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

+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:

+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 Links to this post