polorizing filter
 

Does anyone use a Polorizing filters? Do they make much difference? What about a Spherical Polorizing filter?

Thanks.

Yes, they are very useful and do make a difference. Use the 'Search" button and you'll locate many, many posts on the subject. BTW, I think that you meant "circular" polarizer, not "spherical".

What Ken said. Although I've never had the need for mine, there is comfort in knowing its there in my camera bag if I need it.

(ooops)
 

thanks.

I had tried a search and came up with nothing...but I had spelled polarizing wrong. :(

Dylan,

Try shooting with it. It makes the colors more sturated or vibrant. You want deep blue skies, that's one way get them. It does a whole lot more than just take glare off of glass.

Jeff

Jeff, I have used it outdoors for skies. I meant that I've never needed it for it's glare/reflection reduction. I should have been a little more clear, since it is a two purpose item.
It does do a really nice job bringing out the blue in the sky.

I "audition" a polarizer for many situations working outside, some of which are not obvious reflection issues. We all know that they do a fantastic job of removing reflections in glass when shot at a 45 degree angle (i.e. perfect for windshields, not so great for side windows of a car), but they can also help tremendously when dealing with high contrast exteriors such as shooting down a street with the sun in front of you (backlit). In this instance, a certain amount of the brightness of the street itself may be due to glare and the polarizer will knock down the intensity, helping achieve a less hot image. Likewise shooting around water, it can help bring the bright white appearance down to a more photographable blue/green. Too much polarization can deaden an image, so it's good to think of a polarizer as not just an "on-off" filter, but something that allows one to dial in exactly as much effect as desired. Going back to that windshield, it may be nice to see a little reflection of the exterior world (trees, puffy clouds in sky etc) so a partial polarization may work great. It's often helpful to hold the pola up to your eye and rotate it, watching the effect, then once the desired angle is found you transfer it to the camera at that angle.

It is also cool as a sort of ND filter when you don't want the 7 stops knocked off that the XL-1 (if you have one) does for you.

Yes Dan, good point. Most polas will cut between 1 2/3 and 2 stops of light.

I may sometimes use an UltraPol on a subject to saturate skin tone and allow me to open up the iris which can sometimes help to throw the background out of focus. It's also a handy filter to knock out shiny reflections on people's faces when there is not makeup available.

In what situations would you use a circular polarized filter as opposed to a "regular" one?

Circular polarizer offer a stronger affect than linear polarizers. Blue skies bluer, green grass greener etc. Some cameras may also require the circular type to avoid interference with auto focus or other performence related factors. There are strong arguments on both sides as to if they are required or not. Circular polarizers are also more expensive. Inexpensive polarizers sometimes don't even work. Try it before you be sure of the stores return policy. I recommend B + W, Heliopan and Nikon as better circular polarizers. Tiffen, Hoya and other name brands are in a lower tier in my opinion.

Jeff

Jeff:

I have understood that circular polarizer are designed for cameras that incorporate a beam splitter or light meter/auto-focus system that may be fooled by the polarized light, and they essentially depolarize the transmitted light after the initial polarization. In other words, they don't create any more effect than a linear polarizer...?

Incidentally, Tiffen has introduced a stronger pola (Ultra-Pol) to compete with the Tru-pol from B&W/Schneider. It's definitely more potent than their earlier offering.

The Tiffen Water White UltraPol compares easily and very favorably with the B&W TruePol. It is being used on many sets now, in addition to many other Tiffen filters - at least that is what is being reported by shooters out in the Burbank and Hollywood area,,, not as clear what the filter of choice is from "the other Hollywood" on the other side of the country, not as many reports coming in from there.

Due to the big demand for the UltraPol, Tiffen has decided to make it available as a screw-on filter.

I have some B&W filters as well and I like them a lot, in addition to some Schneider filters which I like as well, and I would not hesitate to lump my Tiffen filters into that same category.

Over the years I've done side by side film tests with linear and circular polarizers. One test was to evaluate the reduction of reflection from glass. The circular polarizer clearly reduced the amount of reflection over the linear in that test. Since the affect of saturating colors comes from reducing the polarized light reflected off grass, buildings etc. it could be assumed that the affect would be noticeable in all scenes. The tests I did of average scenes involved exposing 35mm slide film and using the same exposure, just switching filters. The test slides show an increase in saturation from linear to circular. However, the tests were subjective in that the sampling of filters was too small and densitometer readings were not made of the slides. If it's not a difference between polarizers what could cause the affect? The circular polarizer my require a higher filter factor. It could reduce exposure maybe a 1/3 of a stop and the manual exposure setting did not compensate for the factor. The exposure change of 1/3 stop less light could saturate the colors in the slides. If I have time in the next month or so I may repeat the test a little more objectively. However, the comparison of reflections on glass are clearly superior with a circular polarizer.

Jeff

Jeff, I am certainly surprised to hear this...I have NEVER seen a circular pola in use on a film set & if in fact it did provide a more significant amount of polarization, that would be a powerful discovery. I would personally be more interested in the application of flare reduction (backlit sun on street etc) and deepening the effect on skies that are not exactly 90 degrees from the sun, and if a circular pola delivers, cool.

As it is, I'm sort of confused why most of the users here (on the DVinfo.net) who post about polarizers have brought up the circular version. The only thing I can imagine is that camera stores who are used to recommending them to their still camera users take it upon themselves to urge their video camera buyers to go with that version as well, when a linear pola should suffice. Anyone care to comment on where they have "heard" that they should be using circular polas?

Some motion picture cameras would require circular polarizers. Cameras that use beam splitters for video assist would create polarized light. A linear polarizer would darken part of the video image. So, in theory any camera that uses beam splitters or semi-transparent mirrors would require circular polarizers.

I know there is an efficiency rating for polarizers and I believe it is based on the amount of polarized light (reflection?) blocked. Circular polarizers, depending on quality, have higher efficiency ratings. Polarizers also work on certain frequencies (color) of light. I seem to recall that polarizers for photography work mostly in the yellows. If I'm remembering this right, it might affect the metering of scenes with certain predominant colors.

Acording to the Tiffen site, a circular polarizer is a linear polarizer with a 1/4 wave retarder tacked onto it's back side.

Bryan, you are correct. Circular polarizers contain a linear polarizer and the 1/4 wave retarder (Germans call them foils). The retarder is oriented 45 degrees in respect to the linear polarizers axis. The retarder causes the linear polarized light to rotate. Depending on the construction of the retarder, light will rotate either left or right in a circular motion.

Linear polarizers (part of the circular design) have slots or palings that allow light that is parallel to the slot to pass through. Other light is rejected. The more slots (narrower construction) the higher the efficiency and the less reflection. Of course the less light that passes through the greater the filter factor.

Circular polarizers may aid in two ways. Several manufactures claim the glass used in CP are planned flatter for use with telephotos. This flatter glass does not change the focal length of the lens (which would change DOF charts) or cause increased optical defects (more noticeable with a telephoto). The retarder helps reduce internal reflection (flare) and prevents a reduction in contrast.

Most manufactures don't rate the efficiency of their polarizers (too embarrassed?) but those few that do, show a slightly higher efficiency for the CP. Is it enough to see a difference in performance? I think so based on previous tests (film based). I'm not sure if the differences would show in video. I may try testing this in the next few months.

Jeff

The best way to comparatively test the ER (extinction ratio) of polars is to take two of them, put them over each other on a (strong) white lightsource (if circ polars, the retarders have to be at the outer sides) and veryfy (measure) how dark you can get the crossed polars. Good polars will get uniformly very dark and remain colorless. It can be verified that the very high attenuations are very, very rotation angle dependant (fractions of degrees) Checking/comparing the performances on a camera would be very difficult for getting reliable results. The ER and suppression angle is a very big issue in LCD projector technology for getting high contrast ratio's.
Beamsplitters or other parts in videocams don't polarize in their active zones so they don't need circ polars.

continued......
 

Back to the original question……..

For those few of us who stand in rivers, or have the tripod’s setup just out of the water while shooting footage all day……

You never will see the circular polarized filter being taken off the end of my telephoto lens during daylight hours where the sun is above the horizon. In the Alaskan summers, that can be quite a long time <;~)

Water shots of fish are absolutely amazing if the rivers are “gin clear” to start with. Some of the best non-action type of footage we shot this past summer, is of various types of Salmon in their natural habitat.

You’ll also generally notice that any serious fisherman has them on their head mounted lens………in the form of polarized sunglasses. If your not into fishing, watch a fishing show on Saturday mornings and observe the plethora of polarization.