sense to delete 1:1 Previews and Smart Previews keeping just a Standard Sized Preview for review purposes to help reduce the size of the catalog folder.

3) Provide a file type tag similar to what is currently used with Smart Previews to identify these as ‘Archive’ image files.

Adobe Administrator


10.9K Messages


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3 y ago

Thanks for the posts, Todd!