Author Topic: LensType Garble  (Read 636 times)

Offline Mark S

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LensType Garble
« on: December 03, 2019, 04:54:17 PM »
On Windows 10 (v1903) with PM6 (build 3954) I am getting some garbled text in an EXIF field, specifically the Canon LensType field. Checking the files in EXIFtool shows no garbled text in the field, nor does the garbled text show up in PM4.6.9

So far I have only seen this behavior with Canon EF-M cameras and PM6 (Nikon DSLR, Canon DSLR, Sony A7RII all seem OK). It became very noticeable once I started beta testing PMPlus6 (build 4073), but as mentioned, it exists in PM6 (3954) also.

PNG image files attached.

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Offline Kirk Baker

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Re: LensType Garble
« Reply #1 on: December 03, 2019, 05:08:11 PM »
Mark,

Can you share one of your CR2 files that exhibits this behavior?

Thanks,

-Kirk

Offline Mark S

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Re: LensType Garble
« Reply #2 on: December 03, 2019, 05:34:06 PM »
Kirk,

Yes I can share a file, but how?

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Offline Kirk Baker

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Re: LensType Garble
« Reply #3 on: December 03, 2019, 05:38:16 PM »
Mark,

Yes I can share a file, but how?

If you have a service like DropBox, you could upload the file there and then share a link with me, or I can provide you with FTP server credentials (to our server) and you can FTP upload the file there.

Thanks,

-Kirk

Offline Kirk Baker

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Re: LensType Garble
« Reply #4 on: December 03, 2019, 09:09:42 PM »
Mark,

Thanks for the sample file.  We're able to reproduce the problem and we're looking into it.

-Kirk

Offline dennis

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Re: LensType Garble
« Reply #5 on: December 10, 2019, 11:52:31 AM »
Mark,

I looked into this problem and have a fix.  It looks like the camera is not putting the correct lens parameters (for "Sigma 8-16mm f/4.5-5.6 DC HSM") unless the focal length is 8.  The camera writes "-mm" into the Exif lens model and PM had a bug with the short string (it was using this as an offset as if the string were longer).

I'm thinking that perhaps the camera is somehow changing how the lens parameters are written when focal length is changed.  These lens parameters are supposed to remain fixed regardless of the focal length or aperture (since they describe the lens) and this is affecting how we look up the lens type string.  We don't find a match and therefore try to use the Exif lens field instead (which apparently will be just "-mm" in some or all cases).

Can you post a set of JPEG files (don't need CR2) with this lens taken at 8mm, 10mm, 12mm, and 16mm (IOW I need min/max focal length and a few in-between).  We might be able to fudge our lens parameter lookup to accommodate these parameters changing.

--dennis

Offline Mark S

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Re: LensType Garble
« Reply #6 on: December 10, 2019, 12:47:37 PM »
Thanks Dennis.

I will be able to send some jpg images later this evening.

I have added many more images to the catalog of the beta version of PM6+ and have only seen this behavior with just this lens and the Canon EF-M cameras (M6 and M100). It is a third party lens attached to the camera via a Canon EF-to-EFm adapter, so I wasn't expecting much wrt lens information.

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Offline dennis

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Re: LensType Garble
« Reply #7 on: December 11, 2019, 10:41:29 AM »
Mark,

Thanks for the files.  This confirms my suspicion that Canon is flagging the maker note lens parameter for max aperture based upon the focal length rather than keeping this constant as one would expect for a lens description.  We had only the case with focal length of 8mm in our lens description list, and this would produce the full lens description "Sigma 8-16mm f/4.5-5.6 DC HSM". But regardless, Canon is always writing "-mm" into the standard Exif lens model field.

We will add in the cases for focal lengths > 8mm and <= 16mm for the same lens description.

I suspect this problem will also exist with other Sigma lenses such as the following, but we don't have any image samples to verify.
  Sigma 12-24mm f/4.5-5.6 DG HSM II
  Sigma 17-70mm f/2.8-4 DC Macro OS HSM
  Sigma 18-50mm f/2.8-4.5 DC OS HSM
  Sigma 18-125mm f/3.8-5.6 DC OS HSM
  Sigma 18-200mm f/3.5-6.3 DC OS HSM [II]
  Sigma 18-250mm f/3.5-6.3 DC OS HSM
  Sigma 50-200mm f/4-5.6 DC OS HSM
  Sigma 70-300mm f/4-5.6 DG OS

Offline Mark S

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Re: LensType Garble
« Reply #8 on: December 11, 2019, 12:53:01 PM »
Dennis,

That is interesting. I find it curious that when the lens is used on a Canon 70D the {lenstype} returns "8-16mm" at all focal lengths rather than the "Sigma 8-16 f/4.5-5.6 DC HSM" that the M6 returns when at 8mm (or other focal lengths when the PM6 list is corrected).

I know it is not on your list of suspects, but I have some older images from a "Sigma 18-200mm f/3.8-5.6 DC OS" (not HSM) which reports correctly in the {lenstype} at various focal lengths. (editorial: not a great lens at all)

Thanks for resolving this Dennis, much appreciated.
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Offline dennis

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Re: LensType Garble
« Reply #9 on: December 11, 2019, 05:41:20 PM »
If it ain't broke then don't fix it ;)

I suspect this may be an "artifact" of using the Canon EF-to-EFm adapter.

If {lenstype} is returning something basic like "8-16mm" it might be the best the 70D camera comes up with.  Better than "-mm" at least!

Maybe you can send me just a few JPEGs with that lens connected to 70D (8mm and 16mm plus another in-between)?

--dennis

Offline Mark S

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Re: LensType Garble
« Reply #10 on: December 11, 2019, 08:14:01 PM »
Hi Dennis,

I have added 70D and 90D jpegs (same lens) into the same folder as before. The 90D {lentype} is not what I expected.
 
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Offline dennis

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Re: LensType Garble
« Reply #11 on: December 12, 2019, 11:45:47 AM »
Mark,

Well different models write different stuff, both for Exif lens model and for the value I use to lookup lens description.

This will all be fixed in the next build, at least for all the sample images you have sent me (M6, M100, 70D, and 90D).  There was one last tweak for focal length = 16 that we had to make for 70D and 90D.

--dennis
« Last Edit: December 12, 2019, 11:48:37 AM by Kirk Baker »

Offline Mark S

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Re: LensType Garble
« Reply #12 on: December 12, 2019, 12:04:58 PM »
Thanks again, Dennis.

Great product with impressive support!

Cheers,
-- Mark --