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Backing up RAW files: DNG or CRW

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Offline cryptomega

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Backing up RAW files: DNG or CRW
« on: 29 / June / 2008, 01:32:21 »
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Hello

I am trying to decide on a solid scheme to organize and backup my RAW files.  Just right now I am not sure if I should keep the original CRW file the camera saves, or the DNG file it is converted too.  It would obviously be much more useful to save it as a unprocessed DNG, since I can preview it or load it with most software.  The CRW files have to be converted first though.

Is there any other technical reason I should keep the CRW files?

Thanks
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Offline PhyrePhoX

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Re: Backing up RAW files: DNG or CRW
« Reply #1 on: 29 / June / 2008, 05:57:26 »
no, no reason at all. keep the dngs. dng will probably last 100 years, whereas the crw files arent really supported by major apps right now.
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Offline ewavr

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Re: Backing up RAW files: DNG or CRW
« Reply #2 on: 29 / June / 2008, 06:56:05 »
My opinion: crw (as original images) + jpeg + converter (maybe even in 100 years dcraw.c can be compiled  :) ).
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Offline fe50

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Re: Backing up RAW files: DNG or CRW
« Reply #3 on: 29 / June / 2008, 07:50:16 »
cryptomega,

and don't forget either to have the Exif data in your DNG (when converting it) or to save the corresponding JPEG because the RAW file does not contain this data, it's only stored in the JPEG file...

To save space you can compress the CRW's e.g. with 7-Zip, in ultra compress mode the size is reduced to ~ 70%, or use the compress-DNG setting in DNG4PS-2 when converting to DNG (without losing quality, too)...

For rare shots storing the JPEG file additionally is also a good idea: for later comparison between the "Canon result" (=original) of a pic and the result of your imaging software - the software will often change the next 100 years, so you can always have a look back...
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Offline cryptomega

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Re: Backing up RAW files: DNG or CRW
« Reply #4 on: 02 / July / 2008, 16:38:49 »
Although I was leaning towards deleting the CRW files, I might just compress them and hold onto them a bit. That way if dcraw or other software adds support, I can compare the results. I'll also throw in the origianal JPEGs and the converter into each zip file, so I won't have to hunt it down if I ever need to recover the RAWs.

When I have some spare time, I'll put togethor an autohotkey script to automatically copy, convert, and archive images straight from the memory card. That would make my life much easier.

Thanks for your replies!
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Offline oversky

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Re: Backing up RAW files: DNG or CRW
« Reply #5 on: 03 / July / 2008, 21:53:39 »
The DNG should have all information in the raw file + the EXIF from jpeg. The only concern is that dng4ps may not have good color matrix when you tranlate raw to DNG. Can we change the color matrix later?
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Offline cyril42e

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Re: Backing up RAW files: DNG or CRW
« Reply #6 on: 03 / July / 2008, 22:51:38 »
Yes, there is a program called dngsetmatrix, see New project: camera color profile calculation.

But changing the matrix takes some time, so I don't know if there is just the original CRW data on 16 bits plus the color matrix, or the converted raw data and the matrix that gave these data from CRW, in order to be able to find back the original CRW data and change the matrix...
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Offline yg2007

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Re: Backing up RAW files: DNG or CRW
« Reply #7 on: 05 / July / 2008, 11:50:46 »
DNG deteriorated the original file by adding some annoying blue noise.  For best image quality, I recommended CRW.
« Last Edit: 05 / July / 2008, 11:54:53 by yg2007 »
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Offline PS

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Re: Backing up RAW files: DNG or CRW
« Reply #8 on: 05 / July / 2008, 12:44:18 »
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Offline user1

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Re: Backing up RAW files: DNG or CRW
« Reply #9 on: 05 / July / 2008, 12:56:59 »
Quote from: PS on 05 / July / 2008, 12:44:18
But personally I keep straight out of camera CRW (never bothered to convert it to other formats).
BTW 2616x1960x10bpp = 6 409 200 bytes (for 5MP camera) but it takes 6 573 120 bytes of space, so what are those 163 920 bytes?

Those 163 920 cropped during RAW conversion :)

For A610, RAW is 2672 x 1968.
2672*1968*10/8=6 573 120
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