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View Full Version : Linear Polarizer vs Circular Polarizer: What's the diff?



Anex
11-18-2004, 01:07 PM
Hi, could you shed some light on what the difference is between Linear and Circular Polarizers? I've read the manufactures stated difference (i.e. circular = auto focus cams, linear = manual focus cams) but that really doesn't help much. Would one (or more) of you be able to provide a little more understandable/useful explanation?

As always, your help is much appreciated.

genece
11-18-2004, 02:50 PM
Copied from Luminous-Landscape

There are two types of polarizing filters available linear or circular. Linear polarizers are more effective and less expensive than circular ones. But circular polarizers are needed with just about any camera that has a through-the-lens metering system, or autofocus.

The reason for this is that both of these systems use semi-silvered mirrors to siphon off some of the light coming though the lens. If that light is linearly polarized it renders either the metering or the autofocus ineffective. This means that you're going to have to buy circular polarizers unless you're shooting with a pre-1970's camera, or a view camera.

The FZ series cameras work just fine with a linear polarizer

Anex
11-18-2004, 03:00 PM
Would you or anyone have sample pics of what a linear polarizer looks like in comparision to a circular one - pics of scenary, not the filters themselves of course :)

From my additional searching, it seems that Circular is mainly for high ends digitals; though they also say, when in doubt, get circular.

Thanks for the info Genece, much appreciated.

HawkeyeLonewolf
11-18-2004, 05:34 PM
Funny thing is, I bought a UV filter on ebay for protection and it came WITH a Circular Polarizer. :) Sold as a set.

Didn't know that I'd gotten something good until I started reading up on what it could do :)

amitoufu
11-20-2004, 02:57 AM
Hi Genece,

Do you mean that Circular Polarizer lens doesn't work with FZ20 or because Linear Polarizer lens is cheaper that why you suggest the Linear instead of the Circular?

Thanks

genece
11-20-2004, 06:02 AM
Just cheaper thats all... either works just fine.
I have a 55mm circular for my FZ10 and a 62 mm linear on the FZ20.

PixChick
11-20-2004, 06:15 AM
Just cheaper thats all... either works just fine.
I have a 55mm circular for my FZ10 and a 62 mm linear on the FZ20.


Well, I am not an expert in this field or anything but I figured I'd throw in my 2cents anyhow...

I have been reading up a bit on polarizers 'cuz I want to get one very soon. I have read a few posts that say there is only a small difference in the quality you get with linear vs circular (but I have read the opposite as well, so who knows which is true??). But one thing that made me reconsider getting the linear was this: if I choose to upgrade at some point and get a different cam, I might not be able to use the linear polarizer on it. Then I need a new one. Maybe not a big deal to some, but worth considering.

Jim Last
11-20-2004, 08:03 AM
A circular polarizing filter is for use with all cameras with beam splitters in the light paths of their TTL exposure meter and with autofocus lenses.

A Linear polarization filter is for SLRs and rangefinder cameras without beam splitters in their light paths.

Circular polarization has the same pictorial effect as linear polarization, but allows for proper exposure metering and/or autofocus distance settings.


Polarizers are multi-talented
Experienced photographers consider po-larizing filters to be the most important filters. Their ability to reduce or eliminate reflections is probably their best-known feature, but it is not the only one. They enhance the color purity of the subject (increased color saturation) by blocking the blue veil of light from the sky, They increase the contrast in black-and-white photographs, reduce haze, and make white clouds stand out dramatically from an intensely blue sky. When the filter is rotated by 90 from its normal reflection-reducing position, it can even appear to increase the relative intensity of reflec-tions on water, glass, lacquer and plastic materials up to a factor of 2. B&W Filter Handbook


With polarizing filters, reflections on glass, lacquer, on nearly all plastic materials and other electrically non-conducting surfaces can often be reduced or even eliminated. Polarizing Filters provide you the control over how much reflection you wish to remain because the light reflected at an angle of about 40 to 70 by these surfaces is strongly polarized. Its transmission can be reduced, blocked or even enhanced! In relation to the re-maining unpolarized light, depending on the rota-tion of the filter. Thus a clear view is made possible through plates of glass, of goldfish below the sur-face of the water, or of writing or pictures behind a glossy layer of lacquer.
Every object outdoors reflects light from the sky more or less diffusely and largely polarized, some objects, such as green plants and red roof tiles are covered by a bluish-gray veil that can make them appear pale and dirty. Polarizing Filters can remove this polarized veil and thus increase the saturation of the true color. Because the blue light from the sky, especially at an angle approximately perpendicular to the sun is strongly polarized, a polarizing filter can be used to render the sky with a more saturated color, so that white clouds will stand out more dramatically. B&W Filter Handbook

amitoufu
11-20-2004, 10:52 AM
Thanks for everyone's 2cents. I always think that Panasonic should give you guys commission. I almost bought a Canon D300 when I was going to replace my Canon A75. Just before I placed order, I found this Forums and I bought my Panasonic FZ20 2 weeks ago. I believe a lot of people did the same thing too. I still explorering my FZ20 and hopefully with you guys help I will become an expert of my new camera. :)

Jim Last
11-20-2004, 04:28 PM
Everyone must remember that the best way is to see if any camera suits your requirements, then get your hands on one for a trial, at the end of the day it is you that has to use the camera not us :)

manxman
11-29-2004, 09:22 PM
Jim,

After reading your comments as well as the other posts, I find myself still confused about which polarizing filter to choose. I have read a number of times in this forum and in others that either one-circular or linear-will work just fine. Is this your understanding as well, or do you recommend one over the other, and experientially, why? Thanks for your input. :confused:

Jim Last
11-30-2004, 12:52 AM
There is no difference in the quality of a Circular and Linear polariser they are essentially the same filter. Both are in fact linear filters however the difference between them is the Circular Polariser has a second filter layer behind the Polariser which scatters a small amount of light to help the autofocus system work. This is because linear light has very little contrast to it.

If in doubt always use a circular polariser as this will work on both manual and auto focus whereas a linear will only work in manual.

Baz from Ephotozine (http://www.ephotozine.com/forum/viewanswers.cfm?qid=6785)

This may help.

christ0ph
11-30-2004, 08:33 AM
I see. The use of this term is confusing, because in radio, there really is "circular polarization", and it requires handedness as well. So, a circularly polarized radio wave will require a similar antenna on both transmitting and receiving ends. (they typically are helical)

The two 'senses' cancel out.

manxman
11-30-2004, 03:15 PM
Greetings to the Panasonic forum members,

I have been reading posts about polarising filters for days now on a number of different sites. I have been confused inspite of so much good information.
Today it dawned on me to go into our local camera store and consult with some guys who love photography and have been using and selling camera equipment for a couple decades or more.

This is what I have found out. The man I was speaking with I have known for 20 years. He said get the CIRCULAR POLARISING FILTER because the auto focus mechanism will not read light correctly through a linear filter. He said he has tried a linear filter on a few of the different cameras in the shop-including his own high end digiital-and has had poor results when using the linear filter. When he switched to the circular and tested the cameras again, his pictures were as expected. Clear, good color and exposure, etc. Also he said that the Circular filter can be used on a slr camera.

"So why are people still buying linear filters?" I asked.
"They are less expensive to produce and buy," he answered.

I cannot speak to a few of the comments I have read from some members who said they use the Linear Polariser on their FZ20,s, but I refuse to be further perplexed by those comments.

Having said all this, I have finally made my decision, and am now ordering a Circular Polarising filter. This is the end of my story, investigation, and confusion. Hope somehow this helps . :)

FZ20knowitall
11-30-2004, 11:48 PM
Manxman and I have been doing research about polarizers for the past couple of days, I just dug this up from an old post off of Stevesforums (sorry if some of the info overlaps from the other posts):

"Since this question has appeared so many times here and elsewhere, I'd like to provide an answer once for all. I will try not to be to technical.

A linear polarizer has a single plate for polarizing the incoming light. When this plate, which is attached to the filter, is rotated, the polarized light will change "phase/angle."

Some cameras, especially those SLR/DSLR bodies, have a beam-splitter to split the incoming light to the viewfinder, AF system and metering. Each of these components requires some minimal amount of light to work properly. For example, the AF system usually requires an aperture of F5.6 or larger. Thus, this splitting of light should follow a constant ratio, say 80% to viewfinder, 10% to light meter, and 10% to the AF system (just an example).

If the incoming light is NOT polarized, the phase/angle of the incoming light may be in all directions and evenly distributed to each of the three components. If the incoming light is polarized, depending on the way the incoming light is polarized, the phase/angle of the polarized light may be biased. In other word, since some portion of the incoming light is missing due to polarization, the light diverted to the three components may not be constant. For example, 70% to viewfinder, 5% to light meter, and 8% to the AF system. If the light is polarized significantly, the portion of the incoming polarized light that can reach the AF system may be too low to allow the AF system work properly. Or, if the light that reaches the light meter is lower than the expect level, the meter will "think" the scene illumination is insufficient and force the camera to use a larger aperture and/or a slower shutter speed. As a result, you might get over- or under- exposed images.

To overcome this problem, a second plate is added to a polarizer to "repolarize" the polarized light. The polarizers that have one plate are the "linear" ones, and the polarizers that have two plates are "circular" ones.

Therefore, if your camera does not have a beam splitter, you can use linear polarizers. Virtually all consumer level digicams do not beam splitter, and all SLR/DSLR bodies have beam splitters.
Hope this answers the question well."

The FZ20 does not, I repeat does not have a beam splitter. YOU CAN USE LINEAR POLARIZERS, in fact they usually are cheaper. The only benefit to using a circular polarizer is if you ever want to take it off and use it on an SLR (35mm camera) or DSLR (digital professional camera). But if you just are concerned with your FZ series camera then you can use either polarizer. The linear polarizers are probably a little bit better quality b/c you are shooting thru less glass, therefore, less chance of abberation. But, realistically, nobody would be able to tell the difference between two good quality polarizers (circular or linear).

mikejs304
12-01-2004, 04:42 AM
If you use a linear polarizer and change the position of the camera from portarit to landscape (roate the camera 90 degress) does that affect the polarizing ability of the linear polarizer? When I do that with my circular polarizer I need to rotate the polarizer to get the best results.

genece
12-01-2004, 05:32 AM
Same thing..they work the same way. I matters which way the sun is positioned which is why you must adjust.

manxman
12-01-2004, 11:17 AM
FZ20 :cool: Knowitall,

That was an awesome article that I never ran across. It is amazing to me how there can be such differing experiences about the same thing, but then it just reflects life.

This is a great article of explanation-actually the best I've read. Thanks you for your in depth research and unending curiosity that leads you to share this level of information with all of us.

FZ20knowitall
12-02-2004, 05:38 AM
When I first started studying photography it seemed overwhelming. Even trying to read books take seminars, etc. I still couldn't get a foothold on the thing. It was only when I came across the right person, who could just explain it, not beat around the bush, not assume that I knew stuff that they knew just b/c they knew it. And like anything else, once you know the basics and have a good foundation, then and only then can you build a solid sturdy building. And I am the first to admit it on this forum, I am no expert on a lot of these topics. Photography, yes. The FZ20, yes mainly b/c I read the manual and have a lot of experience w/electronics (and professional video equipment). But because my foundation is solid, I can just do a search find out info and explain it. Plus this forum has helped me to go out and perform tests and do research etc. So...as they say the teacher becomes the student! I think the important thing is that we are all here to learn. Those more advanced or knowledgeable lend their knowledge to the "newbies" and the "newbies" a lot of times turn around and ask some amazing questions that make all of us scratch are noggins and go, "HUH, never quite thought of it that way".

So, let's all keep shooting, questioning and posting and we shall all become better photographers. Maybe we should get together and have a X-mas party, and give out awards n-stuff.........

Jim Last
12-02-2004, 05:48 AM
..... and the award for 'Best Newcomer 2004' goes to ...........{drum roll}......... FZ20knowitall :D

You could have a golden D-Slr statue :D

Cool!

FZ20knowitall
12-02-2004, 10:53 PM
****accepts award humbly, bows, walks off stage*******

Anex
12-03-2004, 01:24 PM
...then rubs butt becuase of the kick he received when bowing...

:p

Jim Last
12-03-2004, 01:54 PM
..... presenter clears throat ............

"Ladies and Gentlemen........FZ20knowitall has left the building"

indawoods
12-14-2004, 05:30 AM
I really appreciate the detailed info on lenses and adaptors. I just got an FZ20 and am learning so much so quickly from this forum.

Jim Last
12-14-2004, 09:53 AM
Glad that you are finding this forum beneficial :) Any queries just post!