Camera Raw/DNG: Loss of information when converting raw to DNG

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Hello. My questions to developers of DNG concern the DNG format, into which I have been converting all RAW photos, considering that DNG is a complete analogue of RAW. I use Canon equipment. 
1. I recently have found that in many photo contests, if a photo reaches the final and claims prizes, confirmation of the rights to this photo (authorship) in the form of RAW files is required, and the DNG format is not considered as such. 

2. Once I had a claim about a Canon lens purchased - on specific photos as an example. The support required me to submit RAW files. The DNG files were not accepted by Canon support and I was told that they lacked some important information. 

Question 1. Please confirm that when converting RAW to DNG some information is lost, that 
a) does not allow to identify the authorship of the photo, 
b) does not allow to perform photo equipment service support.
Please indicate which information is being lost. 
If the statements written above are incorrect, please give a professional refutation. 

Question 2. What recommendations can you give to avoid the problems described above when using DNG?

I believe that these issues are very important for many photographers around the world.
Thank you!
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straannick

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Posted 3 months ago

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David Converse

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Demanding a RAW file to confirm ownership is meaningless. What if you shot using JPEG? Or on film?

Canon would need to let you know what data is missing. Many vendors have their own proprietary data that is not industry-standard and the DNG spec wouldn't deal with that. I'm not sure why its a big deal- shoot a sample photo and send the RAW file.

Or, embed the RAW inside the DNG.


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straannick

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Thank you, David!
1. Regarding the photo contest, it would be more correct to say about the authenticity of the photo, not about the authorship. Here is a quote from the rules of the one contest in my translation:
"Also, in order to establish authenticity, it is necessary to provide RAW files (.CR2, .NEF, .ORF, .PEF, etc.) or original uncorrected JPEG files ... DNG files are allowed only if they are the main format of the RAW camera"

2. Here is the answer of Canon support in my translation:
"ORIGINAL files in both JPG and RAW format contain extensive service information based on which we can often draw some conclusions. Any conversion of the original files leads to complete or partial loss of it and partial or complete loss of even standard EXIF ​​information. This does not allow us to make any reasonable assumptions about the reasons for the occurrence or the presence of problems when analyzing images. Converting original RAW files to DNG format leads to a loss of debug information. We can not comment on whether there is a loss in image quality and the possibilities of its processing in this transformation."

I use old Canon EOS 6D camera.
(Edited)
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Todd Shaner, Champion

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It's my understanding that Adobe includes all camera manufacturer proprietary data in the DNG file in MakerNotes. Adobe will sometimes support a new camera model with a new feature such as Canon's 'dual-pixel' technology before supporting that specific feature. In most cases Adobe will attempt to support the new feature in an update, which they did for Canon 'dual-pixel support in LR 6.8.

https://helpx.adobe.com/x-productkb/multi/editing-canon-dual-pixel-raw-cr2.html

As far as authorship is concerned the camera embedded copyright information in a raw file cannot be overwritten using LR, but there are many other metadata editors that can. Given that fact I don't see how a camera raw file proves authorship any better than a DNG file. Perhaps someone else landing here knows otherwise and will respond.

https://en.wikipedia.org/wiki/Comparison_of_digital_image_metadata_editors




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David Converse

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All three of your statements are subjective, not objective. There is no definitive answer that will cover all situations.

What matters more is, will DNG fit YOUR specific needs? Apparently the answer is no.
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Todd Shaner, Champion

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David, just our of curiosity do you convert your files to DNG file format on import and delete the raw files? If so you can explain WHY you do so and WHAT benefits that provides you over the raw file format? That would be helpful to the OP and myself. Thank you.
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David Converse

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Do I? Absolutely not.
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straannick

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Todd. Given the problems we are discussing and to which Adobe engineers are not responding, your question can be summarized as: "why there is a DNG format and what is the point of using it?" :-)
(Edited)
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Todd Shaner, Champion

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Adobe's objective in creating the DNG specification was to establish a "standard" file format that could be adopted by camera manufacturers and software developers. To date many camera manufacturers have adopted DNG file format, but the major manufacturers (Canon, Nikon, Sony) have not. Why?

This is a very competitive market and camera manufacturers maintain their product sales by offering proprietary and sometimes patented "new features," which will never be supported by the Adobe DNG specification. If you own a camera with one or more of these unsupported features your only option for using them is the "original" proprietary camera raw file or camera JPEG file. In fact adoption of these features in the DNG specification makes them no longer proprietary and could possibly affect the manufacturer's patent rights. I don't see this situation changing in the future, but camera manufacturers have worked with Adobe to support specific features such as built-in lens profiles.

So back to your question, "Why there is a DNG format and what is the point of using it?" I've provided two examples where (to me) DNG file format is useful, which are Photomerge Panorama and HDR DNGs and Lossy DNGs. I also convert raw files to DNG file format for troubleshooting in the forums and for sharing with family and friends who also use Lightroom, but I always save the original raw file.

Here's what Adobe says:

https://helpx.adobe.com/photoshop/digital-negative.html#key_benefits

To see what others say Google raw versus dng.
(Edited)