On Sat, Mar 30, 2013 at 9:52 PM, Leonard Evens
<[email protected]>wrote:
> On Sat, 2013-03-09 at 12:30 +0100, Pascal de Bruijn wrote:
> > On Sat, Mar 9, 2013 at 12:56 AM, Leonard Evens
> > <[email protected]> wrote:
> > > I recently got a Nikon D800, and I am having problems with lens
> > > correction.
> > >
> > > I've used it with two lenses.
> > >
> > > It recognizes the 24-70 mm lens from the exif information, but it
> > > doesn't allow me to then select that lens, which, I've found, is
> > > necessary for lens correction to work.
> >
> > The lens isn't automatically selected? Possibly this happens because
> > of a naming mismatch between Exiv2 and Lensfun? Are you sure the 24-70
> > available in Lensfun is actually the lens you have? Some lenses have
> > incompatible variations...
>
> I'm not sure what you mean here.
>
For many manufacturers there are lenses that are named in nearly identical
ways, but they are not truly the same lens...
So the lensfun database might have a Nikkor 50 f1.4 USM, and you may have a
Nikkor 50mm f1.4, which are two different lenses even though some users may
"think" it's the same thing.
I'm not sure if this is the case for you... I was just asking to
doublecheck if the lens name in the lensfun database is absolutely
identical to that reported by darktable (i.e. exiv2).
I guess you can ignore this now :)
Let me explain again. Darktable will find the lens from the Exif
> information. But even when it does, it won't correct the distortion. I
> have to click on the lens in the darktable lens correction module. A
> menu comes up showing manufacturers. If I select the correct
> manufacturer, it gives me a list of possible lenses. If I then select
> the right lens, it proceeds to do the lens correction. This works for
> example with my Nikon D90, a Nikkor 18-200 mm lens and a Sigma 10-10 mm
> lens. If I don't go through the rather complicated procedure, the
> distortion correction is not done. It seems that although darktable
> has read the correct lens from the exif information, it doesn't actually
> know which lens it is until I do the extra work.
>
> For my new Nikon D800 and the Nikkor 24-70 mm lens, the lens information
> is correctly shown in the exif data shown in darktable.
> (Also
> exiv2 -pt image_name
> shows the lens description.)
> But when I click on it in the lens correction module, nothing happens.
> I am not given a list of manufacturers and an opportunity to select the
> right lens. This may be explained because although the camera model
> shows Nikon D800, read from the exif info, as shown by darktable, if I
> click on that, getting a list of manufacturers, if I choose Nikon. I get
> a list of models NOT including the D800. So although the exif info has
> told darktable the correct camera and lens, in reality, it recognizes
> neither.
>
> I presume the problem may be that the Lensfun database being used by my
> version of darktable doesn't know about the Nikon D800 or about the
> Nikor 24-70 mm lens.
>
I have a up to date copy of Lensfun here, and the Nikkor 24-70 isn't
listed... So nobody who owns that lens calculated and submitted correction
data yet.
This article has some links, on how to calculate correction parameters:
http://www.darktable.org/2012/10/whats-involved-with-adding-support-for-new-cameras/
I have used Hugin in the past, and I suppose that if I work at it for
> several days I can figure out how to add the right information to
> Lensfun. But I am 79 years old, I am not going to live forever. I was
> hoping that someone else would deal with the issue.
I just checked the sample you provided... But it seems there just isn't a
correction model available for the Nikkor 24-70 in the lensfun database...
> After all,
> darktable claims to support the Nikon D800, but apparently that is not
> really the case.
Lens correction is hardly critical.
More importantly we use an external libraries for reading the EXIF metadata
and translating Nikon's cryptic codes into proper lens names and applying
lens corrections and it's impossible for anybody to test all of this, since
we simply don't have access to all camera's and all lenses. Neither do
these external projects (Exiv2/Lensfun).
If your "idea" of support, is everything Nikon does, then you are
completely limited to Nikon's own software. FULL STOP.
> The D800 has been around for several years and the
> 24-70 mm lens is a standard lens for it.
>
I'm not sure how this is relevant in any way.
Lens corrections are generated by users, collated by the Lensfun developers.
Apparently nobody who owns the lens and uses open source software cared
enough to do the work to generate a correction model.
> > > But it doesn't recognize the 70-200 mm, f/4, lens from the exif file
> > > although that information is in that file, giving the number 178
> > > instead. So, in that case, lens correction also doesn't work.
> >
> > That means Exiv2 doesn't have the numeric lens ID in it's database yet.
> >
> > Or you using at least Exiv2 0.23?
> >
> > Or if you're using Ubuntu, are you using my Ubuntu-Release-Plus-PPA?
> > Which has a patched version of Exiv2 (0.23)? If so, please do report a
> > feature request to the Exiv2 project.
>
Regards,
Pascal de Bruijn
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