circular polarizing filters

Tony_Reyes

Tony_Reyes

Well-known member
quick question:

if you are using one of these on a video camera will it still be effective when panning? or would you have to be rotating the filter relative to your pan?

and, what is a linear polarizing filter?

thanks in advance,
-tony
 
Hi Tony:

All Polarizers add their maximum polarizing effect at 90 degrees from the angle of the light source so if you are panning, yes, it's possible to see some variance, although if you are out in the sun, think about it, a pan would probably still leave your relative angle to the light source (the Sun) at about 90 degrees, right? Now a tilt, that's another story.

Linear and circular polarizers accomplish the same thing and either may be used on a manually focused camera. Linear polarizers can fool some autofocus systems though, especially on SLRs.

To make it even more confusing, circular polarizers are not always circular in shape. I have a Formatt 4x4" circular polarizer for my matte box. It's square, yet circular! As you may have guessed, circular is the filter's method of operation, not it's shape.

According to Wikipedia...
"A circular polarizer (sometimes called a CPL filter) similarly selects a linear state but then converts it to circularly polarized light, by adding a birefringent layer (typically a quarter-wave plate) to the filter after the linear polarizer. The metering and auto-focus sensors in certain cameras, including virtually all SLRs, will not work properly with linear polarizers, both because of the mirror and because of the beam-splitters used to split off the light for focusing and metering. Circular polarizers will work with all types of cameras."

You should spend lots of money and buy a good one, assuming you are shootng HD. The cheap ones like the Cokins are so/so, they work but have more internal reflections and distortions to your images than a really good one. I tink I paid about $300.00 for mine and I use it a lot.

Best,

Dan
 
thank you very much puredrifting.

that helps a lot. it also clears up the "rule of thumb" that they describe on the tiffen site. i've used polarizers for my DSLR and i LOVE it. it made me wonder why people don't use them more often.
this made me want to carryt his over to video (potentially HD). i wonder if it would be worth the investment??? i'm thinking the occasional shift in exposure would really mess with you and i'm wanting the look to be consistent. i know there are times where i'm really only panning a few degrees left and right (really subtle) but there are other times when i'm probably panning 120 degrees!

anyways, thanks for your response. it's making me think more.

-tony
 
Hi Tony:

Glad my post was helpful to you.

FWIW, I highly advise you to buy and use a polarizer whenever you need it. It will make your exteriors look much better. Also, I have NEVER had any issues with exposure varying just from the polarizer. Exposure usually needs to change as you pan anyway unless everything you are shooting has the exact same light levels and reflectance.

To successfully shoot exteriors, you need a polarizer, ND filters and ND grads. Everything else can be done in post/CC.

Dan
 
good point. i should have thought this through more. i'm thinking about the effects of the polarizer changing as i pan.

because don't you set it for a static shot and you can pan 45 degrees (roughly) left or right (equalling 90) and still have the same effects? but if you go outside of that 45 degrees your polarizer is unaffective and your image changes?? i'm pretty sure this is what i'm thinking about.
 
Tony_Reyes said:
good point. i should have thought this through more. i'm thinking about the effects of the polarizer changing as i pan.

because don't you set it for a static shot and you can pan 45 degrees (roughly) left or right (equalling 90) and still have the same effects? but if you go outside of that 45 degrees your polarizer is unaffective and your image changes?? i'm pretty sure this is what i'm thinking about.
Click to expand...

Tony:

Trust me, it is not that big of an issue. Cinematographers have been shooting with polarizers for decades and I have yet to see a first AC rotating a polarizer on a panning shot. You turn the polarizer to dial in the amount of the polarization desired, then you shoot. It's that simple. It is possible to over polarize a shot where the skies turn almost gray or black. All of this is also variable depending on the angle of the sun too. Polas are most obvious to use near high noon. As the afternoon wears on, the polarizing effect gradually minimizes because you are getting less than 90 degrees to the sun.

To me, it would be cutting off your nose to spite your face if you decided not to use a polarizer because you are afraid of inconsistency in your shot. If your shot looks like crap with washed out skies and reflections on water and glass but consistently looks like crap, is that better than the shot looking killer with blue skies, 3D-like clouds and saturated colors with some minor inconsistency in the polarizing effect? Keep in mind, these are not parameters you can change in post, it's either there in your captured image or not.

I think you are worrying about something that doesn't really factor into 99.976% of shoots.

Best,

Dan
 
SOLD!

good points. pretty sure i'm gonna go with a polarizer when the time comes.

thanks for you your time and info
 
I shoot a ton of nature, cloud and sunset stock footage and find a circular polarizer
indispensible. The only time you don't need it is when lighting is optimal, and how often does that happen? The lens gives the deep blue sky look that I need, something not easily done in post. I bought the Hoya Super HMC, a good mix of quality and reasonable price.
 
Only for minimizing reflections on glass or water. But they cut out around two stops so probably not very practical for indoor usage.

Dan
 
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