Author Topic: DNG Files  (Read 6144 times)

RJM

  • Regular
  • **
  • Posts: 20
    • View Profile
DNG Files
« on: November 23, 2009, 11:57:08 pm »
I've been checking out Lightroom 3 beta, and after a few tutorials I'm really starting to like it.  However, it only has two coversion types one is TIFF and the other DNG. What is DNG?  With UFRaw...it converts to sRGB, which I believe is 8-bit.

So, what is DNG?  Pro's, Con's.  Can GIMP read those files?

Thanks.

Roger
« Last Edit: November 24, 2009, 07:00:21 am by monoceros84 »

mac

  • Regular
  • **
  • Posts: 13
    • View Profile
Re: DNE Files
« Reply #1 on: November 24, 2009, 06:45:51 am »
I've been checking out Lightroom 3 beta, and after a few tutorials I'm really starting to like it.  However, it only has two coversion types one is TIFF and the other DNG. What is DNG?  With UFRaw...it converts to sRGB, which I believe is 8-bit....

As it happens, there's a recent forum thread here:

http://forum.meetthegimp.org/index.php/topic,750.msg5978.html#msg5978

Using RAW (as DNG seems to be) is good.  Use UFraw to 'develop' the photos before you edit in GIMP.  Or install the UFraw plug in for GIMP, so that when you open the .dng file with GIMP, it is first opened in UFraw so you can do the initial processing there (in 16 bit - also good) before doing the rest in 8 bit in GIMP.  Mathias summarises this in the above thread.

Also, Google is your friend:
http://en.wikipedia.org/wiki/Digital_Negative_(file_format)

HTH

mac

monoceros84

  • Administrator
  • Sr. Member
  • ***
  • Posts: 1898
    • View Profile
Re: DNG Files
« Reply #2 on: November 24, 2009, 07:18:33 am »
DNG is the Adobe standard for a RAW file. Like CR2 is from Canon or NEF is Nikon. So I guess Lightroom can convert pixel images (as JPG or PNG) into TIFF and RAW images into DNG.

As far as I know DNG is slightly smaller than usual RAW files and it's more uniform. Most software is able and will be able to read this - whereas the camera internal RAW file format often changes. I heard of people converting all their RAW files into DNG for those reasons. You need to decide on your own if those small improvements are worth the time.

To your question: GIMP can't read DNG but UFRaw (and the GIMP plug-in of it) can.

BTW: sRGB has nothing to do with 8bit. sRGB tells which colours can be represented. It's another questions HOW they are represented. To make up a little picture: imagine you have a sensor that can measure from 0 to 10 volts, this range represents the colour space in our example. But the sensor can only display integer values, this represents the bit depth. You could also measure float point values if you had a higher bit depth. Or you could measure, say, -2 to 12V if you had a bigger colour space. I hope it's understandable!
Cheers,
Mathias

Visit this site about my photography, my experiences in Norway and my blog:
http://www.gedankenquirl.de (German language)

RJM

  • Regular
  • **
  • Posts: 20
    • View Profile
Re: DNG Files
« Reply #3 on: November 25, 2009, 03:33:52 am »
Matthias, regarding workflow - I am testing/learning LIghtroom 3 beta and am trying to get an organized photo development system going.  And I'm trying to wrap my brain around all of the elements and options to establish how I can optimize my workflow.  

So there are the various file formats (DNG, RAW, XCF), and the applications (GIMP, Lightroom, UFRaw).  Now, in a previous posting I was also struggling with this similar issue which you helped me with, and maybe I should have tacked this on to that conversation...But here are my thoughts, and hurdles regarding this: I would like to use LR for organization, image management and for most of my image processing and GIMP for my works of art.  But LR has some slick, powerful and advanced tools, that seem to rival those of UFRaw.

The trouble I"m having is with the file formats and which to use and when.  For instance, I"m working on a photo in LR and realize I need to remove someone's head or foot, and want to do that in GIMP.  Should I export it as a DNG (or TIF) file, then use UFRaw (only - since LR seems to perform the like changes as UFRaw) to export it as a sRGB file for GIMP?  Then once I'm done with GIMP, export it as a XCF file and as a JPEG for the internet?

Can you feel my pain?  ???

I appreciate your patience and expert advise.

Roger
« Last Edit: November 25, 2009, 04:52:24 am by RJM »

monoceros84

  • Administrator
  • Sr. Member
  • ***
  • Posts: 1898
    • View Profile
Re: DNG Files
« Reply #4 on: November 25, 2009, 07:16:35 am »
But LR has some slick, powerful and advanced tools, that seem to rival those of UFRaw.

The Lightroom RAW converter definitely overtops UFRaw. If you are not too much in the Open-Source-Thinking I would recommend to use this instead.

The trouble I"m having is with the file formats and which to use and when.  For instance, I"m working on a photo in LR and realize I need to remove someone's head or foot, and want to do that in GIMP.  Should I export it as a DNG (or TIF) file, then use UFRaw (only - since LR seems to perform the like changes as UFRaw) to export it as a sRGB file for GIMP?  Then once I'm done with GIMP, export it as a XCF file and as a JPEG for the internet?

Well, as said above I would develop your RAW files in Lightroom. If you are finished after that you should be able to save the result as JPEG. If you want to open the result in GIMP for further editing I would save the intermediate file as TIFF to get the best quality. Somehow Lightroom should also be able to directly send the result to GIMP without saving it in between. At least that's what you can do with other editing software. But I have never used Lightroom that far to know exactly how it works.
After GIMP I recommend saving it as a XCF file. Only doing so enables you to always make changes afterwards. And of course export it as JPEG since I doubt that Lightroom can read XCF.

You see, I always save my final results as JPEG to have them available for viewing, browsing, publishing. And I always save my edits as XCF. TIFF would only be needed for intermediate temporary files. And DNG, well, as I said they would replace your camera RAW files. Decide on your own to keep them or to convert them all into DNG.

I appreciate your patience and expert advise.

Wow, thank you!  :)
Cheers,
Mathias

Visit this site about my photography, my experiences in Norway and my blog:
http://www.gedankenquirl.de (German language)

mramshaw

  • Lives here ;-)
  • ***
  • Posts: 547
    • View Profile
Re: DNG Files
« Reply #5 on: November 25, 2009, 09:38:52 pm »
If you want to open the result in GIMP for further editing I would save the intermediate file as TIFF to get the best quality.

Good thread. I'd recommend PNG over TIFF as PNG is more of an open standard so less likely
to change unexpectedly. On the other hand, professional uses are probably more likely to want
TIFF. But if you are just planning to process in GIMP, 16-bit PNG is probably your best option.

RJM

  • Regular
  • **
  • Posts: 20
    • View Profile
Re: DNG Files
« Reply #6 on: November 25, 2009, 11:12:13 pm »
Matthias, thanks for your suggestions and for clearing this up for me.  That's exactly what I needed to hear.

Roger

monoceros84

  • Administrator
  • Sr. Member
  • ***
  • Posts: 1898
    • View Profile
Re: DNG Files
« Reply #7 on: November 26, 2009, 07:53:56 am »
If you want to open the result in GIMP for further editing I would save the intermediate file as TIFF to get the best quality.

Good thread. I'd recommend PNG over TIFF as PNG is more of an open standard so less likely
to change unexpectedly. On the other hand, professional uses are probably more likely to want
TIFF. But if you are just planning to process in GIMP, 16-bit PNG is probably your best option.

You are right. I just started where Roger stopped. He told that Lightroom can only export TIFF and DNG. That's why I have ignored PNG. But of course, if it was possible, I would also prefer PNG.
Cheers,
Mathias

Visit this site about my photography, my experiences in Norway and my blog:
http://www.gedankenquirl.de (German language)

dogwatcher

  • Regular
  • **
  • Posts: 56
    • View Profile
Re: DNG Files
« Reply #8 on: December 10, 2009, 06:34:10 am »
As far as I remember, PNG is troublesome if you want to use all the metadata.. EXIF and stuff.

I was forced to use PNG for a while as the export function of RawTherapee was buggy with certain RAW files...  (TIFF export was messed up) and always lost my EXIF infos... and according to

http://www.digitalpreservation.gov/formats/fdd/fdd000153.shtml
(..see section "Self-Documentation")

PNG is indeed not too friendly in this respect.

I switched back to TIFF.. I think it's highly unlikely that TIFF will be changed fundamentally in the future, it has become a de-facto standard like JPG...

monoceros84

  • Administrator
  • Sr. Member
  • ***
  • Posts: 1898
    • View Profile
Re: DNG Files
« Reply #9 on: December 10, 2009, 06:51:38 am »
Ah, very important information. Thank you!
Cheers,
Mathias

Visit this site about my photography, my experiences in Norway and my blog:
http://www.gedankenquirl.de (German language)

mac

  • Regular
  • **
  • Posts: 13
    • View Profile
Re: DNG Files
« Reply #10 on: December 10, 2009, 07:19:49 am »
...As far as I know DNG is slightly smaller than usual RAW files and it's more uniform. Most software is able and will be able to read this - whereas the camera internal RAW file format often changes. I heard of people converting all their RAW files into DNG for those reasons...

I normally use Ubuntu with the Gnome desktop, which uses the F-Spot photo organiser.  However, I've been having a play with Siddux and KDE4, to see if DigiKam would be better.  I just noticed that DigiKam can convert camera RAW files (I use Nikon .NEF) to .DNG;  and the user guide recommends .DNG for the reason Matthias gave -- camera RAW is subject to proprietary change that may render your files unreadable.

I was wondering how the DigiKam RAW converter compares with UFraw.  Does anyone have experience of both to share?  (AFAICS, F-Spot can only read .DNG, but cannot convert from RAW to DNG.  Am I right about that?)

dogwatcher

  • Regular
  • **
  • Posts: 56
    • View Profile
Re: DNG Files
« Reply #11 on: December 10, 2009, 10:36:53 am »
...As far as I know DNG is slightly smaller than usual RAW files

Not necessarily.... The Pentax PEF format is usually smaller than a comparable DNG file.

 At least the the DNG files the Pentax K10D and K20D can write too (you can choose between the two formats, which is quite nice). Just an example.

Quote
... and it's more uniform. Most software is able and will be able to read this - whereas the camera internal RAW file format often changes. I heard of people converting all their RAW files into DNG for those reasons...

Well, yes and no... it's indeed a pain with all these proprietory formats, but DNG doesn't necessarily save your day.

Example: The Pentax K20D and Samsung GX20 are able to write DNG files.. in fact, the two cameras are almost identical. But for whatever reasons Samsung decided to use a different camera profile, which results in odd behaviour of the colors if you try to open a GX20 RAW file in RawTherapee or UFRaw without a specific camera profile. In other words: Having a DNG file in your hands may not mean you can do anything useful with it... it may be readable, you can see "something" in your RAW-program of your choice, but otherwise it may be totally messed up.

So much for the "archive" aspect of DNG.. It's not THE solution to all your RAW troubles.


monoceros84

  • Administrator
  • Sr. Member
  • ***
  • Posts: 1898
    • View Profile
Re: DNG Files
« Reply #12 on: December 10, 2009, 12:07:38 pm »
Not necessarily.... The Pentax PEF format is usually smaller than a comparable DNG file.

 At least the the DNG files the Pentax K10D and K20D can write too (you can choose between the two formats, which is quite nice). Just an example.
Ah, nice to know. It would be interesting to convert one of those PEF into DNG using different software. And then compare the file size of the camera's DNG, of the manual created DNG and of the original PEF.

Example: The Pentax K20D and Samsung GX20 are able to write DNG files.. in fact, the two cameras are almost identical. But for whatever reasons Samsung decided to use a different camera profile, which results in odd behaviour of the colors if you try to open a GX20 RAW file in RawTherapee or UFRaw without a specific camera profile. In other words: Having a DNG file in your hands may not mean you can do anything useful with it... it may be readable, you can see "something" in your RAW-program of your choice, but otherwise it may be totally messed up.

That's not a problem of the RAW file but of the colour profile or the camera sensor. You can apply whatever profile you want to your RAW developers.
I was rather talking about not being able to read your proprietary RAW files one day. Imagine Canon invents another RAW format (or stops using them), new software will not handle the old format anymore and one day the old software is not running anymore on the new operating systems. True, that's quite unlikely, but that was the situation I meant.
Or more likely: You change from Canon to Nikon and want to use the manufacturer's RAW developer. Now you need two of them to be able to read your new and old files.

So much for the "archive" aspect of DNG.. It's not THE solution to all your RAW troubles.

Of course not. But to some of them :D I also stick to my proprietary format because I am not that much afraid of the situation mentioned above. But I can understand people converting into DNG.
« Last Edit: December 10, 2009, 12:12:03 pm by monoceros84 »
Cheers,
Mathias

Visit this site about my photography, my experiences in Norway and my blog:
http://www.gedankenquirl.de (German language)

mramshaw

  • Lives here ;-)
  • ***
  • Posts: 547
    • View Profile
Re: DNG Files
« Reply #13 on: December 11, 2009, 11:50:16 pm »
I was wondering how the DigiKam RAW converter compares with UFraw.

I got into Gimp after finding that DigiKam did not meet all of my needs. It does meet most of my
needs but sometimes you just want to do serious editing. I like the Vivid option and the Refocus
stuff. That said, I'd have to say the RAW conversion is not as good as 'ufraw'. It's still useful,
but not my first choice for RAW conversion. Given how actively DigiKam is maintained, I expect
Gilles will soon have DigiKam up-to-speed, so keep an eye on DigiKam. But for now I use 'ufraw'.

mac

  • Regular
  • **
  • Posts: 13
    • View Profile
Re: DNG Files
« Reply #14 on: December 12, 2009, 07:02:13 am »
...I'd have to say the RAW conversion is not as good as 'ufraw'.

Thanks for this.  I'm happy with ufraw, but wanted to check if it would be worth spending time learning to use the digiKam RAW converter before I spent hours on it.