No color profile tagging of DNGs?

[Carl F in MD]

Operating System: mac high sierra OS x 10.13.1
Exact Lightroom Version (Help menu > System Info): 5.7.1

Do DNG photos possess a color profile or, since this is still sensor data in a wrapper (from NEF-raw in my case), do we say there _is no_ inherent color profile? I had not been paying attention, but when (at last) I looked at my DNGs in Adobe Bridge, I was surprised to see "Color Profile: untagged."

Somewhere I read that LR operates in ProPhoto RGB working space, altho the full implications of this are over my head. Therefore, if my monitor is correctly calibrated, is what I see "as if" the data were ProPhoto RGB? (My monitor has a far more constrained gamut, I know, and interprets the picture data that it is given to display.)

Meanwhile, I see that when I export (or send to be edited in PhotoShop), then color profiles kick in -- for my exported 16-bit TIFFs I use Adobe 1998, and for my JPEGs I use sRGB, since they head for the Web.

Here's my puzzle: if I pass along the DNGs, how are they interpreted? I thought that when someone opens my images in a "smart" application with a calibrated monitor, that the app would read the color-profile tag and present the image accordingly. (As for the Adobe 1998 TIFFs.) But what happens when a non-Adobe app opens one of my DNGs? If it is a "smart" app, does it assume-by-default that the data (including the embedded XMP parametric adjustments) are "as if" ProPhoto RGB. Yikes!

This query must have been discussed often, but my search on this forum failed to turn up the topic.

Best from Carl

 

[clee01l]

Welcome to the forum.
A RAW file has no color space and there fore no color profile. Once converted to RGB, you must assign a color space (a color space being the envelop the encompasses all of the RGB color pixels). ProPhotoRGB is larger than AdobeRGB which is larger than sRGB. Since colors are being calculated during development, you want the largest color envelop to contain them. It is when you create a derivative processed image file that you want to choose the color profile that matches the destination media. (sRGB for generic monitors and AdobeRGB for generic printers.

 

[Johan Elzenga]

As long as the DNG contains raw data (DNG can also contain rgb data) then the color space is not yet defined.

A non-Adobe app cannot read the embedded parametric adjustments. It could read the values because those are in plain text, but because it does not have access to the Adobe raw engine, it cannot produce the same results from those values.

 

[Carl F in MD]

Thanks for the replies, very helpful. It was also helpful to be reminded that, although DNG is an excellent "open" and documented approach to managing photo-sensor data over time ("preserve the 'raw' for the long term"), it is also the case that one's Lightroom adjustments depend upon Adobe apps for proper interpretation. Thus the parametric adjustments are "more proprietary" than the DNG itself, and depend upon Adobe apps to a greater degree than than the underlying data in the DNG file.

This topic is on my mind because of work I do with the Library of Congress (I am now retired), and my concern to properly undertand implications for long term data management. For my own photos, to be left in an archive, I'll stick with my habit of (1) keep the DNG with parametric adjustments and (2) bake a TIFF to show what was intended.

BTW: tip of the hat to Peter Krogh, always a good advisor too.

 

[LouieSherwin]

Hi Carl,

When you create your TIFFs I suggest that you save them in ProPhoto RGB not a smaller color space. You can always convert to a smaller color space any time in the future as needed. Use sRGB for any images that are intended for viewing on the web but this is not recommended for archival purposes.

-louie

 

[Hal P Anderson]

On the other hand, if you merely want to show what was intended, you can update the preview JPEG that is stored within the DNG file. Metadata menu: Update DNG Previews & Metadata. This will create an embedded JPEG in the DNG with all your edits applied. This keeps everything in one place and takes up much less storage on disk.

 

[Carl F in MD]

Thanks for the additional information. I respect the advice to favor wider-gamut ProPhoto RGB but the special circumstance at the Library of Congress concerns their practices for scanning old materials (most color is 35mm color slides), where (after some deliberation), they ended up requiring contractor delivery of 16-bit Adobe 1998 RGB TIFF images. At LoC, many post-processing systems are in place (or under development) that expect to receive Adobe 1998, and my decision to make my TIFFs that way is to provide them with consistent inputs. But this raises the value of the also-archived DNGs, and I especially appreciate the tip on updating the embedded JPEG to represent the parametric adjustments.