# Lossless DNG compression in LR?



## erudolph (Nov 25, 2019)

I've recently started shooting with a Leica camera that has a 47mp sensor.  Its files are about 84mb DNGs.   I've read that using the "Update DNG and Metadata"  command in Lightroom's Metadata pulldown menu will compress the files to about half their original size.  I did a quick test by duplicating a file, compressing one copy, leaving the other uncompressed, stacking the two copies in Photoshop layers and selecting Difference as the blend mode.  The result was a black frame which encouraged me. 

My question:  is this compression scheme, i.e., using this command on camera original files, a safe practice?  Thanks for your insights and advice.


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## johnbeardy (Nov 25, 2019)

That "Update DNG and Metadata" is a lossless compression, and one shouldn't imagine that any file size decrease must be at the cost of image quality. The size and quality of the embedded previews are one variable, and more optimal storage of the same data also demands time and processing power which would be different in the camera from the desktop computer.


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## erudolph (Dec 4, 2019)

Is it possible to apply "Update DNG PReview & Metadata" as part of the import process, much as you'd apply a preset?


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## johnbeardy (Dec 4, 2019)

Maybe if you import using the Copy as DNG option. It may not be available when the file is already a DNG.


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