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08-29-2008, 06:47 AM   #1
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What is it exactly and how does it differ from RAW?

08-29-2008, 06:51 AM   #2
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DNG is RAW. It is just Adobe's take on the RAW file format.

Pentax has PEF, Canon has CR2, Nikon has NEF.

Adobe's DNG is an open standard, and Pentax was the first company to offer DNG encoding as an option.
08-29-2008, 07:13 AM   #3
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QuoteOriginally posted by JohnnyDop Quote
What is it exactly and how does it differ from RAW?
As ftpaddict has already said, DNG is raw - a raw format defined by Adobe. On a Pentax K10D/K20D, if you save your raw files in DNG format rather than PEF, you get all the same info, it's just in a different file format. I've talked to an engineer at Adobe and been assured that everything in the PEF file is there in the DNG.

DNG has some advantages. It's not tied to a particular hardware vendor (like Pentax, Nikon, etc.). It's fairly widely used and Adobe hopes it becomes nearly universal, the way .pdf has become. (I'm old enough to remember the days when pdf had competition from Corel and others.) New software sometimes supports DNG before it supports hardware-specific formats. That was for example the case with Light Crafts' LightZone, which has supposed the K20D's DNG files for a while, but which just recently released version 3.6 that supports the K20D's PEFs.

And, in theory, if DNG really does become very widely used, then your DNG files may be easier to read in the future than your PEF files will be (say, after Olympus buys Pentax in 2012 and the PEF format disappears).

All of those advantages are theoretical. And DNG is just one of the two ways to deal with the problem of all these different raw formats. The other approach is called Open Raw. You can read about it here:

OpenRAW | Digital Image Preservation Through Open Documentation

I haven't made up my mind yet about whether I like DNG or not.

On a more immediate and more practical level, here are a couple thoughts.

On the plus side, the Pentax K10D/K20D write DNG files faster than PEF files. The reason for this seems to be that the PEF files are compressed and compression takes a bit of processor time, while the DNG files are not compressed.

On the negative side, um, the DNG files are not compressed - which means they are bigger than PEF files, which means you get fewer DNG files to a card. Since I'm now mostly shooting with 8 GB cards, this is not really a big issue for me (although I can fill up an 8 GB card without too much effort).

Bottom line for me: PEFs are smaller on the SD card, and it's a snap to convert PEF to DNG later on the computer if I want to. I tried saving DNG for six months. Now I'm back to using PEF and will stick with PEF for a while.

08-29-2008, 07:19 AM   #4

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DNG is much more actually. It's a pretty open standard for including RAW data from various camera's, but Pentax is one of the few that allows DNG files to be created in camera.

As implemented by Adobe itself, DNG can include additional compression (in-camera DNGs are uncompressed) and additional metadata, including the adjustments and ranking information set by a user in Adobe's RAW enabled software, i.e. Lightroom and Camera RAW. Any RAW format by any brand can be converted to DNGs for use in these applications by the RAW converter provided by Adobe or automatically at time of import into these applications.

DNGs are thus a better archival format, as they contain all information in one file, both RAW data, metadata and basic post-processing information.

Note however that if you use the in-camera generated DNGs in non-Adobe software such as the Pentax Photo Lab software, you will not be taking advantage of all DNG features. The only advantage I identified in using in-camera DNG is that this format allows the use of RAW files out of camera's whose new proprietary RAW files are not supported yet by Lightroom or Camera RAW. This meant I could continue using my favourite software (Lightroom) and continue shooting RAW (with my K10D and later K20D) even if Adobe had not yet updated its software for PEF support out of these cameras. Once supported I did switch to PEF in-camera for the smaller filesize, but I still convert to DNG when moving my images onto my PC.

hth, Wim


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