On Wed, 2013-03-06 at 17:47 +1100, Russell Edwards wrote: > Hi, > > I was just fiddling with lens correction on an image taken with my > Pentax K5II and a Samyang 14mm/2.8 lens. > > In the lens correction module it comes up with "Pentax K-5 II" for the > camera, and "A Series Lens" for the lens, and applies no noticeable > distortion corrections.
My experience is that, despite listing the lens correctly from the exif data, darktable doesn't actually know what the lens is for the purpose of correcting distortion. I have to explicitly reenter it, Then it does the lens correction. I should also add that although it does a good job if the correction is small or moderate, it doesn't fully correct barrel distortion if the required correction is large. In such cases I can do much better in gimp using the gimplensfun filter. > > If I change the camera to another Pentax APS-C camera (or a Generic > 1.5x camera), suddenly it applies a pretty good pincushion correction. > > How can this be, when darktable has apparently not identified my lens? > > This lens does not communicate electronically with the camera. I told > the camera the focal length was 15mm (as it has no 14mm option) and this > is reflected in the exif data. Has darktable somehow just made a > reasonable guess at how much pincushion a 15mm lens on APS-C will have > ?? > > I will make the effort to calibrate the lens and submit it to LensFun > but I am just curious what's going on here and where darktable is > getting its correction parameters from in this instance. I am using > darktable 1.1+1175~g2434bf0. > > Secondly it won't let me choose any other lens unless I select a camera > other than the automatic "Pentax K-5 II". > > Thanks in advance > > Russell > > > ------------------------------------------------------------------------------ > Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester > Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the > endpoint security space. For insight on selecting the right partner to > tackle endpoint security challenges, access the full report. > http://p.sf.net/sfu/symantec-dev2dev > _______________________________________________ > Darktable-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/darktable-users -- Leonard Evens [email protected] Professor Emeritus, Department of Mathematics, Northwestern University ------------------------------------------------------------------------------ Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the endpoint security space. For insight on selecting the right partner to tackle endpoint security challenges, access the full report. http://p.sf.net/sfu/symantec-dev2dev _______________________________________________ Darktable-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/darktable-users
