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Old Apr 3, 2010, 8:34 AM   #1
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Default RAW vs DNG, or RAW & DNG?

Relatively new to digital (long time film user) and getting a bit overwhelmed by all the various file formats.

Anyway, watched a video tutorial this week (Better Digital Photography) about processing RAW files (or NEF in my case) in Elements.

I knew about RAW, NEF, TIFF, JPEG, GIF, but now I've been thrown a new one; DNG!

Am I right in thinking this is instead of RAW (as opposed to as well as, like TIFF)?
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Old Apr 3, 2010, 9:31 AM   #2
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DNG is basically a different way to store your raw files. You can read more about it here:


The main idea was to come up with an industry standard raw format. But, it really hasn't been embraced by most the major camera manufacturers, and you'll find in most cases, that their raw converters will not support anything other than the proprietary formats produced by a given camera model.

Now, a few manufacturers do offer .dng as their default raw format if desired. Pentax is one of them. But, for the most part, if you want to use the camera manufacturers' raw converters, you'll need to stick with their original format.

You'll find people for and against DNG. Here is what David Coffin (the author of dcraw.c) had to say about DNG in December 2004 when I asked him about what he thought about DNG then (and he said that I could quote him):

Dave Coffin wrote:
I think Adobe's DNG idea is well-intentioned, but suffers from two serious flaws:

First, why would camera makers want to change their raw formats? Compatibility leads to commoditization, and that leads to competition based on price alone. Great for consumers, terrible for producers.

Second, this format cannot anticipate innovations that haven't happened yet. When new sensors appear, the standard must be updated, along with the software that implements it.

There is only one way to guarantee that a digital archive will be readable in fifty years. For any non-text files, it must include decoding software as human-readable source code. If the decoder is written in a language other than C, it would be prudent to include an interpreter for that language, written in C.

Dcraw already fills this role. When the first DNG camera is available, dcraw.c will support it as one more raw format among many.
By the way, dcraw.c now supports DNG. Here is more recent quote from David Coffin (March 9, 2005). He's "warmed up" to .dng a bit since it was first released.

Dave Coffin wrote:
After four months of work, dcraw 7.00 is available for download at http://cybercom.net/~dcoffin/dcraw/

It's a major rewrite:

* Not only is Adobe DNG now supported, the entire codepath has been redesigned for it. Adobe's XYZ->CAM matrices allow color science to replace black magic, whether decoding DNG or the original raw files.

* The Foveon-related code has been completely rewritten to give realistic colors under all light sources. The license has changed. The new Foveon code is under the GPL license, so authors of closed-source applications may need to pay me to use it. The rest is under my old free-for-all license. See dcraw.c for details.

My future plans are:
* Adding support for SMaL-based thin cameras ( http://www.smalcamera.com ). Currently these cameras are completely useless without Windows.

* Improving camera white balance support, first for Canon, then Nikon, and maybe others.

Dave Coffin 3/9/2005
Personally, I keep the original raw files, along with a copy of dcraw.c, just in case support for a camera ever ends.

I also keep copies of popular open source programs that can read metadata from raw files (DigiKam and others), so that I know where to find maker notes, etc. in the raw files should the need ever arise (without the byte offsets changing by using a container like DNG as a medium, even though it supports private data).

DNG is probably a safe bet (since dcraw.c can convert it to usable images, as can a number of other open source programs that use some or all of his code) for most uses if all else fails. But, I'd rather have the added security of support from any programs designed to read the metadata at specific byte offsets in the original raw files from the camera manufacturer, too.

I never overwrite my originals, raw or jpeg. I look at the originals as being the best you can start with, and I don't want to lose them or take risks by trying to archive them in a different format.

dcraw.c will compile using an ANSI C compiler for just about any platform that has one (and that's just about any of them around that would be used as a desktop or server). It's not limited to AMD or Intel, Windows or Mac, etc. Almost any operating system has an ANSI C compiler available.

There is no platform specific code in it (so, no need for different versions for different operating systems). That's the beauty of keeping it ANSI Standard C. The compiler takes care of making the code platform specific.

dcraw.c supports more cameras than Adobe Camera raw, and some or all of David's code is used by a number of both free and commercial raw converters.

Raw converter developers can use David's code as a model, then add their own Graphical User Interface, enhanced alogrithms and features unique to their products, etc. Some use it for documentation of the formats if for nothing else. dcraw.c is ANSI Standard C, and it's free. So, David does the work, others take advantage of his good will.
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