FOV and orientation

[Torsten Bronger]

Hallöchen!

How is the FOV lens parameter in Hugin defined? Always the
horizontal axis, always the longer axis, always the shorter axis?

Tschö,
Torsten.

--
Torsten Bronger Jabber ID: torsten...@jabber.rwth-aachen.de
or http://bronger-jmp.appspot.com

[Bruno Postle]

On 3 March 2014 10:25, Torsten Bronger <torsten...@gmail.com> wrote:

How is the FOV lens parameter in Hugin defined?  Always the
horizontal axis, always the longer axis, always the shorter axis?

Always horizontal, this is inherited from the panotools lens model.

--
Bruno

[Torsten Bronger]

Hallöchen!

Then, I'd like to define the FOV on the *shorter* axis for the
Lensfun project. Lensfun needs a clearer definition than Hugin
because it doesn't have the image size but only crop factor and
aspect ratio >= 1. By using the shorter axis, we can re-use the
scaling parameters calculated for the distortion coordinate system,
and needn't introduce yet another coordinate system.

However, Hugin must then re-calculate the FOV value returned by the
Lensfun database for the particular projection and image
orientation. For the general case, it must do so anyway because
users may feed images in any orientation into Hugin.

I'm about to implement this in Lensfun today, but it is not much
code, and I can wait with it if someone on this list wants to talk
about it.

[Torsten Bronger]

Hallöchen!

Torsten Bronger writes:

> Hallöchen!
>
> Bruno Postle writes:
>
>> On 3 March 2014 10:25, Torsten Bronger <torsten...@gmail.com> wrote:
>>
>>> How is the FOV lens parameter in Hugin defined? Always the
>>> horizontal axis, always the longer axis, always the shorter
>>> axis?
>>
>> Always horizontal, this is inherited from the panotools lens
>> model.
>
> Then, I'd like to define the FOV on the *shorter* axis for the
> Lensfun project.

For the Lensfun project, a very nice alternative would be not to
store the FOV at all but the actual focal length like this:

<actual-focal-length focal="8" actual="8.05" />

This would be completely independent of aspect ratio, orientation,
and crop factor. And, it is quite easy for Hugin to get the FOV
from it. AFAICS, no other lensfun-using project uses the FOV so
far. What do you think?

[Torsten Bronger]

Hallöchen!

Torsten Bronger writes:

> Bruno Postle writes:
>
>> On 3 March 2014 10:25, Torsten Bronger <torsten...@gmail.com> wrote:
>>
>>> How is the FOV lens parameter in Hugin defined? Always the
>>> horizontal axis, always the longer axis, always the shorter
>>> axis?
>>
>> Always horizontal, this is inherited from the panotools lens
>> model.
>
> Then, I'd like to define the FOV on the *shorter* axis for the
> Lensfun project.

I did it now this way, but for the *longer* axis. This should be
compatible with Hugin in almost all cases.

> [...]

>
> However, Hugin must then re-calculate the FOV value returned by
> the Lensfun database for the particular projection and image
> orientation.

This is still necessary, for portrait orientation.