Re: Panorama Tools

[Helmut Dersch <der@xxxxxxxxxxxxxxxx>]

Glenn Barry wrote:
> 
> Hi All,
> 
> I am having problems determining correction co-efficients (Panorama
> tools correct) and Field of view values (Panorama Tools Remap) for a
> 15mm F2.8 AF Sigma fisheye. When I run multiple optimizations my values
> seem to fluctuate and the between actual and desired values between
> correction points don't decrease.
> Has anybody else had any success determining these values that they
> could share?
> 

Hi Glenn,

I am using this lens on 35mm format and have an example on-line:
<http://www.fh-furtwangen.de/~dersch/example.zip>
It includes an optimizer script with correction values.
However, this can not be directly applied to 120 film images
since the width of the image (field-of-view) matters.

Correction values usually scatter somewhat for different sets
of images and/or feature points since not only the radial lens
distortions but also other geometric errors (nodal point alignment,
scanner errors, non-radial distortions etc) contribute.

For your set-up, you need to crop the images to the circle,
and then use one set with ample overlap (eg 3-4 for a 360 degree pano)
with lots of feature points. Try to be as accurate as possible
with the alignment and the estimates for yaw/pitch/roll. Then
optimize position (yaw/pitch/roll), radial coefficients (a,b,c)
and field of view (v). You probably don't need to optimize
the position of the optical center (d,e) as in the example
on my site, since it should be close to the center of the circle.


> One thing to bear in mind is that I am shooting full circle fisheye with
> this lens on 120.
> 

Could you share some details on this setup. How large is the 
image circle, what is the angular coverage?

Regards

Helmut Dersch