On Thursday, April 28, 2022 at 8:49:58 AM UTC-7 [email protected] wrote:
>
>
> I may be wrong, it has been a while. The panotools/Hugin lens model
> does have a couple of flaws: the a & c parameters have an odd number
> power, whereas usually only even number powers are used for lens
> models (which is why we generally recommend starting with just the b
> parameter); the angle of view parameter is locked to the width of the
> image, but the lens correction parameters are scaled to the narrowest
> dimension of the image (which is the height for landscape shots and
> the width for portrait shots), the result is that you can't reuse the
> same parameters for landscape/portrait images. These have never been
> fixed because it would break existing PTO projects and they don't
> cause any problems in practice.
>
If the documentation is correct, the hugin eqn is:
Rsrc = (a * Rdest^3 + b * Rdest^2 + c * Rdest + d) * Rdest
So when you multiply the elements inside the parenthesis by outside the
parenthesis, "Rdest", the powers all increase by one, and will match the
lensfun eqn.
But as you point out, if the scaling of the maximum dimension for scaling
is not the same, then the coefs are not compatible. Thanks for sharing
your insight. I suspect TCA coefs are also incompatible for the same
reason.
Like you say, a little algebra would convert from one system to another.
> To the optimiser, the d & e parameters resemble the TrX and TrY
> parameters at the small scale, so sometimes you can get strange
> results mixing them.
>
I hadn't even considered that, but I see the problem. Probably best not to
optimize d&e if TrX and TrY are being optimized.
Thanks Bruno!
Jeff
>
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