DNG compatibility for ACR (A720 vs SX1) - RAW Shooting and Processing - CHDK Forum
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DNG compatibility for ACR (A720 vs SX1)

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Offline dohduhdah

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DNG compatibility for ACR (A720 vs SX1)
« on: 13 / July / 2009, 22:21:37 »
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Hi.
Does anyone have any explanation why the DNG files produced by CHDK on a Canon Powershot A720 are read without problems by Adobe Camera Raw, while DNG files produced by CHDK on a Canon Powershot SX1 aren't recognized by ACR?
Is this likely to be resolved in the near future with an update of ACR or an update of CHDK?

Kind regards and thanks in advance for any suggestions, Niek
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Offline dohduhdah

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Re: DNG compatibility for ACR (A720 vs SX1)
« Reply #1 on: 14 / July / 2009, 15:14:34 »

For what it's worth, I've been comparing the DNG files created by CHDK on both of my Canon cameras (the powershot sx1 and the powershot a720) to see if I can figure out why Adobe Camera Raw rejects one, while accepting the other:
http://www.ibbu.nl/~nsprakel/winhex1.jpg

With photoshop, you can select the data on the right and superimpose it on the data on the left in difference mode, to find
the differences between both files. I've blurred those differences and superimposed it in a blue color on the left side, to
highlight the differences:
http://www.ibbu.nl/~nsprakel/winhex2.jpg

In winhex1.jpg, you can see a small marked section of 8 bytes from offset 457 to 45E (hexadecimal) in the header of both DNG files. It turns out that if you modify the DNG to ensure the first and last byte match, the DNG will be recognized by ACR, but the thumbnail is not displayed properly in the windows explorer.
In this specific case, that means I have to change the first and last byte (of the marked sequence of 8 bytes) in the file CRW_0880.DNG:
0E -> 0C (at offset 457)
18 -> 08 (at offset 45E)

When those two bytes are modified, the DNG file can be loaded in ACR. So apparently, it's a simple issue with the header of the DNG file.

Maybe someone else can figure out how to get the thumbnail to display properly.  :-)
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Offline user1

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Re: DNG compatibility for ACR (A720 vs SX1)
« Reply #2 on: 14 / July / 2009, 15:47:21 »
Quote from: dohduhdah on 13 / July / 2009, 22:21:37
Does anyone have any explanation why the DNG files produced by CHDK on a Canon Powershot A720 are read without problems by Adobe Camera Raw, while DNG files produced by CHDK on a Canon Powershot SX1 aren't recognized by ACR?
It would be useful to see DNG from SX1.

Hint: use dng_validate tool from Adobe DNG SDK to validate dng files.
« Last Edit: 14 / July / 2009, 15:49:32 by user1 »
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Offline dohduhdah

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Re: DNG compatibility for ACR (A720 vs SX1)
« Reply #3 on: 14 / July / 2009, 16:24:08 »
Quote from: user1 on 14 / July / 2009, 15:47:21
Quote from: dohduhdah on 13 / July / 2009, 22:21:37
Does anyone have any explanation why the DNG files produced by CHDK on a Canon Powershot A720 are read without problems by Adobe Camera Raw, while DNG files produced by CHDK on a Canon Powershot SX1 aren't recognized by ACR?
It would be useful to see DNG from SX1.

Hint: use dng_validate tool from Adobe DNG SDK to validate dng files.

Here is a DNG from the SX1:

http://www.ibbu.nl/~nsprakel/CRW_0881.DNG
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Offline dohduhdah

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Re: DNG compatibility for ACR (A720 vs SX1)
« Reply #4 on: 14 / July / 2009, 17:07:04 »
Quote from: user1 on 14 / July / 2009, 15:47:21
Quote from: dohduhdah on 13 / July / 2009, 22:21:37
Does anyone have any explanation why the DNG files produced by CHDK on a Canon Powershot A720 are read without problems by Adobe Camera Raw, while DNG files produced by CHDK on a Canon Powershot SX1 aren't recognized by ACR?
It would be useful to see DNG from SX1.

Hint: use dng_validate tool from Adobe DNG SDK to validate dng files.

dng_validate says "*** Error: Invalid DefaultCropSize ***"
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Offline vit40

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Re: DNG compatibility for ACR (A720 vs SX1)
« Reply #5 on: 14 / July / 2009, 17:58:46 »
Crop area (defined by appropriate tag) can't fit into active area (defined by other tag). Active area should be enlarged by one pixel in x and y direction

try this

exiftool -activearea="24 344 2760 3992"   <dng_filename>

In my case, it did the trick

Someone correct these values in the code please

BTW: isn't it better to use cr2 file right from the camera ? It's compressed and smaller than uncompressed dng
« Last Edit: 14 / July / 2009, 18:06:52 by vit40 »
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Offline user1

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Re: DNG compatibility for ACR (A720 vs SX1)
« Reply #6 on: 14 / July / 2009, 18:01:00 »
Indeed, dng_validate reports about you file:
Code: [Select]
ActiveArea: T = 24 L = 344 B = 2759 R = 3991

Maybe active area is too small.

Here is dng file produced from SX1's CR2 by Abode DNG converter:

Code: [Select]
ActiveArea: T = 12 L = 192 B = 2772 R = 4152

Maybe CHDK setting (active area) must be corrected.
« Last Edit: 14 / July / 2009, 18:02:51 by user1 »
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Offline vit40

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Re: DNG compatibility for ACR (A720 vs SX1)
« Reply #7 on: 14 / July / 2009, 18:11:15 »
It's safe to use tag values from dng, produced by DNG converter (although I didn't try, as I don't have any cr2 from sx1). Besides active area, you can also use crop area (slightly larger, I suppose), crop origin, color matrices etc ...
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Offline user1

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Re: DNG compatibility for ACR (A720 vs SX1)
« Reply #8 on: 14 / July / 2009, 18:35:39 »
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Offline dohduhdah

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Re: DNG compatibility for ACR (A720 vs SX1)
« Reply #9 on: 14 / July / 2009, 18:54:09 »
Quote from: vit40 on 14 / July / 2009, 18:11:15
It's safe to use tag values from dng, produced by DNG converter (although I didn't try, as I don't have any cr2 from sx1). Besides active area, you can also use crop area (slightly larger, I suppose), crop origin, color matrices etc ...


Here is a CR2 from the SX1:

http://www.ibbu.nl/~nsprakel/IMG_0879.CR2
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