Topics

Linear vs circular polarizers?

John Tarver
 

Hey Y'all

I'm sure this has been covered, but what is the advantage of a circular polarizer vs linear?  When would you use one vs the other?  If you are building your own kit, which is the most useful if you can only buy one.

Asking for a friend ;)

John Tarver, csc
DP in even snowier Toronto

Florian Duning
 

Hi,

as far as I know you need circular polarizers when you want to rely on some autofocus mechanism or auto exposure. I think it has something to do with the interaction of linearily polarized light and mirrors found in DSLR cameras. Not sure if there are also issues with camera systems that don’t couple light into the exposure/focus sensor path by using a mirror.

A CPL filter is basically a linear polarizer with an added layer behind the filter to „swirl“ the light so it becomes unpolarized when it leaves the filter.

Best regards,

Florian Duning
DP based in Germany/Cologne



On 8. Feb 2018, at 16:07, John Tarver <johntdp@...> wrote:

Hey Y'all

I'm sure this has been covered, but what is the advantage of a circular polarizer vs linear?  When would you use one vs the other?  If you are building your own kit, which is the most useful if you can only buy one.

Asking for a friend ;)

John Tarver, csc
DP in even snowier Toronto

Daniel Gurzi
 

John,
There are a lot of articles that cover this actually. I spent a lot of time researching this as Abel Cine's Rental Manager back in the day and Mitch Gross and I used to have hour long conversations about it. So I feel your pain. 

I have it summed up in my head pretty simply. Polarizers compensate for reflections of light. A linear polarizer will block deflected light from a specific angle. So as you rotate that filter, you can change the source of reflections directly. Circular Polarizers are a more complex system that block out reflections from multiple angles at once. So typically you will get cleaner images through office windows and on water and such but you have to play around a bit more to find the exact position of the filter for the best result. 

There is a much more scientific explanation for all this, so I do apologize for the over simplification of a science. Dwight Lindsey at Lindsey Optics can probably give you a much more thorough answer. 


Daniel Gurzi
Biz Dev @ Kitsplit

Brooklyn, NY


On Thu, Feb 8, 2018 at 10:07 AM, John Tarver <johntdp@...> wrote:
Hey Y'all

I'm sure this has been covered, but what is the advantage of a circular polarizer vs linear?  When would you use one vs the other?  If you are building your own kit, which is the most useful if you can only buy one.

Asking for a friend ;)

John Tarver, csc
DP in even snowier Toronto

Mike Fecik
 

 

The only difference is that the circular polarizer includes a quarter wave retarder after the polarizer. If you only buy one, the circular is pretty much all purpose. The polarizer filter is used to block polarized light (Reflections are polarized, while ambient light is scattered) By rotating the filter so as to be cross axis to the polarized light (reflections) it will block them. As the rest of the light passes through the filter it becomes polarized. This now polarized light can sometimes be problematic for some systems particularly those using semi mirrored surfaces to read exposure. In this case you need a circular polarizer, that in effect will un-polarize the light passing through the filter. Having the quarter wave retarder and not needing it will cause no harm.

Mike Fecik

Tiffen Co.

 

From: cml-glass@... [mailto:cml-glass@...] On Behalf Of Daniel Gurzi
Sent: Thursday, February 08, 2018 11:05 AM
To: cml-glass@...
Subject: Re: [glass] Linear vs circular polarizers?

 

John,

There are a lot of articles that cover this actually. I spent a lot of time researching this as Abel Cine's Rental Manager back in the day and Mitch Gross and I used to have hour long conversations about it. So I feel your pain. 

 

I have it summed up in my head pretty simply. Polarizers compensate for reflections of light. A linear polarizer will block deflected light from a specific angle. So as you rotate that filter, you can change the source of reflections directly. Circular Polarizers are a more complex system that block out reflections from multiple angles at once. So typically you will get cleaner images through office windows and on water and such but you have to play around a bit more to find the exact position of the filter for the best result. 

 

There is a much more scientific explanation for all this, so I do apologize for the over simplification of a science. Dwight Lindsey at Lindsey Optics can probably give you a much more thorough answer. 

 


Daniel Gurzi
Biz Dev @ Kitsplit

Brooklyn, NY

 

On Thu, Feb 8, 2018 at 10:07 AM, John Tarver <johntdp@...> wrote:

Hey Y'all

I'm sure this has been covered, but what is the advantage of a circular polarizer vs linear?  When would you use one vs the other?  If you are building your own kit, which is the most useful if you can only buy one.

Asking for a friend ;)

John Tarver, csc
DP in even snowier Toronto

 

Mike Fecik
Laboratory Manager
T:631-609-3194
mfecik@...
www.tiffen.com

NOTICE:
The contents of this email and any attachments to it may contain privileged and confidential information from The Tiffen Company, LLC. This information is only for the viewing or use of the intended recipient. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution or use of, or the taking of any action in reliance upon, the information contained in this e-mail, or any of the attachments to this e-mail, is strictly prohibited and that this e-mail and all of the attachments to this e-mail, if any, must be immediately returned to The Tiffen Company, LLC or destroyed and, in either case, this e-mail and all attachments to this e-mail must be immediately deleted from your computer without making any copies hereof. If you have received this e-mail in error, please notify The Tiffen Company, LLC by e-mail immediately

Ira Tiffen
 

John: short answer—get a circular polarizer. It works in the same way as the linear, but does not have problems with certain internal camera and other optical systems. You can use it with most anything. The only drawbacks are that you need to know to mount it facing a certain way relative to the lens, and it costs a bit more than a linear.

 

Now some details:  A circular polarizer is a linear polarizer with an added component, a clear layer called a quarter-wave retarder. The retarder layer has to be on the side of the filter that faces the camera lens in order to work properly. The linear polarizer component of both filters is generally identical (for a given manufacturer) and as such performs the same functions within the image.

 

The polarizer, either circular or linear, allows management of polarized light in the scene. Effects include providing deeper blue sky and more dramatically white clouds; reducing or eliminating reflections from the surfaces of windows or water; increasing color saturation of certain objects in bright sunlight; and so on. The difference is that the circular polarizer, as mentioned earlier, actually serves to, in effect, depolarize the light after the polarizer layer has done its job for image management, and before the light enters the camera. This was initially offered years ago as a solution to the then-new auto-focus/auto-exposure cameras that bounced light off a partially silvered mirror, or beamsplitter, within the camera that directed some of the light to the sensor that determined exposure/focus. Since this reflected light is polarized, it will suffer adversely for having polarized light entering the camera system. Given the low chance that the light entering the system through the polarizer will be in the same polarization angle as the beamsplitter, since you have to rotate the polarizer according to what is required for each scene, the auto-focus/-exposure would likely not function as designed. The quarter-wave retarder effectively temporally corkscrews the linearly polarized light to eliminate the problem. Just be sure the circular polarizer is mounted with the retarder facing the lens. For round filters, this should be done by the manufacturer when the filter is placed in the ring (which only attaches one way). For square filters, the manufacturer will mark “This Side Out” on the glass so you know. If there is no marking for some reason, look through the filter and put the side facing the lens that is the side that through which you can see the polarization effects. The other side you won’t.

 

Hope this helps.

 

Ira Tiffen

PA, USA

 

 

 

Dwight Lindsey
 

John, Daniel:

 

The short answer is in fact that both Linear and Circular Polarizers do the same thing. The actual polarization effects such as reducing reflections on glass surfaces, increasing color saturation in foliage, darkening a blue sky . . . are the same with Linear and Circular.

 

In fact a Circular Polarizer contains a Linear Polarizer component.  It has a second layer inside the filter called a Quarter Wave Plate, which “spins” the light after it goes through the linear layer.

 

The linear polarizer element in the filter needs to be pointed at the world, with the quarter wave plate on the rear side, the camera lens side.  A circular polarizer doesn’t work if you get it in backwards.  With a screw-in filter that’s no issue.  With drop-in and rectangular filters for matte boxes, the filters are labeled with “this side out”.

 

One problem that the circular polarizer addresses is other reflective surfaces in your system.  The classic one in film was the video tap.  Using a linear polarizer on a film camera with a video tap, could and often would cause the video feed to go dark.

 

With a circular pol, the quarter wave plate on the rear of the polarizer spins the light so that the partial mirror in the video tap doesn’t cross polarize and block the light.  So if there are mirrors in your optical system, the circular pol solves any problems or potential problems.

 

If you have no mirrors in your system, such as video tap a DSLR mirror or a beam splitter . . . then the Linear-Pol will not cause you any trouble and you can’t put it in the matte box backwards, which might save you some time and trouble.

 

As an aside, I’m always amused that physicists describe light as a wave, when it’s convenient (colors and polarization). They describe it as a particle, when it’s convenient (photons, photo-electric solar panels).  When they speak quantum physics, things get really strange.

 

Dwight

 

Dwight Lindsey

President

Lindsey Optics, LLC

+1 661-522-7101 X102 (Office)

+1 818-634-1503 (Mobile)

www.lindseyoptics.com

 

Lindsey Optics horizontal logo 400 px wide

 

From: cml-glass@... [mailto:cml-glass@...] On Behalf Of Daniel Gurzi
Sent: Thursday, February 8, 2018 8:05 AM
To: cml-glass@...
Subject: Re: [glass] Linear vs circular polarizers?

 

John,

There are a lot of articles that cover this actually. I spent a lot of time researching this as Abel Cine's Rental Manager back in the day and Mitch Gross and I used to have hour long conversations about it. So I feel your pain. 

 

I have it summed up in my head pretty simply. Polarizers compensate for reflections of light. A linear polarizer will block deflected light from a specific angle. So as you rotate that filter, you can change the source of reflections directly. Circular Polarizers are a more complex system that block out reflections from multiple angles at once. So typically you will get cleaner images through office windows and on water and such but you have to play around a bit more to find the exact position of the filter for the best result. 

 

There is a much more scientific explanation for all this, so I do apologize for the over simplification of a science. Dwight Lindsey at Lindsey Optics can probably give you a much more thorough answer. 

 


Daniel Gurzi
Biz Dev @ Kitsplit

Brooklyn, NY

 

On Thu, Feb 8, 2018 at 10:07 AM, John Tarver <johntdp@...> wrote:

Hey Y'all

I'm sure this has been covered, but what is the advantage of a circular polarizer vs linear?  When would you use one vs the other?  If you are building your own kit, which is the most useful if you can only buy one.

Asking for a friend ;)

John Tarver, csc
DP in even snowier Toronto

 

Keith Putnam
 

This may be too specific a use-case but circular polarization is frequently found in stereography. When you're using a beam-splitter rig the beam-splitter mirror is itself a *linear* polarizer. This results in each camera receiving light with opposite polarization (one "eye', of course, seeing the light reflected by the beam splitter and the other "eye" seeing the light passing through the beam splitter). This leads to discrepancies which can become distracting artifacts when blending the two images. However, a way to reduce the discrepancy is to add a polarizing filter called a 1/4 wave retarder to the front of the mirror box. Linear polarization plus 1/4 wave polarization = circular polarization. With both "eyes" receiving light with more similar, though not identical, polarization discrepancies and therefore artifacts are reduced.

Keith Putnam
Local 600 DIT
New York City
 
On Thu, Feb 8, 2018 at 10:07 AM, John Tarver <johntdp@...> wrote:
 

I'm sure this has been covered, but what is the advantage of a circular polarizer vs linear?  When would you use one vs the other?

Mitch Gross
 

Now that the Filter Gods have chimed in I'll sum up in my best Jewish grandmother impersonation. Buy a circular pola; like chicken soup, it couldn't hurt.

Also, invest in the more expensive heavier duty variants, like the Tru-Pol or the Ultra-Pol. Far better polarizing effect with greater saturations of color. You get more of what you want a pola for.


Mitch Gross
Cinema Product Manager
Panasonic Media Entertainment Company
New York

Argyris_Theos_cml
 

As already mentioned, the retarder is not a polarizer. You could for practical purposes think of it as a "de-polarizer", but keep in mind : this is not exactly correct.
Polarized light does not exist only after our filters. There is lots of it everywhere we look at. In conventional photography we may need to eliminate a reflection or darken a sky, so we use a polarizer to cross angles with the already polarized light and eliminate it.
But, as already mentioned, sometimes in camera systems there are polarizing "devices" (e.g. a semi silvered mirror) that will give unexpected/unwanted results. So the idea is to "translate" the light into something this "device" will not interfere with, aka "depolarized" light. So we place the retarder after the filter and before this "device" (and the factories bond them as one filter, the C-pol). In film cameras (movie or SLR's) the "device" was placed behind the lens.
But in stereography the "device" is found in front of the lens. It is the semi silvered mirror that acts as the beam splitter. Being a polarizer by definition this mirror will send unequal parts of the incoming polarized light to each camera (but retain the 50/50 ratio for unpolarized light) . So a blue sky might show darker in one of the two images. To cure this we make certain that the light hitting the beam splitter is not polarized by adding the retarder in front of the system.
Of course this has other issues, like flare and needs extreme cleaning.

This was a long post and not 100% within the forums limits, my apologies
Best

Argyris Theos, gsc
DoP, Athens Greece,
theos@...
+306944725315
Skype Argyris.Theos
www.vimeo.com/argyristheos
via iPhone

8 Φεβ 2018, 7:34 μ.μ., ο/η "Keith Putnam" <keith@...> έγραψε:

add a polarizing filter called a 1/4 wave retarder

Dwight Lindsey
 

Also . . . with a better polarizer you can always select less polarization, by adjusting the rotation of the filter.

 

You may well want to remove enough reflection that you can see through the window or windshield, but not so much that the glass disappears . . .

 

With a better polarizer, you have more creative control.

 

Dwight

 

Dwight Lindsey

President

Lindsey Optics, LLC

+1 661-522-7101 X102 (Office)

+1 818-634-1503 (Mobile)

www.lindseyoptics.com

 

Lindsey Optics horizontal logo 400 px wide

 

 

Mako Koiwai
 

I always found it useful to have One Stop Polas in my kit … low light pola. Less effect … less light loss. Good for controlling facial sheen.

makofoto, s. pasadena, ca

Dwight Lindsey
 

While we’re on the subject of reducing reflections with polarizers, I’d like to say that it has always struck me as odd that we use uncoated filters in cinematography. 

 

For as long as anyone can recall, small round screw-in filters for photography have had good multi-layer anti-reflection coating (MC coating).

 

Yet we make big budget movies with uncoated filter glass.

 

You can get as much as 4% reflection per surface on flat glass.  That’s 8% per filter (2 sides).  If you have just two filters in your matte box, 16% of the light entering your system is going somewhere unintended . . . reducing contrast and color saturation.  It’s “stray light” or flare.

 

Why use a great lens to increase image quality and then screw it up with uncoated filters?

 

Of course if you’re after that “vintage look” . . .

 

Dwight

 

Dwight Lindsey

President

Lindsey Optics, LLC

+1 661-522-7101 X102 (Office)

+1 818-634-1503 (Mobile)

www.lindseyoptics.com

 

Lindsey Optics horizontal logo 400 px wide

 

_._,_._,_

Jay Holben
 

Dwight -

This has bothered me for some time. I have made this inquiry of both Tiffen and Schneider and the response was the same both times - "we certainly could coat filters, but there has never been a demand to do so. If there was high enough demand, we'd do it."

I think this deserves a bit of education for cinematographers on the benefits of coated filters and a request for the major filter manufacturers. I'd be curious what the cost difference would be for micro film deposited coating on filters as opposed to uncoated - and also how many cinematographers see the value and would request/demand this as an option?

Personally - even if you're looking for that "vintage" look - I see no benefit in NOT coating filters. Allow the coating/lack thereof on the lens to dictate the look not the reflections from a filter. Or, at worst, allow cinematographers the choice in coated/uncoated options.
Jay Holben
Director/Producer
Co-Chair Lens Committee, ASC Motion Imaging Technology Council
Adakin Productions
Los Angeles, CA
www.jayholben.com
Instagram @jayholben
On 2/9/2018 12:57 PM, Dwight Lindsey wrote:

While we’re on the subject of reducing reflections with polarizers, I’d like to say that it has always struck me as odd that we use uncoated filters in cinematography. 

 

For as long as anyone can recall, small round screw-in filters for photography have had good multi-layer anti-reflection coating (MC coating).

 


 

Dwight

 

Dwight Lindsey

President

Lindsey Optics, LLC


Dwight Lindsey
 

Jay:

 

I was CEO of Schneider Optics until I left Schneider a year ago to found my own company.

 

I tried a number of times to get my team at Schneider Optics to do AR coating and I always failed to get it done.  I got the same answer as you report.

 

Now that I have my own company, with a much smaller team, I feel able to just decide to do it, without any need to “encourage” the team.

 

We’re just doing it, and the filters don’t cost more with the AR coating.

 

We’re also putting a serial number on every filter.  So we’ll know who we sold it to and when we sold it.  I suppose this might also be useful to rental houses.

 

Dwight

 

Dwight Lindsey

President

Lindsey Optics, LLC

+1 661-522-7101 X102 (Office)

+1 818-634-1503 (Mobile)

www.lindseyoptics.com

 

Lindsey Optics horizontal logo 400 px wide

 

 

 

Dwight -

This has bothered me for some time. I have made this inquiry of both Tiffen and Schneider and the response was the same both times - "we certainly could coat filters, but there has never been a demand to do so. If there was high enough demand, we'd do it."


 

Leonard Levy
 


On Feb 8, 2018, at 8:09 PM, Mitch Gross <mitchgrosscml@...> wrote:
Also, invest in the more expensive heavier duty variants, like the Tru-Pol or the Ultra-Pol. Far better polarizing effect with greater saturations of color. You get more of what you want a pola for.

Wow Dont know where Ive been but I never knew there were better polarizers - just thought they were all the same . What about Kaeseman polarizers, what the heck are those anyway? Good or Bad?

Leonard Levy, DP
San Rafael, CA








Dwight Lindsey
 

Kaesemann is a brand name, owned by Schneider.  There was a Kaesemann company, which was purchased by Schneider quite some time ago.  Kaesmann was famous for high quality polarizers and Schneider has maintained the high quality level for the brand. When I was with Schneider, Kaesamann was only available in small round screw-in filters.  I believe that’s still true

 

On the square, rectangular and cine round filter front:  Many years ago, we at Schneider introduced the True-Pol polarizers in linear and circular.  They were, in my opinion, better than the currently available product for cine matte boxes. Tiffen then matched us with the Ultra-Pol, which is, in my opinion, equivalent.

 

Polarizers have tiny parallel lines which pass light polarized in one direction and clip light with other polarizations.  When the lines are closer together, the polarization is better . . . and the transmission is less. So as manufacturers, we need to choose between better polarization and better transmission.

 

Dwight Lindsey

President

Lindsey Optics, LLC

+1 661-522-7101 X102 (Office)

+1 818-634-1503 (Mobile)

www.lindseyoptics.com

 

Lindsey Optics horizontal logo 400 px wide

 



Wow Dont know where Ive been but I never knew there were better polarizers - just thought they were all the same . What about Kaeseman polarizers, what the heck are those anyway? Good or Bad?



Leonard Levy, DP

San Rafael, CA



 

 

 

 

 

 

Leonard Levy
 

On Feb 9, 2018, at 10:56 PM, Dwight Lindsey <dwight@...> wrote:
Kaesemann is a brand name, owned by Schneider.  There was a Kaesemann company, which was purchased by Schneider quite some time ago.  Kaesmann was famous for high quality polarizers and Schneider has maintained the high quality level for the brand. When I was with Schneider, Kaesamann was only available in small round screw-in filters.  I believe that’s still true...Polarizers have tiny parallel lines which pass light polarized in one direction and clip light with other polarizations.  When the lines are closer together, the polarization is better . . . and the transmission is less. So as manufacturers, we need to choose between better polarization and better transmission

Interesting - Thanks for that info. I recently bought a circular Kaeseman polarizer from B+W or Schneider and to my eye it looked to have lower contrast and less saturated blue skies than my other polarizers. But when I tested it on a video camera the results were identical.  I couldn’t make sense of that but  it seems to function fine. 
Does that make any sense to you filter experts out there?

Leonard Levy, DP
San Rafael, CA






Mako Koiwai
 


Kaesemann is a brand name, owned by Schneider. There was a Kaesemann company, which was purchased by Schneider quite some time ago. Kaesmann was famous for high quality polarizers and Schneider has maintained the high quality level for the brand.


************************************


A number of years ago I bought a Canon 100/400 still zoom. It wasn’t very sharp at 400 mm. I realized it was because I was using the basic Canon Pola filter on it. I found that B+W offered an Ultra THIN Kaesmann Pola filter, designed especially for long lenses. Fairly expensive … if I recall $275 for a 77 mm filter … 11 years ago … but it made all the difference in the world!

There must not be a market for it because I recently tried to find it in another size and could not locate one, Dwight.



makofoto, s. pasadena, ca

Dwight Lindsey
 

Mako:

 

I don’t personally recall an ultra thin Kaesemann polarizer from my time at Schneider.  I don’t doubt that it existed and may still exist, it’s just that the B+W product range is HUGE.

 

If it’s still of interest, I suggest you call Kevin in the New York Schneider Optics office, he knows everything about the Schneider B+W and Kaesemann filter product range.

 

I don’t imagine that the thickness or thinness of the filter was the primary problem or solution.  For long lenses filters really need to be flat within fractions of a wavelength of light.  You can test that either with a laser interferometer in a lab . . . or as you did in a more practical way, by putting the filter on a long lens and observing the difference between sharpness with no filter and sharpness with the filter in place.

 

Our Zygo Phase Shift  laser interferometer is available to members of this list.  Feel free to bring a filter or filters to our shop North of Los Angeles, or send them to us.

 

A very flat filter with good surface quality (scratch/dig) and an AR coating, won’t have a negative effect on image quality with long lenses, even if its not “ultra thin”.  BTW, normal small round screw-in filters are often 2mm thick.  Round drop-in filters in 138mm and 4.5” by the major manufacturers, and us newbies, are usually 3.43mm thick.

 

Dwight

 

Dwight Lindsey

President

Lindsey Optics, LLC

+1 661-522-7101 X102 (Office)

+1 818-634-1503 (Mobile)

www.lindseyoptics.com

 

Lindsey Optics horizontal logo 400 px wide

 


A number of years ago I bought a Canon 100/400 still zoom. It wasn’t very sharp at 400 mm. I realized it was because I was using the basic Canon Pola filter on it. I found that B+W offered an Ultra THIN Kaesmann Pola filter, designed especially for long lenses. Fairly expensive … if I recall $275 for a 77 mm filter … 11 years ago … but it made all the difference in the world!

There must not be a market for it because I recently tried to find it in another size and could not locate one, Dwight.

 

Simon Temple
 

Wow there are some pola scientists out there!  Buy both! Then you have a variable ND by stacking the two together (i put my Tru-Pol in a Rota Pola stage) and then a linear up front with a thumbwheel on top of the Rota stage to vary the ND.  Switch the linear around and you have a cool/warm variable filter.
Occasionally I've had to watch for some funky patterns in hot spots at deeper amounts of ND, and internal reflections between filters, but its a winning combination IMO….

Apologies to you Cine scientists out there as this is a deviation away from the Linear vs Circular discussion, but worth a mention!

Simon Temple
cameraman NZ

On 9 Feb 2018, at 17:09, Mitch Gross <mitchgrosscml@...> wrote:

Now that the Filter Gods have chimed in I'll sum up in my best Jewish grandmother impersonation. Buy a circular pola; like chicken soup, it couldn't hurt.

Also, invest in the more expensive heavier duty variants, like the Tru-Pol or the Ultra-Pol. Far better polarizing effect with greater saturations of color. You get more of what you want a pola for.


Mitch Gross
Cinema Product Manager
Panasonic Media Entertainment Company
New York