9.16.3 Can you answer these questions?

9.16.3.1 How to fix Vignetting?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=284383

Such as this photo: 
 
I want to remove the dark corner to get this result: 
 
I know this is easy to remove in Photoshop, but I'm a MMA user so I want to know how to process it with MMA... 
[image-processing]
 

asked by yode https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=21532 Score of 1

9.16.3.2 Complex eigenvalue of a symmetric matrix

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=284582

I am working on a eigenvalue problem. I am using Eigensystem 
However, I am facing issues when I change the input parameters: 
I get complex eigenvalues. I couldn't understand the reason although my ... 
[differential-equations] [numerical-integration] [complex] [eigenvalues]
 

asked by ayman zayed https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=75518 Score of 1

9.16.3.3 Trying to use SetOptions on Style to set some default plotting options

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=284390

I want to set some default options for  Style . I tried this: 
... 
[formatting] [style] [text]
 

asked by Camillo https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=92529 Score of 1