Lens matching
Added by Steve Fosdick about 8 years ago
I am currently having trouble with the recognition of a Sigma 150-500mm f/5-6.3 lens on Canon. This lens gives a lens ID of 174 and I recently submitted a patch to include this lens in the list embedded in canonmn.cpp. This works for some picture and not others.
Eviv2 was changed recently to take the maximum aperture of a lens into account for some ID numbers and looking at those pictures where the lens is recognised correctly versus those where it is not what I believe is happening is that the lens reports the maximum aperture for the focal length it is currently set to whereas the code in canonmn.cpp assumes the lens will report the maximum aperture at any focal length. Thus depending on the focal length for that picture the maximum aperture value either matches or doesn't.
Any idea how to resolve this?
Replies (5)
RE: Lens matching - Added by Robin Mills almost 8 years ago
Steve
Has this been answered? I know Neils has dealt with a lot of these issues and patches. Is this resolved in 0.24, resolved on the trunk, or unresolved?
Robin
RE: Lens matching - Added by Steve Fosdick almost 8 years ago
It is not fixed in 0.24. Here is a snip of the output for a test pic:
Exif.CanonCs.LensType Short 1 174
Exif.CanonCs.Lens Short 3 150.0 - 500.0 mm
Exif.CanonCs.MaxAperture Short 1 F5.9
Exif.CanonCs.MinAperture Short 1 F27
This clearly shows the lens reporting a maximum aperture that is reduced by the focal length it is zoomed too and hence the lens is not matched. Another picture at which the lens reports its full maximum aperture gives the correct result.
Exif.CanonCs.LensType Short 1 Sigma 150-500mm f/5-6.3 APO DG OS HSM
Exif.CanonCs.Lens Short 3 150.0 - 500.0 mm
Exif.CanonCs.MaxAperture Short 1 F5
Exif.CanonCs.MinAperture Short 1 F23
I get exactly the same result as above with SVN trunk.
RE: Lens matching - Added by Steve Fosdick almost 8 years ago
I have found a bug report I raised for this: http://dev.exiv2.org/issues/926
RE: Lens matching - Added by Robin Mills almost 8 years ago
Thanks for the update, Steve. I see Niels has assigned himself to #926. So at least this forum topic has reached conclusion and the bug is logged and assigned.
Robin