[ptx] Hugin: strange behavior of focal length <-> FOV arithmetic

[Emmanuel]

Le mardi 1 Février 2005 05:21, douglas wilkins a écrit :
>  --- jeffrey-wilson at cinci.rr.com wrote:
> > My problem might be related to a post Dec 21, 2004
> > by Stanislav Brabec with the above subject.
>
> http://www.email-lists.org/pipermail/ptx/2004-December/002942.html
>
> >  The focal length of Sony Cybershot DSC-P1 and V1
> > are technically about 7-21mm.  According to a Sony
> > webpage for a Mavica, 7mm is about equivalent to
> > 34mm in conventional 35mm film.
> >  When Hugin loads the EXIF information from these
> > images, it sets the focal length at 7 and
> > consequentially blows up the degrees of view(v) to
> > 137.5.  After running an optimize there are large
> > deviations (maximum 157).  After a lot of fiddling,
> > sometimes the v drops to 50.6 and focal length
> > adjusts to 38.1 (crop stays at 1)...reasonable
> > values.  Alternately, adjusting the crop factor to
> > 5.443 will keep the focal length at 7mm and give me
> > a appropriate view of 50.6.  I assume the crop
> > factor is missing from my EXIF data and causes the
> > problem in the first place, right?
>
> Indeed that is the problem :-(
>
> >  I imagine Hugin might have similar problems with
> > many consumer/pro-sumer digital cameras...at least
> > the Sonys.  Thankfully 0.4beta has the Lens
> > management feature to work around this issue, and I
> > have saved my Lens Project File.  Maybe there should
> > be a checkbox/feature for translating these focal
> > lengths?
>
> Once the dust has settled on the 0.5 beta, we will be
> working on this issue.

I think Ihave the same kind of problem with my olympus C40Zoom
An example of what exif comes out of my camera: 

File name    : pc160078.jpg
File size    : 821151 bytes
File date    : 2004:12:16 20:55:00
Camera make  : OLYMPUS OPTICAL CO.,LTD
Camera model : C40Z,D40Z
Date/Time    : 2004:12:16 20:55:01
Resolution   : 2272 x 1704
Flash used   : No
Focal length :  7.5mm
Exposure time: 0.0020 s  (1/500)
Aperture     : f/8.0
ISO equiv.   : 100
Metering Mode: matrix
Exposure prog: auto
Jpeg process : Baseline


> > Is this only a Sony issue?  That Minolta
> > DiMAGE A1 also sets the focal length at ~7mm, but
> > seems to have a crop factor set in the images.
>
> No, it is not just a sony issue, there are many
> cameras which do not output the "crop factor". We will
> be  correcting this problem relatively soon. :-)
>
> regards,
> Doug