'slim' or normal polariser on 21mm lens?

[suselko]

Hi guys!
I'm planning to buy a B+W polariser filter but am not sure if I need a 'slim' one or a normal one for my 21mm lens. In the filter description it says that 'slim' is necessary for 20 or 18 mm lenses, so shall I treat it literally and not bother as 21 is not 20, or maybe I should bother?
Many thanks
Filip

 

[RML]

I'd go for the slim one.

 

[RF-Addict]

Definetely the slim filter - what have you got to lose?

 

[suselko]

Thank you for useful comments - I'm going for the slim then, F

 

[Sparrow]

Polarising filters on very wide lenses can be a bit unpredictable; the changes in the natural polarisation of the sky over such a wide FOV will almost certainly cause some variation in exposure across the frame