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

[douglas wilkins]

 --- 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.

> 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


	
	
		
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