Why is Darktable lens correction greyed out for a Tamron 18-270mm on Ubuntu?
Asked 10/5/2016
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2 answers
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I'm using Darktable 2.0.6 on Ubuntu 16.04 with a Tamron 18-270mm F/3.5-6.3 Di II VC PZD. In the lens correction module, Darktable shows the correct lens name, but the correction options are greyed out. The lens is listed in the Lensfun XML files under /usr/share/lensfun, and I've already updated the Lensfun library. What causes this, and how can I make lens correction work?
Originally by user57234. Source · Licensed CC BY-SA 4.0
user57234
9y ago
2 Answers
2
Lensfun does not offer calibrations for a particular lens model that were done with a too small sensor. In your case, the calibration was made with a Canon, and you use a Nikon. Canon's APS-C is smaller than Nikon's. Because this difference is small and there are so many third-party lenses, Lensfun is less picky in newer versions about that.
Solutions: Update your Lensfun, or set the crop factor in the XML file manually to 1.5 for both the lens and your camera.
Originally by user18998. Source · Licensed CC BY-SA 4.0
user18998
9y ago
0
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This usually happens because Lensfun has a lens entry but no usable calibration for your camera/sensor crop.
For this Tamron, the available calibration was made on a Canon APS-C body, while you’re using Nikon APS-C. Older Lensfun/Darktable combinations can reject that calibration because Canon APS-C is slightly smaller than Nikon APS-C, so the correction controls stay disabled.
What to do:
- Update Lensfun to a newer version. Newer Lensfun releases are less strict about these small APS-C crop differences, especially for third-party lenses.
- If needed, manually edit the Lensfun XML so the crop factor matches your camera, e.g. set the crop factor to 1.5 for both the lens and your camera entry.
So the issue is not that Darktable can’t identify the lens—it’s that the calibration data isn’t considered compatible with your camera by the older Lensfun version.
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