DigitalPro Shooter Volume 2, Issue 28, September 29, 2004
Welcome to DPS 2-28: Finally there is a standard for Raw files. This week Adobe introduced it's Digital Negative Specification (DNG). In this issue we'll tell you all about it and provide some thoughts on how it will evolve and what problems it may solve for you. We'll also update you on the latest in laptop displays. |
The worst part of shooting Raw is that there is no documentation for Raw file formats and that they vary from vendor to vendor and even from camera to camera. There are literally dozens of different Raw file formats out there, some of which have already been abandoned by their inventors. The goal of preserving the raw data captured by your camera sensor for posterity has been elusive.
Wondering if shooting in the
Raw is right for you? |
Just as importantly, on a day to day basis shooters have had to deal with quirky Raw file converters from their camera vendors or risk incompatibility by using third party converters which rely on reverse engineering the image formats. Even image recovery programs have suffered as they have had to struggle to recover image data from obscure and sometimes even encrypted raw file formats.
Finally, Adobe has stepped forward to do something about it. They have introduced the Digital Negative Specification (DNG) along with support for it in Photoshop and a free converter.
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Frankly, there isn't any real secret to the raw image data
provided by most current D-SLRs. They almost all record 12-bits per
sample with a linear response curve as seen through a Bayer array.
However, even finding that simple data has been hard as vendors have
stashed it in various places in the file, often compressed or
encrypted in an undocumented or deliberately hidden way.
But the trick is in the interpretation of that data. Every sensor has a different response to light and every scene was recorded under different conditions. |
Camera vendors have taken even more care to hide this image rendering meta-data. It includes some fairly simple data such as the user setting for White Balance to more sophisticated information such as the sensor's black and white levels. Then there are the color matrices that should be used to convert the image to a known colorspace, tone curves and other camera specific data. In some cases this information is hidden to provide an advantage for the vendor's own raw processing software. In other cases it is probably just lack of resources to document and support the format.
Just to give you a sample, Canon has various recorded Raw files as .CRW, .TIF (but with its own data layout) and most recently .CR2. Nikon has always used .NEF, but changes portions of the file with each camera so that Nikon View and Nikon Capture often need to be re-released before they can even display an image from a new camera. Kodak has had a variety of versions of its formats, and then there are other formats from Fuji, Olympus and other camera vendors who support raw image capture.
Want to learn to get the most out of Adobe Camera Raw in Photoshop
CS? |
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Adobe's DNG proposes a standard way to encode much of this information, including White Balance, Black Level, White Level, Color Matrices, anti-alias filter strength, color noise and even light falloff. This would be a huge enabler of tools supporting Raw images. Viewing and processing Raw images could become as simple and straightforward as processing TIFFs or JPEGs is today. Camera vendors are still allowed to have proprietary rendering "hints" or other private meta-data stored in the file, but the basic data that is needed to accurately view and process the image is supposed to be available and stored in a standard location. |
The best news about DNG is that it is a very practical extension to the widely used TIFF format, also owned by Adobe. There is nothing in the format that would keep it from being used in a camera and nothing that would make it too hard to implement. However there are three stumbling blocks that DNG will need to overcome: First, industries are always skeptical about standards invented, owned and promoted by a single company. In particular, the industry will be watching not just for what Canon, Nikon and the other camera vendors do, but whether Microsoft decides to weigh in on the issue. An endorsement from Apple, which seems likely, would be a big help but won't make the standard a slam-dunk. Second, camera vendors will have to decide they are willing to implement a standard format in their cameras. A combination of pressure from photographers and increasing difficulty in keeping up with their own array of proprietary formats will be the eventual reason they move to a standard. But that move will take work and time and certainly impact product schedules in an industry which is already moving as fast as it can so the camera vendors will have to decide it is worth it to take that hit. Third, other software vendors will need to support the format. This seems very likely since it is not that different from TIFF and Adobe has clearly documented the additional tags. Plus, it is much easier to support one new documented format than to keep up with dozens of undocumented camera formats.
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Some of the features of DNG are very clever and
should help to ease digital workflows for those using it. For
starters, DNG separates the data used to characterize a camera model
from the data for a specific camera. This means you can take
advantage of per-model camera "profiles" but still customize (or
your vendor can customize) your images for your exact camera.
DNG also allows for both a true encoding of the sensor data or a pre-processed version that has been converted to linear. This will cause a little confusion as users decide how to choose, but the linear mode allows the photographer to keep the data in an easier to view form in case they don't have a viewer that knows how to interpret the raw sensor data from their particular model camera. |
Thoughtfully Adobe has provided a free simple batch converter to DNG for most current raw file formats. It is quite fast--since of course it doesn't actually render the images it just re-organizes them a little, so running it isn't too much extra overhead. However, it also doesn't generate large preview images, so you're still stuck with just a Raw image when you're finished. The capability to generate previews as it works will certainly be a popular upgrade request.
Adobe has also released Adobe Camera Raw 2.3, an update to the PS CS plug-in that adds support for popular cameras such as the Canon S60 and for DNG.
One obvious use of DNG is for archiving. If you make it a habit to save a copy of your Raw files to CD or DVD for your archives, then a DNG version is an attractive addition. Of course if you save DNG instead of .NEF or .CR2 or .RAF then you're betting on Adobe being the longer term player in this market--or at least that DNG will pick up enough steam that other vendors will be around to support it over time. Personally I think that is a good bet, at least compared to the odds that a particular camera vendor will still be supporting their format of today in 20 years. So in my opinion it is a risk tradeoff worth making if you're committed to using Adobe tools. And if the format picks up steam then it might be the right decision for everyone creating archives.
For your day to day workflow the obvious issue is support for the format. Without a converter that generates large previews, all your image browsing and management software will need to directly support DNG before you can switch to it. Since the format is straightforward and well documented I'm optimistic that this can happen within a year--at least for products currently in production.
Then there is the downside. If you currently like your camera vendor's software for processing your raw files, it of course will not work with DNG today. And my guess is that the camera vendors will be slow to add support, since they have so much invested in their current formats. Users of camera vendor software will probably need to sit on the sidelines for awhile as far as using DNG, and see how things play out with their specific manufacturer.
So far the photographers on our forums are taking a wait and see attitude. Join us and share your thoughts on DNG and how it might affect your digital workflow.
Given the huge need for this solution its future looks very promising. Barring some unified consortium trying to implement a different competing standard, it should only be a matter of time before DNG takes hold. Expect support from most third party software makers within a year, from camera vendors' software within two years, and cameras which can shoot native DNG as early as a year from now but mostly emerging 2-5 years out.
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Resources:You can Read about it You can Download the Photoshop CS Update to Camera Raw You can download the Adobe DNG Converter for Macintosh You can download the Adobe DNG Converter for Windows |
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| DigitalPro3 has been updated with initial support for DNG. Version 3.1 (beta)
will display thumbnails from DNG images, support JPEG+Raw file
grouping for Raw DNG images, allow batch processing of DNG images
with Photoshop ACR 2.3 and open DNG images in Photoshop (once you
update your Photoshop with ACR 2.3). A future update will fully
support viewing high-resolution DNG images. See why DigitalPro3 has already won the 2004
American Photo Editors' Choice Award!
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We've finalized dates for our Alaska Grizzly Bear & Puffin photo safari for 2005. It'll be from July 17th-24th. We've already got three slots filled out of our maximum of five, so it's not to early to sign up.
Our Monterey Bay Photo Safari for October 24th-28th, 2004 is SOLD OUT. Thanks for the great response.
I'll be the guest speaker at the Bay Area Bird Photographers on November 3rd in Palo Alto, with lots of slides of the Cook Inlet area in Alaska, featuring Grizzlies, Moose, Eagle, Puffins and more.
Read David's article on Histograms in the October 19th issue of PC Magazine.
