Aperture reports the wrong lens on my EOS M

I'd suggest using Aperture's "Send Feedback" option.

Just in case you want to fix the wrong display of the lens, you might want to use exiftool to write the correct lens tag as a temporary work-around, see this user tip:

Modifying EXIF tags of Originals Using exiftool: camera, lens, gps

More likely an OS issue than an Aperture issue. If you do a "Get Info" on the file in the Finder (command-I) does it have any lens info?

Thanks for the tip, but I think it's a Aperture issue, not an issue with the EXIF data. if I open the file with Canon's DPP, everything is reported correctly...

It definitely is an Aperture issue, but it has been going on for quite some time now, and I doubt that it will will be fixed soon. That is why I have rewitten the exif on certain lenses to be able to see the correct lens tag in Aperture.

You need to install the free exiftool to be able to do that; then use a Terminal command.

Have you seen the user tip I pointed to?

Modifying EXIF tags of Originals Using exiftool: camera, lens, gps

I tried exiftool, but it didn't change anyting in Aperture.

for me this worked - for example to tag my old Nikon F2 slides:

exiftool -overwrite_original_in_place -preserve "-Lens=Nikkor 1:3,5 f=55 mm" /mydirectorypath

touch /mydirectorypath/*.*

where /mydirectorypath is pointing to the directory containing the original image files to be changed. But the final touch command is essential: It will tell Aperture that the image has been changed, and only then will the changed tags be visible in Aperture's Info panel.

The bug is still extisting :-(

Over a year later and the problem still exists!

Bug still exists - despite a number of Aperture upgrades 😟

I am now also getting the same thing - correct focal length, aperture, but incorrect lens with my canon 30d and sigma 70 to 200 EX DG wrongly reported in Aperture as 50mm to 150mm.