You don't need circular polarizer for the F717. Circular is
generally required for SLR because of the mirror in the SLR.
For the F717, get yourself a Linear Polarizer and save money. My
Hoya Multicoated (HMC) polarizer has threaded front and its
relatively good.
I have used circular polarizers since 1973 photographing thru SLR
cameras and now thru Sony 717. There is nothing about an SLR
mirror that requires anything special. The view thru my SLR and
my Sony are the same. When you view a "shot" you have set up, say
an auto or some landscape, and you view thru the SLR and or the
Sony 717, and then rotate the polarizer while viewing thru either
camera, you will notice the change in the amount of reflections
from the auto glass and or reflections from the folage in the
landscape.
A Linear is just that. It works in one "plane" only. A rotating
polarizer is able to rotate two together so that it can adjust the
view exactly the way the photographer wants it. A linear will
work for general snap shots but you will notice that professionals
use rotating polarizers.
There is a difference between the two in cost. There is a reason
the rotating version cost more. It will do more for the
photographer.
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kr616