RAW vs. DNG

Everyone who wants to get the most out of his camera has to decide some day which file format to use. JPEG is standard for most (all?) digital cameras. Many cameras offer the possibility to store the raw sensor data onto the memory card instead or together with JPEG format. To create a visible image of this raw data you need a program called "raw converter". You can use the program of the manufacturer of your camera or you have to choose one of the many raw converters on the market.

There exist for example Adobe Raw Converter (ACR), Adobe Lightroom, Raw Therapee (Open Source), After Shot (Corel), Capture One (Phase One), DXo Optics, ....
If you only create JPEGs, you immediately have a picture to see, print, post on the internet or whatelse you want to do. To get a perfect JPEG, you need to use your camera the same way we did with film reels. There where very limited (negatives) or no (diapositives) possibilities to correct wrong exposure or usage of daylight film with candle light.
The raw file instead gives you the possibilities to change white balance without quality impact and lets you correct exposure and colour in a wider range as it is possible with JPEG files.

RAW is not RAW

Unfortunately manufacturers of cameras do not use all the same file format for their sensor data. Therefore you cannot use for example Sony's raw converter for pictures of a Canon camera. The answer of Adobe to this situation was to create a standardized raw format, called DNG (digital negative) and has been pushed on the market.

These are the advantages of DNG (as Adobe says)

For photographers:

DNG format helps promote archival confidence, since digital imaging software solutions will be able to open raw files more easily in the future.
A single raw processing solution enables a more efficient workflow when handling raw files from multiple camera models and manufacturers.
A publicly documented and readily available specification can be easily adopted by camera manufacturers and updated to accommodate technology changes.

For hardware and software manufacturers:

DNG removes a potential barrier to new camera adoption, since raw files from new models will be immediately supported by Photoshop and other applications.
The DNG format allows R&D savings by reducing the need to develop new formats and by simplifying camera testing.
A common format allows greater control over the quality of conversions by third-party applications.
The specification allows the addition of private metadata to DNG files, enabling differentiation.

DNG in practice

First of all - the following is my personal opinion built by my personal experiences.
When I noticed the advantages of RAW over JPEG in my early digital camera days, I changed my "workflow" to RAW. And when Adobe came up with DNG they successfully frightened me that some day I may lose all the advantages of RAW files because there does not exist any standard. I began to convert my RAW files into DNG files. Because of the big amount of data I have deleted my original RAWs and was happy that DNG was smaller than my MRW-files (of my Konika Minolta camera). I felt well with my future-proof DNG files.
My raw converter program in these times was "RawShooter" from Pixmantec. After some time Pixmantec has sold their product to Adobe and support stopped for a while. When Lightroom V1.0 has been released I was very disappointed about workflow and speed of the new product. Therefore I searched an alternative and found "Bibble" from Bibble Labs. This program was at lightning speed in comparison to Lightroom and offered a very interesting possibility to extend the functions by plugins.

DNG is no guaranty for future

First thing that I noticed was, that I could not open all my DNG files!! Soon I noticed that the only program on the market that supports the DNG files of my camera (and I could pay) was Lightroom.
Therefore I was forced to keep my aging RawShooter together with my new Bibble raw converter.
In my opinion Adobe raised wrong expectations.
(Later Bibble has sold their product to Corel and in my opinion the product now is "going down" there. Meanwhile Lightroom is a good raw converter with a lot of functions but I still do not like very much the workflow. Therefore my preferred raw converter now is Capture One. But this is another story)

DNG is not DNG

Bibble supported the DNG format of some cameras but not the DNG files of my camera. Shouldn't be DNG a standard format!? How can this happen?
The answer of Bibble's developers to that question was, that whenever a new camera comes on the market, the software must be adapted to their proprietary data - even if it is in DNG format. So what is DNG? It seems to be only a well defined container format but the sensor data of the camera within this container still is proprietary(?).
You can compare this situation with an envelope of a letter which is written in standardized english. I can read who has sent me the letter. But when I open the envelop and the letter is written in Japanese I still cannot understand regardless of the standard! I first must learn Japanese to understand.

DNG - standard or not?

1st experiment

I created a DNG file with Lightroom V6 and tried to open it with Lightroom V1.3. It is not possible - Why?
Photoshop CS3 also cannot open this file. It appears an error message.

Then I created a DNG file with Capture One - I can open this file with Lightroom V1.3 but it is unusable because of a heavy green colour cast.
Isn't DNG a standard?
When you are looking deeper into Lightroom V6, then you will notice that there exist different options to create DNG files. What do newer versions have better than older? Do they produce a better image quality? Do they contain more information? If yes - so I am loosing something if I convert a original RAW file into DNG!
If no - I don't understand the sense to create a new version which is not compatible older versions.
Why do there exist different versions if DNG is "future proof"?
-> I do not have confidence in DNG!

2nd experiment

I created two DNG files of a RAW image file - one with Lightroom 6 and one with Capture One 8. Then I opened the DNG file made by Lightroom with Capture One and the DNG file made by Capture One with Lightroom. What I saw where two completely different images. The default white balance was totally unusable!
For me another reason why not to convert my original RAW files into DNG.

If you study the compatibility tables of different raw converters, you will notice that many programs only support DNG format if the camera itself creates DNG files. Converted DNG files often will not be supported.

No longer sidecar files with DNG

Another advantage of using DNG files is (according to the fans of DNG), that Adobe Raw Converter or Lightroom no longer create sidecar files (XMP files) where your develop settings will be stored. You only need to copy a DNG file to another computer, open it with Lightroom and will see the same settings you had before. You no longer have to struggle with forgotten sidecar files. This may be a help if you are moving and/or copying your files a lot.
But! My understanding of "digital negative" is another. I do not trust in nothing that changes my RAW files. A manipulated original no longer is an original. The most critical moment for data is, when it is written to disk. To prevent the loss of data you will need a copy. To be sure that you always have a way back to the start, you will need the very first, still untouched version of DNG. And you will need also a copy of the modified DNG file (in case your hard disk fails).
Working with RAW files I only need one copy of the original file (to prevent hardware failures) and a copy of the very small sidecar file. There is no risk that a buggy software will garble my RAW file. Raw converters only read, never write to my RAW files. To have a RAW file seems to me a much better confirmation to be the owner of an image than to have only a modified DNG file.
So - if you are also thinking about backup, you will not safe disk space if you are using DNG files unless you are running risk.

Conclusion

To come back to the arguments of Adobe to benefit DNG format ...

For me there does not exist the future safety because there is no guaranty that DNG files will be supported by other software developers than Adobe. It is much more probable that you can find software that supports your original RAW files. And do you really believe that Adobe some day will not support the original RAW files anymore?

My workflow is the same for all RAW files of all different cameras. If you are using special camera colour profiles you nevertheless will need to make differences by camera type. I cannot find any reason why the workflow should be different if I am working with .arw, .cr2, .nef or .dng files
I am not able to decide if manufacturers of cameras can benefit from the usage of DNG format. If they think, that it is better - OK. So my future RAW files will end with the suffix .dng
When you buy a new camera you always have to wait until your raw converter will support the new camera type. Maybe that Adobe is very fast in implementing the new camera type in their software but you have to wait. Adobe DNG converter also does not support all cameras of the future - you have to wait. Same thing for original RAW files - you have to wait.
Why does DNG reduce costs? A new generation of Canon D5 will probably also create cr2 files with very similar file format as the actual model has. There will be new versions of cr2 files but there already exist different versions of DNG files and also will be developed newer versions of it.
I have no idea what's about control over quality - it's not relevant for my daily work. If manufacturers think DNG is better, no problem - go on.

For me personally I have not found any advantage to use DNG files. Quite the contrary - I had big troubles because of converting my RAW files into DNG files because I was bound to stay with my old raw converter. I do not expect that software developers will support DNG files of the first generation of digital cameras longer than their RAW files. DNG is (still?) not very common. It seems to be only supported with guaranty by Adobe. I'll keep my RAW files and save time not converting to DNG.
I am working with RAW files because they will not be written by raw converters and therefore backup is easier to handle and needs less space.
If DNG will become a standard by manufacturers - no problem. That's OK.