Batch-create the Exif timestamp from the modification date

[SlavePunisher]

Hi there,

I am a newbie with ExifTool. I'm sorting my archive of family pictures, and I realize that a lot of them don't have any EXIF Timestamp. Fortunately, a lot of them have correct creation+modification dates, or a wrong creation date but a correct modification date.

I began to fix them with a third-party software, who is not able to create an Exif Timestamp, but at last I can copy Modification date to Creation date.

Then I use ExifTool to batch-copy the Modification date to the Exif Timestamp, with this command line in the Terminal:
exiftool '-DateTimeOriginal<FileModifyDate'
It works – an Exif timestamp is created from the modification date – but once fixed, the creation+modification dates are changed to the actual date... So I have to turn back to the third-party software to finally copy the Exif timestamp to Creation/Modification dates...

I think I am not doing things as they should be...  Is there a way to keep the original Modification date ?

Thanks a lot for your help !

[Phil Harvey]

Please let me know if you have any questions after reading FAQ 24.

- Phil