# Polarizer issue??



## drob (Jul 15, 2016)

Was at Rainier yesterday and had an issue with my polarizer. Didn't realize it until I got home, it was just this series at Reflection Lake, after sunrise, light coming from my right. It's a new circular polarizer filter, not super cheap but not super expensive. It's a PROMASTER 77mm on my 16-35 f 4 IS. I've never encounter this with my previous circ polarizer. Any thoughts?


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## neuroanatomist (Jul 15, 2016)

I presume the 'issue' to which you're referring is the uneven polatization of the sky? That's what happens when you put a polarizer on an ultrawide lens. The angle of the sun relative to your image plane determines the amount of polarization, and thus the angle of polarization varies continuously with the angle from the sun. So, with a lens wider than about 28mm (on FF) the sky will be unevenly polarized (and as you see in your shot, that unevenness due to the wide FoV also applies to reducing reflections). You can use the effect creatively, or skip the polarizer for those shots if it bothers you.

Side note: I just mentioned – literally, a few minutes ago – the issue I see in your example in the thread on Lee filters for the 11-24L. 

BTW, Promaster filters aren't the greatest. Personally, I'd go with a B+W Käsemann CPL or a high-end Hoya CPL for use with a very sharp lens like the 16-35/4L IS. Promaster filters are cheaper than you might think at least in terms of production cost, they are so prevalent in retail camera shops because they get marked up by a substantial amount, meaning good profit for the store.


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## ahsanford (Jul 15, 2016)

neuroanatomist said:


> I presume the 'issue' to which you're referring is the uneven polatization of the sky? That's what happens when you put a polarizer on an ultrawide lens. The angle of the sun relative to your image plane determines the amount of polarization, and thus the angle of polarization varies continuously with the angle from the sun. So, with a lens wider than about 28mm (on FF) the sky will be unevenly polarized (and as you see in your shot, that unevenness due to the wide FoV also applies to reducing reflections). You can use the effect creatively, or skip the polarizer for those shots if it bothers you.
> 
> Side note: I just mentioned – literally, a few minutes ago – the issue I see in your example in the thread on Lee filters for the 11-24L.
> 
> BTW, Promaster filters aren't the greatest. Personally, I'd go with a B+W Käsemann CPL or a high-end Hoya CPL for use with a very sharp lens like the 16-35/4L IS. Promaster filters are cheaper than you might think at least in terms of production cost, they are so prevalent in retail camera shops because they get marked up by a substantial amount, meaning good profit for the store.



+1 on the B+W. That's all I use for my thread-in filters.

- A


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## drob (Jul 16, 2016)

Hey, thanks for the response. Makes sense. i purchased the promaster while on vacation after breaking my other filter. It was the only when they had so I was slightly desperate. I've seen the uneven polarization with the other but never this extreme. Again, thanks.


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