On Tue 12-Jul-2011 at 17:43 +1000, Greg 'groggy' Lehey wrote:
On Monday, 11 July 2011 at 23:55:25 +0100, Bruno Postle wrote:
- The way Terry did it, creating the control points from the "Images"
window, is vastly superior to the way I tried it the first time from
the "Assistant" window.
Yes, the assistant is a wizard for 'normal' panoramas that have lots
of partial overlap between photos. As soon as you want to do
something different you need to take control yourself.
If your photos have different focal lengths, then you can 'unlink'
the 'degrees of view (v)' lens parameter before optimisation.
This is the "link" box in the And this, I think, is part of the
question, though I didn't see any difference between linking and not
linking.
If angle of view is 'linked' then the optimiser will find a solution
where all photos have the same angle of view, if it is 'unlinked'
then it will also search solutions where each photo has a different
angle of view.
But it seems that Hugin is relying on the focal length information
from EXIF, and in the case of my camera, that information is very
inaccurate.
The EXIF is just used for the initial values when you start the
project. If you run the optimiser and optimise angle of view, then
Hugin will find new values that fit the data better.
For the fun of it, I tried changing the focal length spec for the
second and third images. I left the first one at 23 mm, but by
changing the focal length of the other two. At 22.421 mm, the errors
dropped to an average of 0.3 pixel, with a maximum of 0.92 pixel.
Yes, for a set of photos with a narrow total angle of view like
this, it doesn't much matter if the actual angle of view is
inaccurate - So long as the relative values are good.
In practice, with a 'narrow' project like this you don't have enough
data to discover the precise angle of view anyway.
There's more information, including images and discussion, at
http://www.lemis.com/grog/diary.php#D11-3 , though that doesn't
include the change of focal length. I'm continuing to experiment.
--
Bruno
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