Light Pollution Filter - Image Distortion

[Grumman]

Hello,

 

I have a Canon 100D (non modified) DSLR on my Sky-Watcher 72ED without a FF (I am planning to buy one in the coming months).

I recently bought a Astronomik CLS-CCD clip-on filter for my camera and I have noticed in the photos that the edge stars are more distorted if I have the filter on.

I recently found a software called CCD Inspector and it analyses the photo and give out a 3D graph of the image field.

I have loaded two shots one with the filter on and one without. It seems that the filter has a flattening effect on the edge of the photos pushing stars even more out-of focus in the middle of the photo... 

I was wondering, If I get a FF for my scope, will this effect get worse or will it be leveled-out?

 

 

NO FF, NO CLS-CCD Filter 

 

NO FF, WITH CLS-CCD Filter