I've been successfully changing dates on my slide scans using “Metadata–>Adjust date & time,” including the “Also change master file.”
Now, I'm seeing the following error when attempting to change the date on any of my photos:
“Unable to adjust master file”
“Aperture was not able to adjust the date and time of the master file 'IMG_0008.jpg' because it has a format that does not permit date modification.”
Any idea what's needed to resolve this?