DNG and MacOS compatibility - RAW Shooting and Processing - CHDK Forum
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DNG and MacOS compatibility

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Offline ldu

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DNG and MacOS compatibility
« on: 06 / November / 2009, 06:55:05 »
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Offline ewavr

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Re: DNG and MacOS compatibility
« Reply #1 on: 06 / November / 2009, 07:17:23 »
Quote from: ldu on 06 / November / 2009, 06:55:05
what is difference between CHDK DNG and Adobe DNG?

Main difference is: CHDK DNG is 10- or 12-bit file (depends on camera model), Adobe DNG converter produces 16-bit DNG file. Some software cannot understand 10(12)-bit files.

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(Also, it is strange :
- direct dng from camera gives a 9,3Mo file
- reprocessing with DNG converter gives a 5,9 Mo file )
Because Adobe DNG converter uses lossless DNG compression.
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Offline ldu

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Re: DNG and MacOS compatibility
« Reply #2 on: 06 / November / 2009, 10:57:57 »
thank you for answer.
for a better integration with MacOs, is there a chance to obtain directly a 16-bit DNG file with a next release ? or a parameter to choose 10-/12 bit ou 16 ?
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Offline vit40

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Re: DNG and MacOS compatibility
« Reply #3 on: 06 / November / 2009, 16:35:35 »
I don't se a benefit of saving 16 bit dng-s in camera. It will occupy more space on the card and saving will last even longer ...
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Offline reyalp

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Re: DNG and MacOS compatibility
« Reply #4 on: 06 / November / 2009, 16:42:37 »
In addition ot what vit40 said, the 10/12 bit format used by CHDK is in the DNG standard. If your DNG software doesn't fully support the standard, you should take it up with the person responsible for that software.
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Offline ldu

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Re: DNG and MacOS compatibility
« Reply #5 on: 07 / November / 2009, 05:12:55 »
You're right.
But not sure Apple will modify the softwares in a near future !
Also, I thing it is easier to have an option within CHDK...
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Offline reyalp

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Re: DNG and MacOS compatibility
« Reply #6 on: 07 / November / 2009, 16:38:15 »
Quote from: ldu on 07 / November / 2009, 05:12:55
Also, I thing it is easier to have an option within CHDK...
This would almost certainly more than double the time required to capture DNG, and increase the size in camera DNG by about 30%-50%. I certainly won't be investing any time to implement this just to work around a vendor who CBA to support the standard.

Since you already have a tool that converts to a format Apple understands, I suggest you use it. Adding a batch conversion to your workflow should not be a major problem.
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Offline cppasm

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Re: DNG and MacOS compatibility
« Reply #7 on: 18 / November / 2009, 10:09:38 »
Quote from: ldu on 06 / November / 2009, 06:55:05
what is difference between CHDK DNG and Adobe DNG?
The main difference is that CHDK DNG is NOT following DNG specification.
It uses Adobe PageMaker extension SubIFDs (tag 0x14A) instead of normal IFD linking.
http://www.awaresystems.be/imaging/tiff/tifftags/subifds.html
This need to be fixed, and not so hard to do.
I don't know why this extension is used.

But before fixing something we need to check am I write or not.
If you are interested, I can upload fixed DNG for you to test it with your software.
There is small possibility that ewavr is write, and programs just don't understand 10bit and 12bit DNG.
But I don't really think so.
« Last Edit: 18 / November / 2009, 10:16:59 by cppasm »
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Offline ewavr

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Re: DNG and MacOS compatibility
« Reply #8 on: 18 / November / 2009, 10:19:25 »
Quote from: cppasm on 18 / November / 2009, 10:09:38
The main difference is that CHDK DNG is NOT following DNG specification.
It uses Adobe PageMaker extension SubIFDs (tag 0x14A) instead of normal IFD linking.

DNG specification 1.2.0.0:
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DNG recommends the use of SubIFD trees, as described in the TIFF-EP specification. SubIFD chains are not supported.
If I use IFD linking, dng_validate gives me a warning (I don't remember which). If I use SubIFD, no warnings.
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Offline cppasm

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Re: DNG and MacOS compatibility
« Reply #9 on: 18 / November / 2009, 10:37:58 »
Quote from: ewavr on 18 / November / 2009, 10:19:25
If I use IFD linking, dng_validate gives me a warning (I don't remember which). If I use SubIFD, no warnings.
I don't see any warnings with my dng_validate...
And by the way - we write DNG version 1.1.0.0 to DNG header, and SubIFDs is not in this specification.
Second reason - chaining is just a subset of tree (tree without branches), it can't be wrong.
Third reason - my Adobe DNG Converter dont write SubIFD tags, maybe newer will, I dont know.
Well, in my own build I have completely removed thumbnail because of bad quality - so this is not problem for me :)

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There may be more than one IFD in a TIFF 6.0 file. Each IFD defines a subfile. One potential use of subfiles in
TIFF 6.0 is to describe related images, such as the pages of a facsimile transmission. A Baseline TIFF 6.0 reader
is not required to read any IFDs beyond the first one.
This is exactly what programs are doing according to description above.
They show thumbnail (first IFD), but don't read full-sized image data.

Well, to be sure - we need examples of working (converted) and non working (CHDK) DNG files to compare.
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