Hello,

For stitching panoramic images with Hugin, recommendations for placing the 
Control Points include:
1) place Control Points for all overlapping image pairs
2) spread Control Points over the overlap image area

>From practical experience, results do improve, hence I suggest to change 
the recommendations as follows:
1a) place Control Points only for image pairs that are blended
2a) place Control Points only in the vicinity of the seam line
2b) if you move the seam line, also adapt your set of Control Points
2c) avoid placing Control Points into image corners

This request is based on stitching panoramics using images from more than a 
dozen cameras by more than half a dozen manufacturers, the number of 
panoramics being well into the triple figures.

The root reason is that with reference to the mathematically sound and 
physically motivated Brown-Conrady lens model only one distortion parameter 
is being used in hugin and panotools. Short of changing program code to 
include further (radial and possibly also non-radial) Brown-Conrady 
distortion parameters, the above recommendations mitigate the visual impact.

One might consider to change Hugin's CPFind behaviour of selecting CP 
placement areas. CPFind and Fine-tune in itself are ok.

I know I need to be careful not to be mislead by parallax effects and 
chromatic aberration. Based on mostly landscape panoramics my findings stem 
from
a) systematic inspection of the vis.*.tif files using --visualize in the 
enblend settings
b) detailed studies in several cases, observing image content shifts of 
several pixels, double figures even in corners
c) compass angle errors at the percent level when comparing hugin 
panoramics with synthetic panoramics from the udeuschle.de tool

Best regards
Klaus

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