DNG conversion comment from The Online Photog

[Peter Frahm]

Mike Jonhston from the Online Photographer made this entry regarding DNG conversions for use in versions of Photoshop that don't support particular cameras. Tons of people who don't want to keep upgrading Photoshop are using this method to have access to their RAW files.



From The Online Photographer:

"It appears that yesterday, I was guilty of the common mental error of believing what I wanted to believe. I like the idea of Adobe DNG (digital negative)—a vendor-independent raw standard that works across platforms and promises unlimited future support. The DNGs I was shooting with the K20D were opening up in my older copy of Photoshop, and they looked great.

But appearances can be deceiving. Go into ACR (Adobe Camera Raw) and look at the numbers in the "White Balance" box, and you'll notice they can be way screwy—on my DNGs, temperature was 7000 Kelvin for one picture and tint was +97 for another, in fairly neutral light. That's not right. Carl tells me that's because the LUTs (lookup tables) are not proper for the camera and the raw file is not being unpacked properly. He wrote about this last year in his series of posts on the K10D, when he noticed the raw files didn't behave right until he got a version of ACR in which the K10D was supported.

So, even if you're using DNG, it's still necessary to use a version of ACR (or whatever raw converter you choose) that specifically supports the K20D (or whatever camera you own). With Adobe products, you need ACR 4.4 or Lightroom 1.4 to get K20D support. ACR 4.4.1, the latest version, is not compatible with versions of Photoshop prior to CS3, although it is usable with updated copies of Lightroom and with Photoshop Elements later than version 4.0 for Macintosh and 5.0 for Windows.

Carl is currently shooting PEFs (that's Pentax's proprietary raw file type) because they're smaller files, then immediately converting them to DNG using Adobe DNG Converter, which is a free download."

http://theonlinephotographer.typepad.com/t...o.html#comments




With the numbers of people who are converting proprietary RAW files to DNG from many different cameras I'm wondering what impact this has on the actual images?? Does the conversion and use of DNG from a camera that is not supported by PS leave those people missing something..something important?

Seems significant but I'm not sure I understand how it affects the actual end image...

[Panopeeper]

A program workign with DNG files generally does not need the knowledge of the particular camera model; that's the basic idea of DNG, although in practice this does not always work. Anyway, ACR's rendering of a DNG file is only as good as the file content is. Pentax made an error in the DNG files (with the K20D as well), and ACR had to be tweeked to accomodate that error.

Camera manufacurers generally have a relaxed attitude towards standards. TIFF rules are regularly violated by Canon, Nikon, etc. and programs processing those files have to be prepared to process such files, which should be rejected. In case of Pentax, the error in the white balance is caused by incorrect specification in the DNG files. The temperature and tint are calculated by the raw processor based on the white balance specification AND on the color conversion matrixes, and that's where Pentax made the error.

[Jonathan Wienke]

The whole issue is only relevant if you insist on using the "as shot" WB setting. Camera makers regularly try to break compatibility with standards for WB data so that only the manufacturer's proprietary crapware will read the file correctly. Nikon even deliberately encrypted this data on some of its cameras until a firestorm of negative PR forced them to stop.

[Panopeeper]

Camera makers regularly try to break compatibility with standards for WB data so that only the manufacturer's proprietary crapware will read the file correctly

There is no standard of WB specification regarding the native raw files. The existing WhiteBalance tag of Exif is notmuch worth; it contains values like "Daylight", etc.

However, the problem occured with DNG files created in-camera. If a manufacturer subscribes to support DNG and actually creates DNG files, then those should be correct.

In this particular case the issue was not the reluctance but the incapacity of the manufacturer to make it properly.

In native raw files I found cases with violations of the standards, which are obvious mistakes (programming error), other cases, which are intentional, and there are cases, which I can not rate. Sometimes I think the manufacturers make fun of the independent software producers.

[DarkPenguin]

What about the adobe equivalent of profiles?  I presume every camera is a little different.  (Beyond the stuff mentioned in the ACR tutorial.  I'm referring to a k10d vs a d80.)  Does the DNG standard account for that?

[Panopeeper]

What about the adobe equivalent of profiles?  I presume every camera is a little different.  (Beyond the stuff mentioned in the ACR tutorial.  I'm referring to a k10d vs a d80.)  Does the DNG standard account for that?

If you mean the color profile, yes, the DNG specification does contain elements describing the sensor's color characteristic, in form of matrixes used in translation between color spaces. However, it is questionable if this method is good enough to describe the characteristics of all sensors under all illuminations.

[madmanchan]

I posted this in the comments in Mike's blog, but just in case you missed it:

The white balance issue with the Pentax 20D's DNG files is actually a Pentax bug. The bug involves an incorrectly-computed color matrix being embedded into the DNG by the camera. It has nothing to do with Camera Raw. I believe Pentax is working on a fix.

With the fix in place, you should be able to open up the Pentax K20D DNG files with older versions of Camera Raw, even ones that were around before the K20D was released.

In other words, Mike's original statement, which is that he could take a K20D DNG file and open it in Camera Raw without waiting for an update, is perfectly true ... except that there is a bug in how these DNG files are being created by the camera. The files will still open fine, but the WB will be wrong.