DNG Compression

[Ricoh]

Just got a brand new M240, reading the user manual it states:
The standard DNG Format is used for storage of completely unprocessed raw picture data.
The available compression for DNG format:
- is loss free, ie it does not cause any deteriation in quality;
- retains all of the post- editing performed on the image data;
- allows faster saving;
- takes up less memory space.

My question: is there something lost in the translation, or is this correct. If I select DNG Compression will anything be lost compared to uncompressed DNG? I'm using LR5.7 as my raw processor. Does it know when it's importing compressed DNG such that it can be reversed, ie uncompressed, to enable the full data file to be available for image manipulation?

Thanks for any assistance.

 

[willie_901]

If the compression is lossless then no information is destroyed. Instead of filtering (eliminating) uninteresting data (e.g. frequencies associated with photon noise in bright regions such as skies), the compression algorithm detects repeating patterns of zeros and ones and replaces them with compact code... a.ka. a look up table.

When the DNG file is uncompressed, the code recreates the original data patterns.

LR will uncompress lossless DNGs with no loss of information.

Lossy compression is more common and some version of LR (I forget what 5.7 offers) also support a lossy compression option when non-DNG files are converted to DNG. This should not be relevant to lossless in-camera DNG compression. However, you might want to make sure this option is not selected in case you convert negative scans or other non-Leica raw files to DNG. If the lossy DNG compression option is invoked in LR's Preferences,
I don't know if a Leica lossless DNG file could be converted to a lossy DNG file using LR using the "convert to DNG" tool in the Library drop-doen menu. But it would not shock me if it did.

 

[Ricoh]

Thanks willie 901.

 

[JPSuisse]

I agree with Ricoh on the camera part. What I don't understand though is what LR is really doing to DNGs.

There are numerous options in the tab Lightroom > Preferences > File Handling. Also, I have caught Lightroom making changes to my DNGs on several occasions without me having made any attempt to save the DNGs via the LR menu!

I have finally resorted to the following approach:
1.) Tag photos with metadata usuig ExifTool
2.) Copy the file to the pictures directory
3.) Import into LR using the settings in the attached picture.

You will note therefore that I save a DNG file that I do not process. LR may or may not be loss free depending on the import options. But, I am pretty sure that it *MAY* change the DNG version to a different version thereby limiting compatibility.

Note: I am generally using LR2 and LR4.

Good luck, Adobe's products are always a mess with often mission critical info (purposely?) not communicated to the user. Though that having been said, LR (and Dreamweaver 8 as acquired from Macromedia) is about the best they had with this regard. Although I never used it, the competition with Aperture did them good. Too bad its gone now.

John

 

[Doug]

JP, that function you illustrated is, I'm sure, intended to offer the option of creating DNG files out of NEF and PEF, etc raw files upon import. All my digital cameras save their raw files as DNG either natively or as an option, so I don't need to do any conversions. Though others might, and that would be the only reason I can think of to use that DNG creation feature in LR.

Personally, I'm happy to let my computer's file system handle file management chores, and keep LR's sticky fingers out of it! 🙂 With a card reader, I connect my SD card to the computer, showing up as an external drive, and copy its contents to a new folder/directory placed on my computer along with others of its kind so I know where it is and can deal with it directly at will. I then direct LR's attention to its location in the directory and "import". But the files just stay where they are and are not affected in any way. LR just knows where they are and saves editing details in its own database.

Before this "import" I will bulk-rename the DNGs according to my filing system, and possibly also adjust their EXIF data to reflect use of a non-native lens for example. And this is also the time I'd use CornerFix as needed...

Doug

 

[jaapv]

There is another advantage: If a format is not recognized (yet) by LR, converting the file to DNG will mostly allow one to open it.

 

[willie_901]

There is another advantage: If a format is not recognized (yet) by LR, converting the file to DNG will mostly allow one to open it.

This advantage is important.

The camera manufacturer does not waste money developing and maintaining a redundant proprietary raw format.