Square or screw on polariser?

[AliB89]

Hi there,

I have established that I need a circular polariser, however I am unsure whether to get a square filter to use with a holder, or a screw on type filter which seem to be more common.

I am looking to use the polariser with both my Canon 18-55mm and 50mm f1.8, and I already own a Cokin filter holder with filter rings for both lenses.

Obviously with the screw on filters I would need to purchase two, one for each lens, and with the square filters I would only have to buy one. Any other things I need to consider or opinions on this??

Also when using a combination of a polariser and a ND Grad filter would this affect my decision? When using square filters presumably it would not be possible to rotate each one freely with respect to each other, is this a problem? And presumably a screw on filter would not work with the filter holder??

Thanks in advance

Ali

[Skoropada]

Hi AliB89,

I own a Cokin circular polarizer and that filter is indeed round, and can be rotated inside the holder independently of any other square filter you may have.

[Doug Sundseth]

Originally Posted by AliB89

Obviously with the screw on filters I would need to purchase two, one for each lens, and with the square filters I would only have to buy one. Any other things I need to consider or opinions on this??

That's less obvious than you think. You can alternatively buy a filter to fit the larger lens (or the largest lens you plan to buy) and then buy step down rings to fit the lenses requiring smaller filters.

You'll want to think about what sort of coating the various filters have. More expensive filters are coated to reduce internal reflection (and thus lens flare and reflection artifacts on images).

You'll want to consider the quality of the glass (preferably) or other substance used to make the filter. Better filters will degrade your images less.

Finally, you should consider whether you will want to be using a lens hood with the filters. Both square filter holders and step down rings make it difficult or impossible to use lens hoods. In direct sunlight you will sometimes need to shade the lens/filter to prevent artifacts.

The lens hood issue was a major consideration for me, as I live in the western US, where the sun is hard, bright, and visible most of the time. If you plan to shoot in the dark or when it's cloudy most/much of the time, this might be less important to you.

Originally Posted by AliB89

Also when using a combination of a polariser and a ND Grad filter would this affect my decision? When using square filters presumably it would not be possible to rotate each one freely with respect to each other, is this a problem? And presumably a screw on filter would not work with the filter holder??

You will often want to adjust the angle of polarizer and ND Grad separately.

You should be able to attach the filter rings to the screw in filter as long as you don't get a slim-mount filter. Normal screw-in filters have male threads on the camera side and female threads on the subject side to allow filter stacking. These threads are the same as the filter threads on the front of the lens.