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Lossy DNG vs Original Camera RAW

Storage has long been a problem. Despite Moore’s Law, I seem to keep filling larger cheaper drives. Ok, so it’s a first world problem, I admit it! At some point in the past, I was converting all my raw files to RAW. The appeal then was that the DNG files promised to be more universal than the RAW files produced by various camera manufacturers.



Comparisons of RAW and Lossy DNG with Photoshop, Affinity Photo, and Capture One at 1:1



ARW file processed in Photoshop with auto settings (left), Lossy DNG processed in Photoshop with auto settings (center), Lossy DNG processed in Capture One with auto settings (right) all at 1:1 pixels.

Unfortunately, Adobe seems to be a less and less friendly company. I’ve been doing the right thing for decades and paying for their software. But they seem to be trying to make everything much more difficult with licensing and not sharing the details of their DNG format with other image editing competitors.
None-the-less We’re stuck with Adobe for a lot of things. I tried and liked Capture One. But C1 is only a substitute for Lightroom. Somehow at times you’ll need to edit photos with Photoshop or similar. Serif’s Affinity Photo is pretty capable for what it is, but not good for converting RAW files.
So here I am using Lightroom. At times I’ve been converting RAW files to Lossy DNG’s for backups. And frankly I think They’re usually good enough that I don’t need the original RAW files. So I thought I might do a few side by side comparisons for myself- and then to share with the world (or at least you who reads this!)
Presently I’m looking at a backlog of old photos from a trip in 2017. I already have created the Lossy DNG’s and thought these images would be good for this test.
First obvious question, how much do you save?
I choose a sample photo because there is variation from image to image. The image I choose reads as:
Lossy DNG 12.5mb
Camera JPG 13mb
Camera RAW (lossy compression Sony ARW) 42.5

I must say I find this to be a surprise! The lossy DNG is slightly smaller than the Camera JPG.
What you can do with a Lossy DNG that you can’t with a JPG?
Turn on or off Lens Corrections
Recover blown out details if they were in the RAW file
Recover lost shadows if they were in the RAW file
As best as I can tell, pretty much all the benefits of the Camera Raw file apply

Some other differences between the function of Sony’s ARW raw file and the lossy DNG:
DNG’s don’t use a “sidecar” to store Metadata. That could be an advantage in some ways, like the info will always follow the file when transfered. But it adds to the processing time when editing Metadata since writing the info is added to a 10-20mb file, rather than a 2k “sidecar”.

Since Adobe no longer plays nice with (anything really,) editing these lossy DNG’s could be a challenge with a competing software program. But my testing in Capture One seemed to go without a hitch. Affinity Photo had pretty poor results with both file types.

How does this work? Honestly I have no idea! But there seem to be some compelling reasons to switch to a workflow.
Feel free to download all the test files for your own personal use and testing here.
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