Converting JPEG to DNG

[dcthompson]

All,

I have read everything I can find on the subject of converting JPEG to DNG and I just want to confirm my findings.  As I understand it, there is really only one reason not to do the conversion at this point in time.  That reason being the increase in file size due to the way that a JPEG is currently stored in a DNG.  My questions :

1.  Am I correct in believing that this is the only stumbling block?
2.  Does anyone have a feel for when/if the specification and, more importantly, the DNG converter, will be updated so that there is no (or a minimal) size penalty?

I am currently migrating all legacy photographs to my DAM flow and plan to convert JPEG to DNG to allow for non-destructive editing, etc.  I am willing to take the hit on storage space if the change is not near (I don't want to hold off my legacy migration much longer) but if it is soon...

Thanks,

David C. Thompson

[icurate]

Hi David,
   I, too, am in the process of converting all my JPEGs to DNG.
1 - As far as I have found the only negative is file size.
2 - I wouldn't expect any changes to DNG as far as accomodating JPEGs.
      Since JPEG isn't a lossless, archival format it would go against part of the purpose of DNG.

I'm not saying I wouldn't welcome the change, I just don't see it happening.

Take care,
                Jeffrey

[Ken]

Something to consider as you ponder over the conversion process:

In this thread, http://thedambook.com/smf/index.php?topic=2523.0#msg14381 , Peter stated:

There's no particularly good solution for this at the moment.  I think making DNGs from the JPEGs will ultimately make the most sense.  But until the DNG spec gets slightly modified (and a corresponding capability get put into Lightroom), you take a pretty big hit on file size.

The DNG can contain the source image data, and the adjusted image, but the source JPEG gets converted to TIFF data in the DNG and therefore gets pretty big...

HTH,
Peter

Good luck,

--Ken

[peterkrogh]

David,
If you're willing to take the hit on file size, go ahead.
I would not expect to see a workable version of this in less than a year.
Peter

[dcthompson]

Peter,

Thanks for the timeline.  Do you have any thoughts on whether or not the new converter, when it does arrive, would be able to reprocess the existing DNGs to shrink them?  I am still looking at my options but would really like to get moving on the legacy JPEGs.  And, yes, I have come up for air from the "keywording nightmare" that I dove into.  By the way, I did end up using separate keywords.  The savings in entry time and overall flexibility is well worth the minimal number of "false positives" that I have been encountering.

Ken,

Thanks for the reply, I had read that thread (as well as numerous others) and am fully aware that there will be a huge hit in space requirements.  I was just trying to make sure that there were no other pitfalls.

Jeffrey,

Glad to hear that you haven't encountered any problems other than the increased file sizes.  As Peter knows from my previous thread on keywording, I tend to over think things (trying to get away from that habit, I think) and stop cold when I hit a glitch.  As a result, I hate to head down a path where there are unknowns (to me) that can be resolved (by others).

Again, thanks to all.

David

[peterkrogh]

David,
I think that a new DNG implementation that would shrink the file by using JPEG compression on the original could work in two ways.

#1 For files that are JPEG originals, it could pick up the original file and place it in the DNG.

#2 It could also offer the possibility of compressing the original regardless of the original format.

If #1 is the only option, then you would probably not get the advantage by reconverting these DNGs, since you would not have the original to work from. 

If #2 is the only option implemented, then you could recompress, but that might not be desirable, since it would toss out some limitied amount of data.

[dcthompson]

Peter,

Good points.  I guess I hadn't thought it through all the way (about the conversion).  Option #2 is off the table since I don't want to degrade the images any more than I have to.  Option #1 may be something to consider.  I could hold on to the originals (as one of several backups) until it became clear what Adobe was going to do.  Guess I will have to think it through some more.

Thanks,

David