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Author Topic: What is relationship between demosiacing and raw conversion?  (Read 1641 times)
dmward
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« on: June 11, 2014, 09:49:55 PM »
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Lightroom is a parametric editing program.
So, if I have a raw file, for example a Fuji X-Trans file from an XT-1, and convert it to DNG, does the demosiacing take place during that conversion or does it take place when the edits applied in Lightroom are applied when I export the file as a TIFF or JPG?

If I were to take a file and convert it to DNG and import into Lightroom and also take the original raw file and import it into Lightroom would the DNG be demosiaced in the DNG converter and then presented to Lightroom in a DNG "raw" data format that is different than the raw data presented to Lightroom by the manufacturer's raw format?
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Schewe
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« Reply #1 on: June 11, 2014, 10:54:13 PM »
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For the moment, ignore DNG as it doesn't really play a role here...

Demosiacing is only one part of the raw processing pipeline, in addition to demosiacing the raw data (usually a Bayer array), the raw processor must also make adjustments from camera color into a color working space. None of this is actually done to the raw file until it's actually processed into a rendered file such as tiff or jpeg. Until that time, the adjustments are stored in the .xmp sidecar file–hence the "parametric" edits...

As it relates to DNG, generally, unless you change to DNG settings to produce a linear DNG (a demosiaced, linear file) the DNG file contains the same raw data as in the original raw file. In this case, the DNG is simply a file format wrapper for the original raw data.
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dmward
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« Reply #2 on: June 12, 2014, 10:58:53 PM »
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Thanks Jeff.
I presume the same is true if the file is from a Fuji X system camera with a non-Bayer array.
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Schewe
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« Reply #3 on: June 12, 2014, 11:01:28 PM »
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Oh, it's a Bayer array...it's just a non-standard Bayer array. But as far as I know, yes, what I said holds...the only camera I'm aware of where the original raw file is processed to open in ACR/LR are Sigma cameras (whose sensors are NOT any sort of Bayer array).
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dmward
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« Reply #4 on: June 13, 2014, 10:23:17 PM »
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OK,
Thanks.
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dmward
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« Reply #5 on: June 14, 2014, 09:22:45 AM »
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How does DNG handle a newer camera model raw file so it can be opened by earlier version of Lightroom what doesn't support the camera manufacturer's format?
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AFairley
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« Reply #6 on: June 14, 2014, 10:16:56 AM »
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I have found that PhotoNinja does not open Fujifilm X camera RAWs that have been converted to DNG, but based on Jeff's post, that would seem to be a file-reading limitation rather tan the RAW data having been altered in the conversion?
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digitaldog
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« Reply #7 on: June 14, 2014, 11:35:01 AM »
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How does DNG handle a newer camera model raw file so it can be opened by earlier version of Lightroom what doesn't support the camera manufacturer's format?
The converter itself has to be updated to understand this newer proprietary raw format. Once it understands it, a DNG is created. Then older versions of LR understand that standard DNG format. Think of it like a newer raw converter rendering a JPEG fron this newer raw camera file. That JPEG being an open and understood format could be opened in a really old copy of Photoshop or any other app that understands what a JPEG is.
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Andrew Rodney
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Sterling22
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« Reply #8 on: June 14, 2014, 09:01:34 PM »
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So, in practical terms, I can fiddle around with a Fuji Raw file in Lightroom, then if I'm not happy with it, I could open that Raw file in Photo Ninja and start fresh with Photo Ninja's demosaicing?
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Schewe
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« Reply #9 on: June 14, 2014, 09:57:25 PM »
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So, in practical terms, I can fiddle around with a Fuji Raw file in Lightroom, then if I'm not happy with it, I could open that Raw file in Photo Ninja and start fresh with Photo Ninja's demosaicing?

Yep...
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digitaldog
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« Reply #10 on: June 14, 2014, 10:20:05 PM »
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So, in practical terms, I can fiddle around with a Fuji Raw file in Lightroom, then if I'm not happy with it, I could open that Raw file in Photo Ninja and start fresh with Photo Ninja's demosaicing?
Correct.
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Andrew Rodney
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Sterling22
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« Reply #11 on: June 14, 2014, 10:36:16 PM »
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Thank you gents.
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Keith Reeder
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« Reply #12 on: June 15, 2014, 04:09:38 AM »
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So, in practical terms, I can fiddle around with a Fuji Raw file in Lightroom, then if I'm not happy with it, I could open that Raw file in Photo Ninja and start fresh with Photo Ninja's demosaicing?

Note that this is true of any Raw file/converter combination. The Raw files are never changed (ignoring possible Exif/metadata changes) at conversion - this is the essence of "non destructive" Raw processing - with the output always being in effect a copy of the converted image.

So you can move from converter to converter ad infinitum with the same Raw file, and in terms of the image information in the file, you're starting from a "virgin" file each time.

This is why an (arguably imperfect) analogy is often drawn between Raw files and film negatives.
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Keith Reeder
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dmward
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« Reply #13 on: June 19, 2014, 12:35:58 AM »
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Thanks guys.
This is, for me, a useful explanation of how raw data, collected by a camera that is newer than the processing software, can be given access to the data by creating a container for the data that is understood by the older software.

I think I understand how a non-standard Bayer pattern, such as the Fujifilm X-Trans, can be packaged in the DNG wrapper in such a way that a raw converter that is unaware of the X-Trans format can still extract the data.

A clear explanation would held :-)

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