DXO DNG Workflow

[iugradmark]

Thanks for the intelligent discussion on this subject. You guys are way above my pay grade on understanding this stuff. The genesis of my questions came from the fact that although I am running on Windows XP SP2, I am not getting an imbedded preview when I open in IView. I cannot even find an option in the menus where to select this.

To create the preview after I create the DXO DNG, I have opened the file in ACR and created an Adobe DNG complete with full size preview. When I do this, am I modifying the adjustments, etc. that DXO makes. I am not making any adjustments inside ACR, just doing a save as.

I appreciate the issues this creates with extra steps, etc.

Mark

[AlanDunne]

Chuck,

you don't give yourself enough credit. It looks like you "get it". I am glad that DXO seems to be providing reasonable support for your issue. I hope it works out and they solve the bug in the viewer.

DXO likes to position their product as "automatically" adjusting images to make them better. For certain things this is true. For corrections such as distortions, chromatic aberration, and even to a certain degree lens sharpness, they can be done very well automatically. This is because DXO has measured the performance of lens/body combinations and uses this information in the correction. This is physics. I am sure there will be unit to unit variation, but there would be a statistical trend that could be measured and then compensated for.

For tonal corrections, automation is much more difficult to consistently do well. Sometime the algorithm guesses well, sometimes not. This is not unique to DXO. The same applies for ACR when the auto corrections are enabled. Tonal corrections are dependent upon the image.

So when I use DXO I try to play to its strenghts and minimize its weaknesses. In general I prefer ACR for tonal work, and in general most of my images only go through ACR as a raw converter. But some images require DXO and for those I generally output a DNG and to tonal/curve, WB, crop, etc in ACR.

We spend way too much time on all these technical things. I am currently studying the works of Cartier-Bresson and may go look for a Leica...

I know what you mean. I want to spend far more time behind the lens than the computer. But then again, I would rather spend more time behind a computer than the old days of in the darkroom. I must confess that I do miss that initial wow when a B&W image starts showing its form in the developer tray. But I don't miss the chemicals.

But technology has always been a part of photography. It has always been part art, part craft, and part science. For all his artistic merit, Ansel Adams spent an enormous amount of time fretting over the photographic technologies of his day. He did a lot of technical testing and characterization so that he could understand his media. That was true for his film and his prints.

At the end of the day we cannot escape the technology. I am gald, however, that forums such as this exist to share knowledge and provide guidance. I could not imagine "going it alone".

Cheers ... Alan

[AlanDunne]

Thanks for the intelligent discussion on this subject. You guys are way above my pay grade on understanding this stuff. The genesis of my questions came from the fact that although I am running on Windows XP SP2, I am not getting an imbedded preview when I open in IView. I cannot even find an option in the menus where to select this.

To create the preview after I create the DXO DNG, I have opened the file in ACR and created an Adobe DNG complete with full size preview. When I do this, am I modifying the adjustments, etc. that DXO makes. I am not making any adjustments inside ACR, just doing a save as.

I appreciate the issues this creates with extra steps, etc.

Mark

Mark,

it seems that I am the only one getting the embedded preview from a DXO DNG that can be seen in IVMP. I will have to do some tests over the weekend and see if there is anything obvious that I am doing that is outside the norm. I will try to report back early next week.

Cheers ... Al

[AlanDunne]

One and all,

here are my findings after experimenting with DXO output to the DNG format:

• I now think I know why DXO outputs a linear DNG. It looks like the DNG has actual RGB modifications in it and not just metadata updates. With some test images I made radical adjustments so that they would be obvious. These were seen in the Bridge and ACR previews, which are not based on the embedded jpeg preview of the DNG. On that linear DNG file it was possible to perform ACR edits which were visible in the Bridge preview, and also in the DNG embedded preview (once that preview was re-built after closing ACR).
• DXO 4.1 does not output a full size embedded preview. When I processed a D200 raw NEF image, then imported the image into IVMP, the preview was 200x300 pixels.
• After running the DXO DNG output through ACR, with my settings for embedded full size DNG, the DXO DNG now includes the full size preview. When I go to IVMP and look at the preview via the Media pane, I now see the full size D200 image and it refllects the ACR adjustments. A re-build operation then sync'd up the IVMP thumbnail with the preview.
  

Cheers ... Alan

[cabrackett]

Alan
Forgive me for beating a dead horse, but here goes:

1. I have finally figured out that "linear" (as in Linear DNG) has nothing to do with gamma in this context, but really means a demosaiced file. ACR will read and edit such a linear dng, and in fact DxO corrections do appear in that linear dng file. (I don't know what I was doing wrong before, but I did what you did and the corrections do appear.) The term "linear" has appeared in too many contexts without sufficient clarification. I find even Fraser's book confusing on this point.

2. The Bridge and ACR previews do in fact become full size after running the dng file through ACR and then recaching in Bridge.
 also find that the Annotations in the metadata do get stripped as advertised by DxO.

3. The iViewMP preview does then become full size also after a re build.

So all is well.

After running the DXO DNG output through ACR, with my settings for embedded full size DNG, the DXO DNG now includes the full size preview.

But the above quote confuses me one more time. When you say that the DXO DNG now includes the full size preview, do you mean that when you view the DNG file in the DXO viewer you see the full size preview? I still see nothing.

Thanks for your help,

Chuck

[AlanDunne]

Chuck,

I can see how I was not too clear ...

I actually do not use the DXO viewer. After a DXO "process" session, I go straight to Bridge where I use ACR for further work on the image. At the end of ACR editing, ACR crunches through it calculations and produces a full size embedded preview on the DNG because that is how I have set up my ACR preference. But of course at this time I still have not seen the embedded preview in the DNG because Bridge uses its own cached previews. The first time I actaully get to see the DNG embedded preview is when I import the image into IVMP and display the media tab.

What I did in my experiment was to import the DXO DNG directly into IVMP before touching it in ACR. When I look at the media tab for that image, it was small and the size was stated to be 200x300 pixels. So I presume that was the size that DXO embedded. Now if I then take that image and do an ACR adjustment, then look at the media tab in IVMP it now shows the full size embedded preview. Now if those ACR adjustments made visible modifications to tonality or colour, the IVMP thumbnail did not show these changes until a re-build was performed.

I don't use the DXO viewer because I don't really see the value. I guess I use Bridge as the viewer because it has more flexibility for adding metadata and hosting ACR.

One thing that DXO does not do is respect metadata edits in XMP. I wish it did. For example if I add a copyright notice or keywords to the NEF image in bridge, those are reflected in sidecar XMP files. The DNG output from DXO operating on the NEF file only contains the metadata that was already in the NEF itself, such as camera EXIF. It is little things like this that make DXO less friendly from a DAM perspective. One of these days I will put in a feature request.

By the way, you are correct that linear seems to mean many things to many people. The DNG output from DXO is clearly demosaiced. You can see that in the file size, and the fact that Bridge/ACR will preview the DXO changes even though Bridge/ACR has no knowledge of the proprietary DXO processes. This is probably the correct choice for DXO to have made. It makes the DXO corrections portable to other applications at the expense of making them permanent. You have to keep the original raw file in order to get back to pre-DXO corrections to start again.

Because of the "permanance" of the DXO edits, from a DAM perspective I treat the DXO DNG as a derivative file, on the journey to a TIF master. I don't treat the DXO DNG as a raw or original file, even though it is DNG format.

Hope that helps. Perhaps it was more long winded than I originally intended ...

Cheers, Alan

[cabrackett]

Alan

A-HA! Enlightenment.


Thanks for the detail and your efforts.

Chuck

[cabrackett]

Alan
Last Thought

If these changes are permanent, I guess the only advantage to using the DNG format for DXO output (over TIFF) is that you get to use ACR for further touch-up before going to photoshop for a real master image. And what do we lose in ACR for having a linear DNG with the DxO changes frozen in place other than not being able to retract those changes?

Chuck

[AlanDunne]

Chuck,

perhaps you give me too much credit. I am no expert on raw conversion.

I believe one thing you loose when operating on a linear DNG compared to normal is that ACR is not performing the demosaic operation. If you think ACR is particularly adept at demosaicing, then that is something that you loose. My gut feel is that demosaicing is where ACR is good, but perhaps not best in class. There is lots of discussion about this where others have shown, for example C1, to be better. I find DXO on some images to outperform ACR for detail extraction. For 99% of my images the DXO benefit for this is not worth the loss in workflow efficiency.

I would also guess that ACR would not be able to do highlight recovery on the linear DNG. Note that this is a guess. ACR has been noted as being particularly good for highlight recovery. But DXO can do highlight recovery as well, so you don't loose this capability end to end, but it moves to a different location in the workflow.

Further guessing, or perhaps I would classify this as speculation ... the ACR up-rezing may not be as good on a linear DNG  compared to operating on a mosaic data file.

Perhaps if there are other people still following this thread that have more knowledge on the raw conversion process, they could better answer you question. I only use bold text here to draw attention to the fact that I really haven't answered your question very well.

One other question that people may have about this process ... are there any benefits to performing edits on a de-mosaiced linear DNG compared to TIF? For me the answer is yes. Using ACR I can far more efficiently perform tonal changes and colour changes in ACR, especially on groups of images, than I could on TIF's one by one in Photoshop. The only downside is that those tonal and colour edits on the DNG's are global. If I need to do selective work then I must go into Photoshop where I can take advantage of the layer masks. Final masters are in TIF and I have ouput specific sharpening layers applied there as well.

Hope that helps, and I invite others to comment about your raw conversion question.

Cheers ... Alan

[peterkrogh]

Alan,
I think you have outlined the landscape pretty well - at least in terms of general issues and questions. I'll ping someone who might know what DxO is doing under the hod.
Peter