RAW Formats and Converters – Part 2: What about DNG?

Please read the First Part of this Series

DNG is a format created by Adobe to attempt to respond to the increasing complexity of RAW files, and their non-standardized formats. It makes sense that Adobe  would take a leading role in such a project, since Adobe’s software must open files from all types of cameras. A universal format for RAW files is an excellent idea: the RAW data from any camera could be brought into a standardized format, so that there will be no questions about the ability to read a given camera’s native files, and all files could then be treated in the same manner by any application that chooses to support DNG images.

It is even possible for camera manufacturers to use DNG as the native format which their cameras save files into, so that the RAW files coming out of your camera are already in DNG. Hasselblad, Pentax, and Leica are most notable for having explored this route, and RAW images created in some of their cameras are DNG files. Hasselblad reversed this decision after their H2D model, and moved to a proprietary format again starting with the H3D, to allow them to perform processing functions on their files before committing them to DNG.

But for all the simplicity and elegance of the concept of universalizing the format of RAW images, after nearly a decade of availability, DNG has not caught on. There are a number of reasons why. Not all camera manufacturer’s RAW formats and software play well with DNG; Nikon in particular is not DNG-friendly. If all camera manufacturers saw an advantage to porting their cameras to an in-camera DNG format, then the issue of RAW formats would soon disappear in the rearview mirror of the photo industry, and DNG would be the standard RAW format.

When RAW files are adjusted in a software application, those edits are not built into the RAW file. Instead they are saved into an additional file in the .XMP sidecar file format. Think of a little side car that can be attached to a motorcycle to hold more passengers; here the extra file’s passengers are whatever additional cropping and editing adjustments you have performed on the RAW image.

With DNG, the taboo of not changing the original file is gone; the original file has already been changed into a DNG file. Edits made to a DNG file are saved into the DNG file. This eliminates the sidecar file, and the possibility of moving the RAW image without bringing the sidecar file along, and losing all your edits in the process. But it also means your original file is being altered, so that there is not a single, unchanged copy of your image to fall back on. And the process of saving changes to a DNG image is slower than saving sidecar changes, since the entire image file must be rewritten when saving edits to a DNG. Minor considerations, perhaps, but they weigh on a photographer attempting to decide whether to move to a DNG workflow.

Unless your camera outputs DNG automatically, you need to go through extra steps to produce DNG files. This includes deciding whether to save your native RAW files, or to delete them once a DNG version has been created. Since the DNG format tends to be somewhat smaller than other RAW formats, there is a small space-saving possible by going the DNG route; however most photographers are very uncomfortable with deleting the RAW files. There is an option for imbedding the original RAW file into the DNG, but choosing this route means that DNG+RAW files will be nearly twice the size of standard RAW files; when those RAW files are already much larger than non-RAW formats.

Most photographers have not seen any problems with keeping their images in a RAW format library. Lightroom and other image management software do a good job of managing RAW files and the related XMP sidecar files with no additional complexity for the user. This means that simply downloading your RAW files to your image library, then previewing, sorting, deleting, rating, and editing them is a straightforward process that is not proving problematic, so changing that method to a workflow that involves DNG has not been seen as a necessary step.

DNG workflows have been available for nearly a decade, and have improved over that timeframe. But there has not been a universal acceptance by camera manufacturers of the DNG format in-camera, and the trade-off of advantages and disadvantages has not convinced the majority of photographers to move to a DNG workflow.

But there is one advantage that might push an increasing number of photographer to move to DNG: money. The next article in this series will look at the possibility of reducing the cost of ownership of photography software though using DNG and other workflows.

Credits: C. David Tobie, Copyright 2012.   Website: CDTobie.com   Return to Blog’s Main Page


4 responses to “RAW Formats and Converters – Part 2: What about DNG?

  1. My first camera capable of outputting raw files was the Olympus 5050(Z?). For some reason, Apple’s Aperture program has never supported raw files from the 5050. This is the very kind of situation I would have expected DNG to handle. Many of my 5050 images were converted to DNG format. Aperture still rejects them. It seems that conversion to DNG does not “universalize” an image file, or at least did not do so a few years ago.

    [Aperture’s problem with the old Olympus files seems very odd. It has no issues with Olympus E-PL1 files, and among the numerous raw converters I own, only Aperture slams the door on 5050 files.]

    1) Would DNG files from an early DNG-converter differ from those produced by the current converter?
    2) If they would differ in any meaningful way, is there a way of “updating” an old DNG file? [For some early images the ORF originals have been lost, but I have DNG versions as they came straight from an early Adobe DNG Converter program.]

    • This is the type of scenario that causes concern about DNG; which is ironic, because it is the very type of situation that DNG was created to avoid. Perhaps it might be possible to ‘launder” the problematic DNGs through another DNG-capable app, and see if Aperture could parse them once that had been done?

  2. Pingback: RAW Formats and Converters – Part 3: What Import Route? | CDTobie's Photo Blog

  3. Pingback: RAW Formats and Converters – Part 4: Which Apps to Update? | CDTobie's Photo Blog

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