LNC Order vs Iterat...
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LNC Order vs Iterations tradeoff  


Molecular Cloud Customer
Joined: 1 year ago
Posts: 5
August 1, 2020 00:56  

What is the tradeoff between using a higher order of LNC with a low number of iterations vs a lower order LNC with higher iterations?  When would you choose more iterations or a higher order?

Thanks anyone for input!


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Main Sequence Star Customer
Joined: 3 years ago
Posts: 27
August 19, 2020 19:50  

The two parameters speak to two different aspects of LNC:

Degree determine the "shape" of the correction: 1st degree means it can only correct a linear gradient (bright at one end, dark at the other), whereas 2nd or higher degree can fit a curve on the gradient. (a "standard" vignette can probably be estimated well by a 2nd degree). Changing the degree has (basically) no impact on the performance/speed, as it's only determining "how do I correct the gradient I'm detecting".

The iteration # determines how many time you run the computation, by fitting a first correction (iteration 1), then looking at whether that can be improved (iteration 2) and on and on. That has a direct impact on the performance.

--> The degree will determine the complexity of the correction you can compute, the iterations how well that correction is fitted.