Wrongly identified Canon 2x extender as 1.4x extender with Tamron lens

[sjjh]

exiftool 10.80 (couldn't find a fix for the bug in the change log, thus assume that it still exists) on Ubuntu 18.04.
Example file: www.muenster.de/~simonh/EQ2A0002.CR2
Used lens combination: "TAMRON SP 70-200mm F/2.8 Di VC USD G2 A025" and Canon Extender EF 2x III (normally recognized as "+2x III")
exiftool seems to only recognize the extender as an 1.4x extender:
user@host:~$ exiftool EQ2A0002.CR2 | grep "Lens ID"
Lens ID                         : Tamron SP 70-200mm F/2.8 Di VC USD G2 (A025) + 1.4x
Thus also the focal lens values are wrong.
(In case it is relevant: same problem exists with exiv2.)

Note: using the extender together with a Canon lens, it is correctly identified as 2x extender -- still the version information "III" is missing. Not sure if it should be present. See example file: www.muenster.de/~simonh/EQ2A9988.CR2

Thanks for your work!
Simon

[sjjh]

Small addition: exiv2 has a similar issue, see: http://dev.exiv2.org/issues/1361
(didn't find any possibility to edit my former post)
Simon

[sjjh]

Edit: The ambiguity with "Lens Type" seems to be more severe than I assumed, the Tamron lens is also without the extender identified as either a Canon 300mm or a Tamron lens. Thus if possible this should be corrected anyway (independently from the usage of the extender). I've uploaded another example image of the Tamron lens without an extender: https://www.dropbox.com/s/6q1d54uyraot82r/EQ2A9987.CR2?dl=0
Feel free to use all images for improving exiftool and other FOSS.

user@host:~$ exiftool EQ2A9987.CR2 | grep "Lens Type"
Lens Type                       : Canon EF 300mm f/2.8L IS II USM or Tamron Lens

Simon

[Phil Harvey]

Thanks Simon,

I'll look into this tomorrow and post back here if I have any questions.

- Phil

[Phil Harvey]

Sorry for the delay in responding.

I get this for the samples you posted with ExifTool 10.80:

Code Select Expand

> Image-ExifTool-10.80/exiftool ~/Desktop/ -ext cr2 -lenstype -lensid
======== /Users/phil/Desktop/Tamron70-200.cr2
Lens Type                       : Canon EF 300mm f/2.8L IS II USM or Tamron Lens
Lens ID                         : Tamron SP 70-200mm F/2.8 Di VC USD G2 (A025)
======== /Users/phil/Desktop/Tamron70-200with2x.cr2
Lens Type                       : Canon EF 70-200mm f/2.8L IS II USM + 2x
Lens ID                         : Canon EF 70-200mm f/2.8L IS II USM + 2x
    1 directories scanned
    2 image files read

I think this is the best I can do.  There is no way to distinguish the Tamron from the Canon lens when the extender is attached.

- Phil

[sjjh]

Thanks for your reply Phil!
Too bad that there's no way to distinguish them having the extender attached. Strange that the recognition without the extender shows a different lens (Tamron or Canon 300mm) than with the extender (Canon 200mm)
Could the recognition without the extender be improved (lens type vs. lens id), or isn't that possible either?

Simon

[Phil Harvey]

Hi Simon,

Without the extender, the lens codes for all these lenses are the same:

Canon EF 300mm f/2.8L IS II USM or Tamron Lens
Tamron SP 70-200mm f/2.8 Di VC USD G2 (A025)
Tamron 18-400mm f/3.5-6.3 Di II VC HLD (B028)
Tamron 100-400mm f/4.5-6.3 Di VC USD (A035)
Tamron 70-210mm f/4 Di VC USD (A034)
Tamron 70-210mm f/4 Di VC USD (A034) + 1.4x
Tamron SP 24-70mm f/2.8 Di VC USD G2 (A032)

Unfortunately, exact identification is difficult because of the overlapping focal-length/aperture ranges, but you should be looking at the Composite:LensID tag, not the Canon:LensType tag since the Canon 300mm is ruled out by the focal length (all these 3rd-party lenses "borrow" the LensType number of this Canon lens).

- Phil

[sjjh]

Thanks for the info and your effort. Then it seems as we'll have to stick with what we have.
Simon