New tool to view metadata from image files

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John Francis - 18 Jan 2007 17:23 GMT

Ever since I got my *ist D I've been digging around inside the image files
to try and understand just what is being stored there. I've decided it's
about time to share this information with a wider body of DSLR users.

Please take a look at

http://www.pdml.us/raw/index.html

for a description of what I've found out about the overall format of
Pentax image files, and what I've managed to deduce about the
metadata stored in the Pentax MakerNote fields. There's also a link
to the latest incarnation of the utility I wrote to extract this data

The tool will be of most use to owners of Pentax cameras (because those
are the only files where I decode any of the MakerNote information), but
it will at least show you all the EXIF information from JPEGs from most
cameras, from Adobe DNG files, and from any TIFF/EP structured RAW file
(which includes most RAW formats from Canon, Nikon, etc.)

Enjoy! If you discover anything new and interesting, or can fill in any
of the blanks in the information I have collected, please let me know.

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Ken Lucke - 18 Jan 2007 17:44 GMT

> Ever since I got my *ist D I've been digging around inside the image files
> to try and understand just what is being stored there. I've decided it's
[quoted text clipped - 17 lines]
> Enjoy! If you discover anything new and interesting, or can fill in any
> of the blanks in the information I have collected, please let me know.

Uhm, ever heard of ExifTool?

http://www.sno.phy.queensu.ca/~phil/exiftool/index.html

http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Pentax.html

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John Francis - 18 Jan 2007 18:16 GMT

>Uhm, ever heard of ExifTool?
>
>http://www.sno.phy.queensu.ca/~phil/exiftool/index.html
>
>http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Pentax.html

Yes, of course I've heard of ExifTool. In fact some of the
information about Pentax TagNames in ExifTool comes from me.
But at the time I wrote ShowTags there wasn't a stand-alone
Windows (or Mac) executable version of ExifTool; that's
only been added very recently.

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Ken Lucke - 18 Jan 2007 18:22 GMT

> >Uhm, ever heard of ExifTool?
> >
[quoted text clipped - 7 lines]
> Windows (or Mac) executable version of ExifTool; that's
> only been added very recently.

OK, it just looked to me as if you were reinventing the wheel, and I
wannted to save you some trouble.

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John Francis - 18 Jan 2007 20:03 GMT

>> >Uhm, ever heard of ExifTool?
>> >
[quoted text clipped - 10 lines]
>OK, it just looked to me as if you were reinventing the wheel, and I
>wannted to save you some trouble.

Thanks for that. In fact I'll still continue to use ShowTags; the
output is optimised for what I want, and it's handy to be able to
stop at a breakpoint and peer around inside the data structures.
I also use ShowTags as a development vehicle for the routines that
pull apart the various image files, and which I use in a couple of
more focussed analysis utilities.

But it's of rather less use to the general camera user; I've added
a link to ExifTool from my ShowTags page, and suggested it might
be a better utility for most people.

One thing ShowTags does, at present, which ExifTool does not, is
to extract Pentax MakerNote data from a K10D in-camera DNG file.
I've passed the relevant details on to Phil, and fully expect
the capability to show up in ExifTool in the near future.

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Barry Pearson - 19 Jan 2007 00:08 GMT

> Ever since I got my *ist D I've been digging around inside the image files
> to try and understand just what is being stored there. I've decided it's
> about time to share this information with a wider body of DSLR users.

[snip]

I downloaded ShowTags and started to use it 3 days ago. (I think I got
a link in DPReview?) Thanks for that.

Do you have dng_validate.exe from the DNG SDK? It is a TIFF/EP analyser
with an emphasis on DNG. One thing it does is provide an interpretation
of some of the values in TIFF tags. If you ever want to turn some of
your numbers into names, it might be a good place to start.

Comparisons:

ShowTags:
Main IFD: BaselineSharpness 50732 5 1 @0x00001D3A
Main IFD: LinearResponseLimit 50734 5 1 @0x00001D42
Main IFD: <UNKNOWN TAG 50736> 50736 5 4 @0x00001D4A
Main IFD: ShadowScale 50739 5 1 @0x00001D6A

dng_validate:
BaselineSharpness: 1.33
LinearResponseLimit: 1.00
LensInfo: 16.0-45.0 mm f/4.0
ShadowScale: 1.0000

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Barry Pearson
http://www.barrypearson.co.uk/photography/

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John Francis - 19 Jan 2007 00:23 GMT

>> Ever since I got my *ist D I've been digging around inside the image files
>> to try and understand just what is being stored there. I've decided it's
[quoted text clipped - 3 lines]
>I downloaded ShowTags and started to use it 3 days ago. (I think I got
>a link in DPReview?) Thanks for that.

I tried to notify you by private email sent to the address you give in
your profile in the Adobe DNG forums (photography@barrypearson.co.uk),
but that address no longer seems to be accepting mail :-(

>Do you have dng_validate.exe from the DNG SDK? It is a TIFF/EP analyser
>with an emphasis on DNG. One thing it does is provide an interpretation
>of some of the values in TIFF tags. If you ever want to turn some of
>your numbers into names, it might be a good place to start.

I've got the DNG SDK, but haven't done all that much with it.
I'm probably not going to do much more with ShowTags; now that
Phil Harvey has released Windows & Mac standalone versions of
ExifTool there's less need for yet another tag dumping tool.

>Comparisons:
>
[quoted text clipped - 9 lines]
>LensInfo: 16.0-45.0 mm f/4.0
>ShadowScale: 1.0000

Again, I'll probable leave most of the interpretation, etc.,
to ExifTool. BTW, the current version of ShowTags does at
least print out the value of rationals. It still wouldn't
interpret that LensInfo tag, though (I might just fix that ...)

Where did you get a DNG file with a LensInfo tag? ACR 4 ?

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Barry Pearson - 19 Jan 2007 09:10 GMT

[snip]

> Where did you get a DNG file with a LensInfo tag? ACR 4 ?

I have a number of them. (The tag was in DNG version 1.0.0.0). That DNG
was dated 1 August 2006, so I guess it was the 3.4 DNG Converter. (The
Ricoh GRD puts that tag into its own DNG).

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Barry Pearson
http://www.barrypearson.co.uk/photography/

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DoN. Nichols - 19 Jan 2007 04:21 GMT

According to John Francis <johnf@panix.com>:

> Ever since I got my *ist D I've been digging around inside the image files
> to try and understand just what is being stored there. I've decided it's
[quoted text clipped - 3 lines]
>
> http://www.pdml.us/raw/index.html

    DO you have a Makefile for the program source? What are the
library dependencies? I seem to be having difficulties compiling it
using gcc on Sun Solaris 10 systems.

    I note that you have it listed as compiling on OS-X, so other
unix systems *should* work.

    I already use exiftool, but any other program for examining the
interior of image files is a nice thing to have.

    Thanks,
        DoN.

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John Francis - 19 Jan 2007 08:06 GMT

>According to John Francis <johnf@panix.com>:
>> Ever since I got my *ist D I've been digging around inside the image files
[quoted text clipped - 11 lines]
> I note that you have it listed as compiling on OS-X, so other
>unix systems *should* work.

I just use: g++ -Wno-deprecated -o ShowTags ShowTags.cpp TiffSubs.cpp

That works for me on Linux, and I believe that's what was used on OS-X

> I already use exiftool, but any other program for examining the
>interior of image files is a nice thing to have.

ExifTool is significantly better on interpreting content; ShowTags gives
rather more information on structure (file offsets, tag datatypes, etc.)

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DoN. Nichols - 20 Jan 2007 06:10 GMT

According to John Francis <johnf@panix.com>:

> >According to John Francis <johnf@panix.com>:
> >> Ever since I got my *ist D I've been digging around inside the image files
[quoted text clipped - 15 lines]
>
> That works for me on Linux, and I believe that's what was used on OS-X

======================================================================
Fuego:csu 1:01:13 # g++ -Wno-deprecated -o ShowTags ShowTags.cpp TiffSubs.cpp
TiffSubs.h: In destructor 'TIFFTag::~TIFFTag()':
TiffSubs.h:35: warning: deleting 'TIFFVoid*' is undefined
TiffSubs.h: In destructor 'TIFFTag::~TIFFTag()':
TiffSubs.h:35: warning: deleting 'TIFFVoid*' is undefined
TiffSubs.cpp: In member function 'TIFFTag& TIFFTag::operator=(const TIFFTag&)':
TiffSubs.cpp:36: warning: deleting 'TIFFVoid*' is undefined
======================================================================

    However -- it seems to work -- since those are just warnings,
not errors which will halt the compilation.

    Now -- I get information when running it on a D70 image file.
But I don't see any easy way to determine what command-line options it
may have. (Does it have *any*?) I tried:

ShowTags -h
ShowTags --help
ShowTags -help
ShowTags -\?

    All the ways that are common to provoke a program into issuing a
"usage" message. I simply get something like the following:

======================================================================
Fuego:csu 1:05:32 # ShowTags --help
Processing --help

======================================================================

> > I already use exiftool, but any other program for examining the
> >interior of image files is a nice thing to have.
>
> ExifTool is significantly better on interpreting content; ShowTags gives
> rather more information on structure (file offsets, tag datatypes, etc.)

    O.K.

    Thanks,
        DoN.

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John Francis - 20 Jan 2007 06:53 GMT

>According to John Francis <johnf@panix.com>:
>> >According to John Francis <johnf@panix.com>:
[quoted text clipped - 29 lines]
> However -- it seems to work -- since those are just warnings,
>not errors which will halt the compilation.

That's right. GNU C++ seems to want me to cast a void* to something
else before deleting it. But, as you say, it's just a warning.

> Now -- I get information when running it on a D70 image file.
>But I don't see any easy way to determine what command-line options it
>may have. (Does it have *any*?)

No. No options - it just dumps the file structure and the tags in a
form I happen to find useful when digging around inside the files.

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DoN. Nichols - 21 Jan 2007 03:22 GMT

According to John Francis <johnf@panix.com>:

[ ... ]

> > However -- it seems to work -- since those are just warnings,
> >not errors which will halt the compilation.
>
> That's right. GNU C++ seems to want me to cast a void* to something
> else before deleting it. But, as you say, it's just a warning.

O.K. I'm familiar with C, but do very little with C++ and its
variants.

> > Now -- I get information when running it on a D70 image file.
> >But I don't see any easy way to determine what command-line options it
> >may have. (Does it have *any*?)
>
> No. No options - it just dumps the file structure and the tags in a
> form I happen to find useful when digging around inside the files.

    O.K. Thanks. At least I'm not missing anything which should be
obvious for listing options.

    Thanks,
        DoN.

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