Lens Metadata for full manual lenses (with no electronic contacts)?

[abgestumpft]

Hi,

I have a full manual lens with no electronic contacts (Samyang 7.5mm Fisheye) -> no EXIF data about Lens, Aperture, Focal Lenght,... written.
But my Olympus EM 1.3 has a feature to create sets of manual lenses where I can add some info which is then written to EXIF data. What I have added is:
Lens Name: Samyang 7.5mm F3.5 UMC Fish   -> this is a plain text field, I could add anything here...
Focal Lenght: 7.5mm
Aperture Value: F5.60

Both focal length and aperture value are detected by iMatch.
But the Lens is showing as "none".

When checking with EXIFtool this is what I found on lens:
Lens Type                       : None
Lens Serial Number              :
Lens Firmware Version           : 0
Max Aperture At Min Focal       : 0.0
Max Aperture At Max Focal       : 0.0
Min Focal Length                : 0
Max Focal Length                : 0
Max Aperture                    : 0.0
Lens Properties                 : 0x0
Lens Info                       : ?mm f/?
Lens Model                      : Samyang 7.5mm F3.5 UMC Fish
Lens ID                         : None

Is there a way I can make iMatch detect the Lens info?
I can filter on all affected images with: Focal Length: 7.5mm and Lens: none
But the "Lens" tag is marked as read-only.



thanks
Sebastian

[abgestumpft]

One more thing I checked, and I think I now why it shows up like this in iMatch.
I found in an older thread, that iMatch uses this order to determine the Lens from Exif Data:
Composite\LensID\LensID
Exif::Main\42036\LensModel
Exif::Main\42034\LensInfo
Composite\LensID-4\LensID
Composite\LensID-3\LensID
Composite\LensID-2\LensID
Composite\LensSpec\LensSpec

With the program: Metadata++ (a nice Exiftool GUI) it shows that:
Composite\LensID\LensID = "none"
Exif::Main\42036\LensModel = "Samyang 7.5mm F3.5 UMC Fish"

So iMatch will pick the lens name from Composite\LensID\LensID (because tag is set to "none") and write it as "none".

Is there a smart way to fix this?
E.g. in iMatch and transfer "Exif::Main\42036\LensModel" to "Lens" ?
Or via Exiftool / Metadata++ and try to delete the LensID tag an rescan files in iMatch (not sure if deleting would have any negative side effects)...

[Mario]

IMatch offers the Metadata Mechanic and Metadata Templates. They allow you to copy data between tags.

[abgestumpft]

Thanks for the quick answer!

Doing a quick test with one file in test-catalog:
With Metadata Mechanic I first tried to replace the Lens value itself -> nothing happened
photools.com::IMatch\2900\lens\0
set to
Samyang 7.5mm F3.5 UMC Fish

But when I use the LensID it is working (and iMatch automatically updates the Lens)
Composite\Exif-LensID\LensID\0
set to
Samyang 7.5mm F3.5 UMC Fish

thanks again -> will now work on fixing this globally in my catalog...

[Mario]

The problem is that there is no "lens id" or "lens name".
Different camera vendors store different things in different tags. It's all numeric.
ExifTool tries to figure out the best lens name by looking at different tags, then consulting internal tables to map the lens id (different camera vendors use the same id for different lenses) based on the make / model to the most likely human-readable lens name. It's all pretty messy - the camera vendors are to blame but don't give a shit.
XMP could solve all that.

Since you don't know which ids to update and if they do what you thing, your lens data may be reset back to "none" after write-back.
Because ExifTool does not have a reverse lookup for your custom lens name or tag. So beware. I don't analyze or test this.
Lens data is supposed to be written by the camera, not changed after the fact.

Which is also the reason why IMatch tries to many lens tags. I have not seen "none" yet for the Composite lens tag, though...
Could even be "Keine" when ExifTool is used with a German locale, or whatever other language.

[abgestumpft]

This LensID = "None" seems to be an Olympus Special.
When checking the numerical value of the LensID tag it looks like this:
======== P4131261.ORF
Lens ID                         : 0 00 00

And for Olympus Lens values:
https://exiftool.org/TagNames/Olympus.html#LensType

it is defined in exiftool:
'0 00 00'   = None

I also did a test shot when adding the lens info on the olympus was disabled with the Samyang: also LensID='0 00 00'
So this seems to be default on Olympus cameras when lens is not communicating its LensID (full manual lenses).