Lossy DNG vs. non-lossy DNG in Lightroom Classic

I think it depends on how much you value the images and how strong of an edit you migh do. Lossy dng can break down if you heavily edit your images in for example lifting shadows significantly etc. If you don't foresee ever having to do that, I guess it can be useful to do this. I personally would never ever do this. Not even for the 20 images of the same situation that I don't end up using. Disk space is cheap, even if you consider the multiple redundant backups you're supposed to make.

It doesn’t have to be an all-or-nothing decision. You might not want to use Lossy DNG for any 5-star keepers, like your life’s best work, or images you will want to exhibit as large prints. For those few images, you probably want to keep every bit of quality they have, and leave them in their original format.

But, for example, if your business is doing photo shoots, after the best one or 20 images are published, if you or some policy decides that the other 357 files that did not make the cut will not be deleted outright, Lossy DNG can save a lot of space keeping those in the archive “just in case,” even though chances are they will never be used. Lossy DNG can retain enough quality for a decent 8 x 10 inch print at least.

Similarly, Lossy DNG could be a reasonable choice to save space storing the thousands of family/personal photos that just aren’t that important or are low quality to start with. If anyone needs a copy for web or print, Lossy DNG would have more than enough quality for casual sharing.

Lossy DNG doesn’t save much storage space if you use it for a few images, only if you convert large numbers of them. But because I want the best images to stay in their original format, the only reason I haven’t actually used Lossy DNG is that storage has been cheap enough that I haven’t yet found it worth the time to go through all those folders and mark the images that should be converted.

I often convert large Photo Merge to Panorama and HDR DNG files to lossy DNGs. For some images I also save the raw files, but this still provides a large reduction in required disk space.

"In the past I converted all CR2 files in DNG (non-lossy), but now I am wondering if I should use lossy DNG"

Why do you feel you need to convert to DNG? Personally, I don't feel it's less secure long term than DNG. If I did, I'd likely save as TIFF since I feel that has more uptake in the industry than DNG.

The cost of storage has come down significantly, so I prefer to ensure all data is intact. However, if you do not see any difference, you find that lossy is a good option for saving space.

warmly/j

The problem with lossy formats is that it's a one way street. You can't go back.

The reason for not using lossy DNG is very simple: I want all the data the sensor recorded. That ends the discussion as far as I'm concerned. Disk space is an unrelated issue that is dealt with as the need arises.

I suppose it comes down to what the images are used for.