PhotoshopNews has an article on using a DNG Workflow <http://photoshopnews.com/2005/05/23/dng-workflow-part-i/>

Thanks, Jeff. You and Bruce have done us a big favour with your free stuff.

2 Points:

1. A comment on "The resulting DNG file will be the size of the converted DNG file plus the addition of the original proprietary Raw file combined". My observation is that it is a less than this, at least for my camera. I suspect that what happens is that the embedded original Raw gets (losslessy) compressed in the DNG more than cameras manage. Is this the case?

2. Futile to ask, I'm sure - but when will the Pentax proprietary metadata be copied across, if ever? (It isn't a stopper for me - I think I just lose the lens model, perhaps not much else. But, always nice to have these things).

#1, I'm not sure why that is. . .it could be that the embeded raw is recieving the benefit of additional compression. What format are your proprietary raws in? Pentax? Maybe Thomas can answer that.

#2, a question for Thomas. DNG Converter 3.1 is moving the private maker notes from the original raw file into the private areas of DNG safely for NEF & CR2 files-which means that in essence, nothing is lost even without embedding the original raw file. As for support for private maker notes migrated for Pentax, that's a Thomas question. I really couldn't guess.

The code change in ACR/DNG 3.1 that preserves private MakerNotes applies to all formats that store their private data using the Exif MakerNote format, which includes Pentax.

These MakerNotes are often byte order or offset dependent, so what I'm doing to preserve this data safely is repackaging it into the DNGPrivateData tag. This repackaging stores the source file's byte order and the original file offset to the MakerNote, along with the MakerNote data itself.

This allows an application that understands the MakerNote format for a particular camera to find the MakerNote data, along with the original byte order and file offset, and thus parse the MakerNote data correctly from the DNG file.

I'm working on writing up a brief technical note for party developers that documents the format Adobe is using to store this repackaged MakerNote data.

Jeff,

Also, I am to understand from your article that any proprietary metadata that exists in some RAW formats (i.e. non CR2 or NEF which you say have all their metadata copied over into the DNG) that can't yet get put in the DNG is also metadata that one never sees if using ACR in the first place anyway, right? It makes sense and seems ovious, but just checking. In other words, I'm not losing anything if I've been using ACR all along on my RAW files, by converting to DNG and not keeping the RAW file.

Also as a minor question, with ACR 3.1 I can now convert/save all my CR2 files as DNGs w/o using the converter app - I do it all from within ACR. The only thing I see that ACR can't do that the app can, is extract an embedded RAW from the DNG. Or can it? If so, the app is optional then.

Thomas, thanks for explaining this change in ACR/DNG3.1. Do you have any documentation about which camera manufacturers currently use the Exif MakerNote format, and are thus covered by ACR/DNG3.1?

It would be nice if there was a simple way to add a larger preview to the DNG file. A downside to moving from a CR2 to DNG workflow is that the large preview of the CR2 is lost. This is annoying if a product like Photo Mechanic is being used.

Regards,
Fergus

You can add full-size previews to DNG using either DNG Converter 3.1 or Camera Raw 3.1 by selecting that option in DNG Converter's Preferences or in the ACR 3.1 Save dialog.