# ExifTool FAQ

#### "Is there a forum for discussing ExifTool issues?"

> An ExifTool forum is provided by CPAN at http://www.cpanforum.com/dist/Image-ExifTool

#### "ExifTool reports the wrong value for a tag",
"ExifTool doesn't write a tag properly", or
"Other software can't read information written by ExifTool"

> Make sure you are looking at the right information. Many tags are duplicated in different locations within an image. When in doubt, use `'exiftool -a -G1 FILENAME'` to show all tags and their locations in the file. In this command, `'-a'` allows duplicate tags to be displayed, `'-G1'` shows the family 1 group name (ie. the location) of each tag, and `'FILENAME'` is the name of your image file.

> You can read or write information in a specific location if necessary by prefixing the tag name on the command line with the desired group name. ie) `'-ExifIFD:DateTimeOriginal'`

#### "ExifTool reports more than one shutter speed or aperture value, and they are slightly different"

> There are a number of different ways that aperture and shutter speed information get saved in an image. The standard EXIF values (EXIF:FNumber and EXIF:ExposureTime) should correspond to the values displayed by your camera, but these values may have been rounded off. The APEX values (EXIF:ApertureValue and EXIF:ShutterSpeedValue) may be different due to their own round-off errors. If available, the MakerNotes values are the typically the most accurate because they haven't been rounded off at all, but you may see odd values like 1/102 instead of 1/100, etc.

#### "I can't delete all EXIF information from a TIFF file using `'exiftool -exif:all= img.tif'`"

> This is because of the way a TIFF file is structured. With a JPEG image, this command will remove IFD0 (the main Image File Directory) as well as any subdirectories, thus removing all EXIF information. But with the TIFF format, the main image itself is stored in IFD0, so deleting this directory would destroy the image. Instead, ExifTool just deletes the ExifIFD subdirectory, so any information stored in other directories is preserved.

> Use `'exiftool -a -G1 img.tif'` to see where the information is stored. Any information remaining in other IFD's must be deleted separately from a TIFF file if desired.

Last revised May 24, 2005

<-- Back to ExifTool home page