Floating point XMP tag value is rounded to integer

[Tom OReilly]

My configuration file contains this entry:

             CameraTriggerTime => {
                                Writable => 'rational',
                                Description => 'camera trigger time',
                                Groups => { 2 => 'Location' } },

Then I write CameraTriggerTime to an image and then display the value:

$ exiftool -config exiftool.config  -xmp-xmp:CameraTriggerTime=1584034455.86999 DSC00020.JPG 
    1 image files updated
$ exiftool -S DSC00020.JPG | grep Trigger
CameraTriggerTime: 1584034456

Why does the value of CameraTriggerTime get rounded?
Thanks!

[Phil Harvey]

A rational is a ratio of two integers, each of which have a maximum value.  Typically you only get 8 digits of precision from a 64-bit rational the way that ExifTool writes them.

- Phil

[Tom OReilly]

Thanks Phil.
So 'real' (not 'rational') displays a floating point number.

[Phil Harvey]

They both display a floating point number.  However, 'rational' is stored as a fraction, and 'real' is stored as a floating point number.

- Phil