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Difference between Canon CRW and CHDK CRW?

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Difference between Canon CRW and CHDK CRW?
« on: 16 / May / 2008, 11:33:03 »
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Question I have not found an answer to: What is difference between Canon CRW and CHDK CRW?(did find that CHDK CRW do not have an EXIF file).

Thanks

Gene

Re: Difference between Canon CRW and CHDK CRW?
« Reply #1 on: 16 / May / 2008, 11:36:26 »

Re: Difference between Canon CRW and CHDK CRW?
« Reply #2 on: 16 / May / 2008, 11:40:26 »
Forgot to also add this Canon CRW info I found at  The Canon RAW (CRW) File Format
"The Canon RAW (CRW) File Format  This is a description of the Canon CRW file format. CRW files are written in Camera Image File Format (CIFF). The original Canon CIFF documentation can be downloaded from Index of /ciff (which I finally discovered after writing this document!). Note that Canon uses two different RAW formats, and some camera models produce CR2 instead of CRW files. The CR2 files use a TIFF format, which is different than the CRW CIFF format documented here.
Comments about the CRW Format  The Canon CRW file format is a joy to work with. It has a structure that is fundamentally similar to TIFF, with directories that point to data within the file. But a major improvement over TIFF is that the offsets are not absolute, they are relative to the start of the data block for each directory. This allows subdirectories within a file to be moved or copied to another file without having to adjust the offsets, which is fantastic because it means that rewriter software doesn't have to understand the complete format in order to be able to successfully rewrite the file.

Also, the data comes before the directories in the file, which is the natural way to write information and minimizes the amount memory needed to buffer the data (unlike the EXIF standard which is the reverse).

A short rant about TIFF inadequacies: TIFF format on the other hand, really sucks in comparison (this includes JPEG too, since JPEG uses TIFF format to store the EXIF information). The main problems are the use of absolute offsets and the ambiguity between integers and pointers (such as those used for custom IFD's). Because absolute offsets require adjusting whenever anything is moved in the file, the format of ALL contained data structures must be understood to properly edit the file. This results in an impossible situation when presented with undocumented custom structures like those used in the maker notes written by modern digital cameras. This is why it is so common for image editors to either scramble the maker notes or discard them completely. The official TIFF recommendation is to discard unknown information when rewriting the image (as Photoshop does), but for many, including myself, this option is simply unacceptable.

The bottom line is that rewriting a Canon CRW file is about 20 times easier, and much less prone to errors than rewriting a TIFF or JPEG."

Gene

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Offline RaduP

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Re: Difference between Canon CRW and CHDK CRW?
« Reply #3 on: 17 / May / 2008, 21:42:05 »
I don't think there are many differences (a program that can read my Rebel 300D RAW files can read the CHDK RAW files too).
You see, CHDK doesn't have it's own RAW format, it just saves it from the camera (the camera provides that by itself). So I guess it would be safe to assume that the Canon camers use the same basic raw format.

Only things that are different is that the 'chdk raw' doesn't have some data such as the white balace and EXIF data. I would also guess that only 10 bpp is used for the P&S camers.


Re: Difference between Canon CRW and CHDK CRW?
« Reply #4 on: 14 / June / 2008, 03:47:04 »
dpp that comes with rebel series now do not support chdk raw ... can we make it a uniform instead somehow ???

silly to use different software for each camera ...

thanks

I don't think there are many differences (a program that can read my Rebel 300D RAW files can read the CHDK RAW files too).
You see, CHDK doesn't have it's own RAW format, it just saves it from the camera (the camera provides that by itself). So I guess it would be safe to assume that the Canon camers use the same basic raw format.

Only things that are different is that the 'chdk raw' doesn't have some data such as the white balace and EXIF data. I would also guess that only 10 bpp is used for the P&S camers.

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Offline dzsemx

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Re: Difference between Canon CRW and CHDK CRW?
« Reply #5 on: 14 / June / 2008, 08:33:17 »
@RaduP
raw produced by chdk is really "raw"... it has no header and it doesn't contain any information about the camera and the data is not compressed in any way.
chdk simply writes the raw buffer to a file on the memorycard
so it's not recognized directly by many raw-processing software
exception is RAWTherapee which handles direcly chdk raws
« Last Edit: 14 / June / 2008, 08:39:56 by dzsemx »

Re: Difference between Canon CRW and CHDK CRW?
« Reply #6 on: 15 / June / 2008, 15:10:42 »
Hi all
I am from Austria, sorry for my English. Working with CHDK I tested the raw-output of my Ixus50. My standardphotoprogramm - I use FixFoto - works verry well with the raws saved on the card.
It also works well with the raws of my Canon 20D.
I don`t see any differences in my workflow.

Thanks for the development of CHDK. I am so happy.

greets
Peter

Re: Difference between Canon CRW and CHDK CRW?
« Reply #7 on: 15 / June / 2008, 17:32:00 »
@RaduP
raw produced by chdk is really "raw"... it has no header and it doesn't contain any information about the camera and the data is not compressed in any way.
chdk simply writes the raw buffer to a file on the memorycard
so it's not recognized directly by many raw-processing software
exception is RAWTherapee which handles direcly chdk raws


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Offline dzsemx

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Re: Difference between Canon CRW and CHDK CRW?
« Reply #8 on: 15 / June / 2008, 18:43:37 »
Hi all
I am from Austria, sorry for my English. Working with CHDK I tested the raw-output of my Ixus50. My standardphotoprogramm - I use FixFoto - works verry well with the raws saved on the card.
It also works well with the raws of my Canon 20D.
I don`t see any differences in my workflow.

it really works and it's fast
only works for my a630raws, a650 raws are not supported
so there is another exception
« Last Edit: 15 / June / 2008, 19:01:10 by dzsemx »

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Offline RaduP

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Re: Difference between Canon CRW and CHDK CRW?
« Reply #9 on: 21 / June / 2008, 23:05:09 »
I am using UFraw, and it works great with my A570 CHDK raw files. Not sure if it works with other cameras supposrted by CHDK, but I think it's worth giving it a try, it's a relaly nice and free program.

 

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