ExifTool Forum

[Originally posted by steveste on 2006-01-05 17:18:57-08]

I haven't found a way to modify a file so that in Windows XP the Date Picture Taken can be changed. I hoped this was read some way via EXIF.

In fact, when I write EXIF data, and then view the picture in XnView - it doesn't display an EXIF tag (which it does when I view a digital photo). Why would that be? Is there some EXIF flag that ExifTool doesn't write?

Thanks

[Originally posted by exiftool on 2006-01-05 18:10:58-08]

This is difficult to answer without more details and a sample image.  ExifTool will write
all date tags in a JPEG or TIFF image, but I can imagine a few reasons why you may
be having problems:

1) Perhaps you are setting the wrong tag?  Verify using 'exiftool -s -a' which tag name you want to write,
then be sure to write them all.  (you'll see this answer if you read the FAQ)

2) Some software caches meta information.  So sometimes even if you change something properly it may
not show up.  If this is a problem you can try copying the file to a different name.

3) The filesystem itself maintains a file creation and modify date which isn't part of the meta information
of an image.  ExifTool has the ability to set this date (via a tag called FileModifyDate), but this feature is system
dependent and may not work on some platforms.

[Originally posted by steveste on 2006-01-20 17:31:17-08]

Sorry - I should have noted that I'm working with PNG files. I read in the documentation that PNG files have r/w support.

This is the tag I'm trying to set:

exiftool.pl -DateTimeOriginal+="2002:05:05" "Duck.png"

It works with a JPG file, but it doesn't work with a png file. I see this with verbose:

Shifting CanonRaw:DateTimeOriginal if tag already exists
Shifting XMP-exif:DateTimeOriginal if tag already exists
Shifting ExifIFD:DateTimeOriginal if tag already exists
Rewriting Duck.png...
  Editing tags in: APP1 ExifIFD IFD0 MakerNotes XMP
  Creating tags in:
  FileType = PNG

    0 image files updated
    1 image files unchanged

Also, this is on Windows XP (though I don't think that makes a difference based on the success with JPG and failure with PNG).

Perhaps it's that this flag doesn't exist in PNG files? In which case, can I somehow create the flag and then write it (I thought this would be automatic).

Thanks!

[Originally posted by exiftool on 2006-01-20 18:19:32-08]

The problem is that you are using the "+=" syntax in your comand-line argument:


"+=" is used to specify at time shift.  Therefore the effect of your command was to shift the date/time by 2002 hours, 5 minutes and 5 seconds.  It had no effect only because (apparently) there was no DateTimeOriginal to begin with.  But this is not what you intended to do.  Instead, I think you wanted to set the date/time, which you should do by specifying BOTH date AND time in the following format:


The necessary records will be added to the PNG to store this information.

I hope this makes some sense.

[Originally posted by steveste on 2006-01-20 20:00:40-08]

I had originally tried what you suggested and thought it didn't work because the Date Picture Taken column in Windows XP didn't change. But trying again, I see that the EXIF field is added, and that with a JPG file that column does get updated. But with a PNG it doesn't.

I then took another look at the PNG file that does have this column populated (it's a JPG file that I saved as PNG with an editor, and the Date Picture Taken column with date was retained). I saw that this PNG file also has this field:

Date/Time Of Last Modification

How can I modify that field? Would it be using FileModifyDate? The only reference I have for that is in the syntax of the docs (I can't enter the exact syntax, this forum doesn't let me):

exiftool DateTimeOriginal FileModifyDate dir

Can I do something like this:

exiftool.pl -FileModifyDate=7/1/05 Duck.png ?

Note, I don't want to change the modified date (which perhaps is File Modification Date/Time).

Thanks!

[Originally posted by exiftool on 2006-01-21 13:36:14-08]

You are getting confused between the tag descriptions and the tag names.  This FAQ number 2.  You should also read FAQ number 3, since this applies as well.  And it wouldn't be a bad idea to read FAQ number 5, since you are also having problems with formatting the date/time strings.

The FileModifyDate tag represents the timestamp used by your file system to record the last time the file was modified.  I don't think this is what you want to change.

Let me know if you have any questions after reading the FAQ.

P.S.  You might try bracing your text with so the forum doesn't mess with your formatting