ExifTool Forum

[Originally posted by gekap on 2009-06-11 15:48:58-07]

I use Jalbum to publish my pictures to the web, and I want to have the information of the used lens displayed in the EXIF-data. I'm most using Olympus DSLRs to take my photos, and Olympus stores the lens-information in the vendor-specific Makernotes EXIF field "LensType" (TagID 0x0201). Because Jalbum is using a java-library to extract the metadata of the pictures which does not support to read this vendor-specific field I have written a script which loops through my JPGs, does some checks (is the JPGs taken by a Olympus DSLR by reading the fields "Make" and "Model", is the Makernote field "LensType" not empty and so on) and copies then the content of this vendor specific field "LensType" to the standard-EXIF-field "Lens" (TagID 0xfdea) using exiftool (bye the way: many thanks for that perfect tool!!!). That all works perfect, but there is a issue: when I display the lens-information in Jalbum I can see a additional "Lens: " beetween the field-descriptor (which is inserted by Jalbum) and the value of the field "Lens". So I contacted the developer of Jalbum to fix this "bug", but he says, that "Lens: " is part of the value in the JPGs, and somehow he is right: when I open one of my modified JPGs with a plain text editor and search for the lens-infos, I can find this string
what's confusing for me.

then I started to try a couple of tools which can read EXIF-content, and here are the results (some of the tools are in german version, that's why you can sometimes see "Objektiv:" as field descriptor which is the german word for "lens"):

exiftool
Photoshop CS4
Kuso Exif Viewer
Jalbum
EXIF Viewer by KMK
so I can see that not only Jalbum doesn't display this EXIF field in a correct way, other tools have troubles, too - but some application (i.e. Photoshop) are displaying the field correct!

my conclusion is, that it's "normal" that the tag-value 0xfdea starts with a "Lens: ", and that's not a bug of Exiftool (with which i've written that EXIF-field), but an application which will extract this value has to strip off the starting "Lens: ", and maybe use it as field descriptor... Am I right?

can anyone give me a hint where I can find information or documentation in the Internet how to handle it correct to read the "Lens"-field of a JPGs (or some related EXIF fields), or maybe can anyone explain that in short form, especially the fact that the lens-information inside the field with ID 0xfdea starts with a "Lens: , and if this is "normal" or the rule... because I need arguments to tell the developer of Jalbum that there is a issue in the metadata extraction library of Jalbum causing that an additional "Lens: " is displayed, and it is not an issue with my pictures or Exiftool!

many thanks for helping!

Gerald

[Originally posted by exiftool on 2009-06-11 16:04:11-07]

Hi Gerald,

I saw your post in the
Jalbum
forum.

The tag you are using (EXIF tags in the rang 0xfde8-0xfe58) are private
photoshop camera raw tags that may not be interpreted properly by
some software.  The values are stored as a string, with a leading tag
name followed by a colon.  Software must know about these private tags
to properly strip off the tag name from the value.  ExifTool does this.
You can always use the -v3 option to see exactly what it
stored in the file if you have any question.

I wouldn't consider this a Jalbum bug, but simply that Jalbum lacks support
for these private photoshop tags.

- Phil

[Originally posted by gekap on 2009-06-11 16:26:13-07]

Hi Phil,

thanks for the quick response! O.k., I didn't know that this tags are "private photoshop". In my opinion the cause of displaying this field not correct is inside Jalbum: when the metadata extraction library of Jalbum can read this field it should know about how to correct handle the value of it - but you can see that from another point of view... :-) (maybe you have seen it: I've currently a workaround in place, which is stripping out the string "Lens: " of the variable which comes from Jalbum through when it's getting processed by the skin...)

can you recommend me the use of another, not vendor specific EXIF-field to store the lens-info inside a JPG, maybe one that is "more common", and is probably supported from a wider range of tools?

thanks for helping

- Gerald

[Originally posted by exiftool on 2009-06-11 17:10:14-07]

Hi Gerald,

There is really nothing in EXIF that would satisfy this.  The best place
for this would be in the XMP "Lens" tag, which is part of the XMP
specification.  The  only problem with this is that XMP support may
not be as universal as you require.  (I have no idea if Jalbum supports
XMP.)

- Phil