DNG vs. .CR2 or ...

[Ian Cassell]

I'm sure this has been discussed before, but can't find it in a search and I would appreciate a link (or a fresh answer).

With my new camera (7D2) and a new year coming, I'm rethinking my processing workflow. I've been considering switching from saving all my .CR2 RAW data to converting to .dng and saving those instead. I'd appreciate thoughts on advantages/disadvantages of the switch or other suggestions. What do you do?

Thanks in advance!

[Diane Miller]

Enthusiasm for the idea behind DNG, which is platform independence, has simmered down quite a bit as far as I can tell. If the doomsday comes when Canon's raw formats are no longer supported, I can't imagine that there won't be time to convert old images.

I set LR to save metadata (develop settings and ratings except the black and white flags) in sidecar files, as a double-up with the Catalog (it will be in both in that case). With DNG files the metadata is written in the header of the file itself, and the whole file has to be re-written to store metadata changes, which isn't very practical. A sidecar file (.xmp) is just a tiny text file that is written almost instantly. So with DNG you are relying on the Catalog to store metadata such as develop settings and ratings.

It's rare for a Catalog to be corrupted, and it can usually be recovered IF it has been backed up recently. I'm currently trying to help someone who uses DNG and relies very heavily on Collections for organization. About a year ago his iMac got slow so he got a new one and took his backup disks (apparently a complete set) to someone at an Apple store to migrate everything over to the new machine. Everything seemed fine until some while later he discovered some valued Collections were missing. He had only been backing up the Catalog every few months and now he has a big problem over which he is extremely distraught. He has a huge collection of many years of excellent images. The images appear to be there (in external drives) but a lot of the organization and develop settings appears to be lost.

So a note of caution -- if you rely on the Catalog, back it up OFTEN. Old backups do take up space, so I go in and delete old ones every so often, keeping those from a time period when I'm pretty sure everything was OK. And I rely on Keywords and folder structure for fundamental organization. Keywords are stored in the sidecar files and accessible to ACR, along with the other settings. I mostly use Collections (which are exclusive to LR, stored in its Catalog) for more temporary organization, such as images I might want to post here, and the like.

[Ian Cassell]

Thanks for your thoughtful response, Diane. For years I've stored my RAWs as .cr2 files, but every once in a while I get some crazy notion that I should be doing things differently. I too think that there would be time to convert if Canon changed, but another argument I've seen is that .dng avoids the .xmp sidecar and takes up less space. You seem to see that avoidance of .xmp as a negative and some see it as a positive.

The thought of converting years of .cr2 files to .dng doesn't thrill me, so I'll probably maintain the status quo unless I see good arguments to the contrary.

[arash_hazeghi]

If you convert your CR2 files to DNG you will permanently lose the Canon encrypted header section of the file that contains vital information. This information is used by the DLO module to correct for many aberrations. You will permanently lose the ability to use Canon software for converting and correcting your CR2 files. Other RAW converters are also not compatible with DNG.

it is probably the worst thing you can do to your CR2 files short of deleting them.

[Ian Cassell]

Thanks, Arash. No one seems to mention this. I'll keep the CR2 files.

[Juan Carlos Vindas]

CR2 files for me! not changing is smart!

[Daniel Cadieux]

Yep, all my "keeper images" raw files are saved and backed up. I cannot fathom the thought of losing them or permanently switching to another format.

[Miguel Palaviccini]

I used to convert to DNG. Mainly bc that was the thing to do when I started shooting. File sizes were smaller and the sidecar file was embedded. I thought it was the way to go for sure ...

... and then I tried to submit a photograph to a contest and noticed that most don't accept dng files (I assume its bc you can edit a raw, then convert to dng). I would also lose the ability to use DPP.

All in all, I don't see the benefit to DNG

[Diane Miller]

The reason would be that a DNG is a raw file. They want a processed file with your interpretation of all those parameters that you can control.

[Diane Miller]

That would be like entering a B/W film photo contest and submitting a negative.