Compress your native Pentax DNG photos AFTER import into Lightroom

I spent the last days cleaning up my photos and Lightroom catalogs. While importing/exporting and updating I noticed that the Pentax DNGs are uncompressed (around 17mb per file) and if I import them using the Lightroom “convert to DNG” command, they are compressed to about 9mb each.

However, using the existing “Convert Photos to DNG” command will not compress the existing DNGs in the library!

This is found under the “Library menu in Lightroom 3” and works great with Nikon or Canon Raw files. However, DNGs are ignored by this command.

You won’t have to re-import all photos to get the benefit of compression though.

There’s a solution which is not very obvious but worked very well for me:

Select the photos in your catalog and choose “Metadata -> Update DNG Previews & Metadata”

This will take the uncompressed DNGs and compress them, giving you between 10%-40% of space back!




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I've always been interested in all kinds of art because I felt the need to express myself in many different ways. I paint, draw, create 3D models, motion graphics & designs of all sorts, play guitar, love photography and whatever else is in between... I was born in Hungary and lived in Hungary, Germany, Australia and the UK for a number of years. I speak German, English and a little Hungarian (I'm working on improving that one again!).

2 thoughts on “Compress your native Pentax DNG photos AFTER import into Lightroom”

  1. When I import my photos to Lightroom I am having lightroom
    convert to DNG on import. Are you doing the same thing? I guess
    this concerns me if the DNG files being created on import are not
    already compressed. Hmm…

    1. Now, I’m doing it on import but I haven’t done that in the past. I simply copied the DNG files straight from my camera (without converting them because I thought that my camera already produced compressed DNGs – turns out that’s not the case with the Pentax K200D). If you have always converted on import you should be fine and not need to do this.

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