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Wednesday, 14 May 2008

To DNG or not to DNG?

One of the great things about DSLRs is that you can shoot in RAW format. This is essentially a digital negative and allows you much more freedom in post processing and prevents image degradation. The problem with the RAW format is that everyone and their dog has their own proprietary type, and they keep changing it.

I was reading an excellent article about digital workflow at Pro Photo Life and the subject of data preservation came up. What good is properly archiving your RAW files, if in 10 years no software can handle them?

This naturally lead to the DNG format.

DNG is a "universal" RAW format for Cameras developed by Adobe. In fact they have recently submitted the format as an ISO standard (DNG submitted to the ISO). DNG has been around for a while now, and Adobe offers a free conversion tool (windows version, mac version) to convert your original RAW files. you can also do this in Adobe Lightroom with a few options:
  1. Convert to DNG
  2. Convert to DNG and embed original RAW file
The logical question is what is the file sizes of these different options compared to the original file? I decided to take a few sample RAW files from a recent shoot and test it out.

Here is the data:

File Size

Original
CR2
DNG DNG
+embeded RAW
11,977 10,362 22,024
12,295 10,678 22,727
11,572 10,131 21,437
11,204 10,012 20,952
13,763 11,526 25,063
12,500 10,498 22,677
11,409 9,500 20,575
11,300 9,792 20,845

Camera: Canon 1D Mark III

And the change:

Original
CR2
DNG DNG
+embeded RAW
100.0% 86.5% 183.9%
100.0% 86.8% 184.8%
100.0% 87.5% 185.2%
100.0% 89.4% 187.0%
100.0% 83.7% 182.1%
100.0% 84.0% 181.4%
100.0% 83.3% 180.3%
100.0% 86.7% 184.5%

A quick average reveals the DNG only format is about 86% the size of the original file and the DNG + RAW is about 184% the size. Is the DNG file just as good? I don't really know. I have used the format a bit and had no problems, but there still might be some data loss there. Of course for just under double the size, you can have both.

My question is this: Do you DNG? If not, why?

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posted by Neal at

5 Comments:

Blogger advman said...

So far I don't use DNG. Probably I should, but the 18366 NEF files that I have at the moment scare me a little :)

Then there is Nikon's Capture NX. This is not just "the camera vendor's crappy RAW converter", this is a really useful application, and in some cases, when I am absolutely satisfied with colors and tones that came out of the camera, it is much easier to use Capture NX for conversion, and then do e.g. some cloning in Photoshop.

Capture NX won't work on DNG though. Thus it would be more like converting to DNG and keeping NEF as a separate file. Hmm ... doubles disk space :)

But probably I'll do exactly that in a year or two. Hard drive capacities grow faster than my space needs, thus I think as soon as 4 TB drives are available (maybe two years), disk space will still be a topic, but not for photography any more. HD video, yes, but not photography. Even now, with 1 TB reserved for images only, I think I almost could do it.

But, wait, maybe acceptance of DNG by the ISO will change the camera manufacturer's attitudes. I think this could really be the point where we standardize on DNG. Basically it takes one of the big two, Canon or Nikon, to move, and then the other won't be able to hold back.

No, the more I think of it, the more it gets clear that I'll wait a couple of years. And why not? The only reason to change would be long-term safety. Nikon going out of business? I can't imagine. Nikon not supporting NEF any more? They'd be utterly stupid. THIS would drive them out of business :)

Still, as a long-term strategy it's a good idea, but I'll tackle it in a few years.

14 May 2008 22:19:00 GMT+01:00  
Blogger Neal said...

@ advman

Your rationale does seem sound, and certainly converting to DNG in a few years won't create software compatibility issues.

I would like to see the major camera makers start using DNG (or some other format) in their cameras like jpgs. Only time will tell if this happens, but I suspect that they will resist.

15 May 2008 12:13:00 GMT+01:00  
Blogger Jim said...

This is great! Thanks for the info, I'll link back from prophotolife by my next tech article (Tuesday). It would be great to see this conversation continue.

I did download the DNG converter a few years back and converted some Fuji S2 files (Fuji never had the greatest software support). At the time I was attending seminars and it was being pushed upon us that super-great info was included in the camera makers' proprietary formats. As a result, I never fully explored DNG.

Now my studio is part of a chain of technological obsolescence. Any time camera, computer or software changes we have to replace the entire chain, it feels like.

15 May 2008 12:52:00 GMT+01:00  
Blogger Zara said...

I'm sticking with native CR2 (Canon) files over DNG, at least in the short term. I'm a bit put off by the fact that post-processing metadata reside in the DNG file itself, rather than in an XMP sidecar, as they do for the native RAW formats.

This may be just a holdover from my film days and the notion of the inviolable negative, but I do like my RAW files to be essentially read-only. And the corruption problems that caused Adobe to "recall" the Lightroom 1.4 upgrade really added to my concern on this point.

16 May 2008 03:10:00 GMT+01:00  
OpenID originalmoose said...

Ok, so I'm no photography techie, and currently haven't had the opportunity to take any classes in it. I tried shooting in RAW once, but couldn't do anything with it on my computer and had to convert to jpgs to be able to edit them. My manual (I have a Canon digitial Rebel SLR) even says that it's not a recognised file type by most software programs. Is there something you can recommend as a user friendly program for me to learn and experiment with so I can start getting the most out of my camera, and see what all the hype is about over RAW? Thanks!

15 December 2008 22:26:00 GMT  

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