EXIF Editing - Focal length 35mm equivalent

[Michael Coffey]

Firstly seasonal greetings, and here’s hoping for a better 2021.

I have a Fujifilm X100F whose focal length of lens is reported correctly but 35mm equivalent is not. Please see screenshot below.

I have read mklass’ post EXIF editing from April 1 2020 and Dub’s contribution makes me think that a Code Replacement file might rectify the issue.

I have read mklass’ post "Ability to edit lens type" and Kirk’s response makes me think PM is unlikely to change EXIF data besides modifying GPS coordinates or capture time.

The X100F camera has an APS-C sized sensor so I do not see where the issue lies in PM reading the files. Can someone please set me right on this?

Michael

[dennis]

Michael,

It's hard to say what the issue is without having an actual file to examine, but it may be that you mounted a lens that the camera doesn't "understand" fully, like whether the lens was made for APS-C or not.  If the lens is designed for full-frame (looks like a zoom with 23mm in the range), then the camera may just call it as the 35mm equivalent being the same as what the camera reports.  Normally a camera will write two Exif tags, one with focal length and another with the 35mm equivalent (which might be different or not).  But the camera could only write one tag.  I would need a sample file along with a description of the lens that was mounted (make and model).

HTH...

--dennis

[Michael Coffey]

Hello Dennis, the camera is a Fujifilm X-100F, an APSC camera with a built-in 23mm lens. I can see that PhotoMechanic is not recognising this.

If PM6 could give the correct 35mm equivalent FOV value that would be best. I do not mind changing this data manually if it is even possible in PM6.

I attach three files below - raf, xmp and jpeg files.

Thanks, and have a different, and I hope better year in 2021 than the last.

[platti]

Hi,

For some reason your X100F doesn't give the correct informations for the 35mm equivalent into the exifdata. It says in the composite flags "35 mm equivalent: 22.6 mm". This is a wrong information.
My X100V writes: "35 mm equivalent: 35.3 mm", which is the right information.

[Michael Coffey]

Thank you for your response Platti, this is basic but useful information for me. I consider this sufficient information for my initial query. Best wishes, Michael

[dennis]

Michael,

The sample JPG photo you have (which was created by Capture One 11 not directly from the camera) shows Exif focal length as 23mm (Exif tag 0x920a).  There is a different tag 0xa405 that some APS-C format cameras write which is the 35mm equivalent of the focal length, which would be 35mm.  This JPEG does NOT have this tag.  All other Exif data shows 23mm, even the lens info specs (tag 0xa432) and lens model (tag 0xa434) shows "23 mm f/2".  At bottom of Exiftool report it says focal length is "23.0 mm (35 mm equivalent: 22.6 mm)".

The RAW RAF file also does not have the 35mm equivalent tag 0xa405, but for some reason Exiftool does show at the bottom of its report "23.0 mm (35 mm equivalent: 35.4 mm)".  It also is able to correctly calculate a "Scale Factor To 35 mm Equivalent" as 1.5.  This is probably what it is doing in the absence of the 0xa405 tag.  This has some tricky math involving sensor size etc which we don't implement.

So there is nothing we can do with the JPEG saved by Capture One, and to support this for RAF we would have to implement the scale factor code.  It may be that with the JPG files created directly by the camera, Exiftool can properly calculate this scale factor as it does with the RAF.

Best would be if the camera would just write the 0xa905 tag and be done with it.

--dennis