The changing DNG spec

[pvonk]

I thought I'd give a heads up under this topic (from a similar thread in the Lightroom topic).

It seems Adobe's Bridge/ACR and the Lightroom beta can't read each other's edits of DNG files.  Adobe says it will be revising ACR along with DNG to make their apps read DNGs.  If interested keep an eye on the forum thread:

http://www.adobe.com/cfusion/webforums/forum/messageview.cfm?catid=589&threadid=1164124&enterthread=y

As I ask there, will third party apps have to upgrade each time Adobe changes the DNG specs?

(I hope I'm not being too much of an alarmist )

- Pierre

[peterkrogh]

Pierre,
It's a little hard to get your head around at first, but here goes:

First, while your issues are confusing, the problems that you fear here should not come to pass.

1. The DNG spec does not actually need to be changed to solve the issue, rather the code for LR and ACR needs to be integrated so that they can make use of the same instructions for adjusting the images.  This is a longstanding and known issue that relates to the status as beta software. 

2. The real missing piece right now is the embedded preview. This is the only way that applications other than the one that adjusted the file can see the image edits.  This is true for both DNG and proprietary RAW files. Expect this to be fixed.

3. DNG provides for versioning and backward compatibility.  DNGs you make today will still be readable in the future, and they will be able to be updated as new versions come available.  Most likely you will convert to the new version because you bring the image back through for a reason, such as wanting to take advantage of new adjustment tools, or of some future feature like multiple saved versions.  I don't think you will feel like you need to reconvert everything just because a new spec exists, rather, you will do the migration because there is some work you want to do to the files, and you will just happen to save as the newer DNG type.

Is this clear?  Any further concerns?
Peter

[pvonk]

Okay, Peter - let's see if I get this: 
1) A DNG file contains the original image information that was converted from RAW (or is still the RAW, but in a wrapper file??). 
2) Included in the DNG may be a preview.  The preview is used by apps that display the image (like IVMP). 
3) Also in the DNG are special commands that are placed there by an editing app like ACR or Lightroom to describe changes I may have made (like exposure or tint).

If this is right, then if I decide to further edit the picture in the future, I need to use an editing app that understands the commands (3) that were previously saved and that adds to them.  In addition, the preview (2) should be updated so other apps like IVMP can display the new version of the picture.

Is this the right overview?  If so, then I gather the problem with LR and ACR is that neither understands each other's edit commands.  Once Adobe fixes this, each app will be able to read the older commands when opening an older DNG and when saving further edits it will use the newer command format.  Right??  Somehow I think it's more than just the preview being unreadable.

- Pierre

[pvonk]

Well, here's Adobe's reply about DNG files and compatibility:

"DNG is an open format with versioning built in. Old DNGs -WILL- be able to be processed into Lightroom correctly when the Lightroom/Camera Raw pipeline is fixed. DNGs -FROM- Lightroom should be able to be processed by any DNG supported converter once the DNG spec is versioned. I believe we're already at DNG version 1.1.0 which incorporated the new functionality of Camera Raw 3.x which can even be read and processed by Camera Raw 2.4. And yes, other 3rd party apps that are DNG readers/writers will need to be rev'ed to compliant to new DNG spec versions. . .that's the nature of an open standard with versioning built in."

- Pierre

[evonzz]

I do not understand why if Adobe has created Bridge, ACR, LR, and the DNG, they cannot get this right from the beginning.

Rodney

[peterkrogh]

Which part don't you understand?  That capabilities of RAW file processors will continue to evolve?
Do you realize that TIFF has also evolved over time?
Peter