Automatic lens correction gives poor results

[Mudman]

I’m new to AP and still learning.  However, I’ve noticed automatic lens correction of Raw files using the embedded lens profiles does not give very good results, particularly for wider angle lenses.  Specifically, the corrected images are not the correct scale (either cropped or expanded) compared to JPG images produced by the camera.  Distortion is mainly corrected accurately, but for some lenses I’ve tested, there is noticeable barrel distortion in the corrected image.

I’ve previously used Adobe Camera Raw, which consistently and accurately corrects scale, distortion, vignetting etc from the embedded lens profiles.  My question therefore, are the embedded lens profiles used by AP2 (from lensfun?) the same as used by ACR, and if so, why are they giving different results?

Attached are example images from the Olympus M.Zuiko 9-18mm on an OM Systems OM-5: 1. Camera corrected JPG; 2. Auto corrected with AP2; 3. Auto corrected with ACR.

[David in Яuislip]

Possibly a ropey profile from Lensfun
I don't have that lens but here's an example using an Olympus 8-25 @ 8mm. Green on the outside shows very good correction, original moved southeast a bit is pretty wonky
Note that Photo can't read embedded lens profiles like ACR so uses Lensfun
Can you post the raw file?

[Mudman]

Thanks for your comment.  I hadn't realised Lensfun uses different profiles to ACR, so I think that explains it.  For my example image, AP2 didn't actually choose a profile automatically, so I needed to pick from the dropdown list - 'Olympus Zuiko Digital ED 9-18mm f/4.0-5.6'.  But on comparing the JPG processed by AP2, there doesn't seem to be any correction applied at all (visually the same as the Raw file).  I've added a link to download the Raw file, as it's too big to add directly.

https://1drv.ms/i/c/89ba5929200936f4/ETyqXRL11fxFnuldIFQgjWQB_Iv_SdUnKR_TmekKcPEy4A?e=v0t4xP

[David in Яuislip]

Interesting one this

Exiftool on your file reports
Lens Model : OM 9-18mm F4.0-5.6 II
Unfortunately the Lensfun data is for the old Olympus M.Zuiko Digital ED 9-18mm F/4.0-5.6 so you're goosed until Lensfun is updated, see
https://github.com/lensfun/lensfun/blob/master/data/db/om-system.xml

The interesting bit is that there are two entries for this lens in PhotoV1 that give different corrections, I think this is a world first, maybe V2 is better. They are in the zip file so this forum doesn't mangle them

Adobe DNG Converter provides millions of .lcp files which can be placed in Photo's Lens Profile folder when Lensfun .xml's aren't available. But μ4/3 correction is done by ACR using the embedded lens profiles so there are no .lcp's for these lenses

I have used your uncorrected image in Hugin Lens calibration GUI to generate new values for a, b and c at 9mm and they are in the attached xml. You can extend this if you wish for the other focal lengths. Otherwise try OM Workspace from the OM System website, this ought to provide the best correction, or do what I do and use DxO PhotoLab

Olympus9-18mmF4-56.xml TwoVersions.zip

[Mudman]

That's brillant, I'll experiment with this.  Many thanks for your help.

[kananbrooks]

It’s frustrating when the results don’t match expectations especialy with specific lenses.
Sometimes manual tweaks make a big difference in achieving the right look.