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Circular Polarizers, A Filter You Need



 
 
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  #11  
Old August 8th 07, 07:05 PM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Fat Sam[_2_]
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Posts: 9
Default Circular Polarizers, A Filter You Need

Bob Salomon wrote:
In article ,
"Fat Sam" wrote:

But I've used both the linear and the circular polarisers on my
digital and I honestly can't see any difference in the results when
I compare the two.


Nor should there be if they are the same quality. But under some
lighting conditions a linear polarizer will not let the AF or the AE
or both work properly if your camera has a beam splitter in the
optical system. If you have a camera without a beam splitter then you
have no reason to use a circular polarizer.


How would I find out if a camera has a bean splitter?
Serious question with a genuine reason for asking, as I'm planning to
upgrade to a DSLR from my Fuji S5600 as soon as I have the pennies gathered
up.


  #12  
Old August 8th 07, 07:31 PM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Bob Salomon
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Posts: 175
Default Circular Polarizers, A Filter You Need

In article ,
"Fat Sam" wrote:

How would I find out if a camera has a bean splitter?
Serious question with a genuine reason for asking, as I'm planning to
upgrade to a DSLR from my Fuji S5600 as soon as I have the pennies gathered
up.


The simplest way is to just ask tech support for the camera manufacturer
if the camera requires a circular polarizer. Or look at the
manufacturer's accessory catalog and see if they sell a linear or a
circular for it.

The last resort is that a circular polarizer works with all cameras that
it can attach to, analog or digital or video, and will work properly
under all lighting conditions.

If in doubt, and you want to make sure just buy the circular one. But
get a good one that is properly multi-coated on both sides.

--
To reply no_ HPMarketing Corp.
  #13  
Old August 8th 07, 09:06 PM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Tony Polson
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Posts: 1,194
Default Circular Polarizers, A Filter You Need

"Matt Clara" wrote:

"Fat Sam" wrote in message
...
Wayne J. Cosshall wrote:
Hi All,

I've written the first of a series of articles on the use of real
camera filters with digital photography. The first is on the circular
polarizer filter:
http://www.dimagemaker.com/article.php?articleID=1063

Cheers,

Wayne


I have a circular and a linear polariser. I was told that I would be
better to use the circular polariser on my digital camera, as it would
give better results.
But I've used both the linear and the circular polarisers on my digital
and I honestly can't see any difference in the results when I compare the
two.


The circular will tend to give slightly _poorer_ results, as it's designed
to let some polarized light through, as some camera's autofocus systems (and
ttl metering) depends upon it to get the job done.



Not so, Matt.

The circular polariser has two elements. The first is a linear
polariser, which has exactly the same blocking effect as any linear
polariser. The second element is a "quarter wave retarder" which
effectively unpolarises the polarised light, making it acceptable to
autofocus systems and some light metering systems, for example that of
the Nikon F3.

From the B+W web site:
"B+W pol-filters are made in various types and dimensions, both in the
form of linear as well as circular pol-filters. Basically, both
consist of a linearly polarizing film. With a circular polarizing
filter, an additional retardation film is added, which places the
linearly polarized light into rotation, thereby preventing erroneous
measurements in optical measurement systems; hence, for cameras with
internal devices for light meters (TTL) and/or autofocus, only
circular polarizing filters can be used! The same applies to digital
cameras and camcorders."

B+W are being cautious here, because only a very few manual focus SLRs
ever needed a circular polarising filter. Most TTL meters are
perfectly accurate when linear polarisers are used.



  #14  
Old August 8th 07, 09:17 PM posted to rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Joseph Miller
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Posts: 75
Default Circular Polarizers, A Filter You Need- not so- linear vs. circular

Matt Clara wrote:




The circular will tend to give slightly _poorer_ results, as it's designed
to let some polarized light through, as some camera's autofocus systems (and
ttl metering) depends upon it to get the job done.

--
www.mattclara.com



Both the circular and linear devices do exactly the same thing at the
first step- the light goes through a linear polaroid. That is where all
the action happens, all the filtering of the scene. For the simple
linear device, the light exits the filter essentially fully linearly
polarized and then enters the camera. Since reflections off surfaces can
polarize light, if there are any reflections inside the camera- say to
the viewfinder or to the light meter- there is the potential for
interactions, crossings, of this polarization with the incoming
polarization, which could affect the results in a negative way. If there
are no reflections in the camera, if the light goes straight through to
the focal plane and never is reflected, then linear polarized light
inside the camera should be irrelvant.

The circular device simply takes the linearly polarized light from the
first filter and converts it to circularly-polarized light by passing it
through a second filter, a quarter-wave retarder. If the filter is well
made, this second filter should result in no significant loss of light
or any other degradation of image quality. After exiting the filter,
circularly polarized light will pass though a camera just the same as
unpolarized light, in other words, just fine. The critical thing is that
it won't make any difference at what angle you set that first linear
polaroid.

There should be absolutely no difference in image quality between the
two filters if they are of comparable quality. For straight-through
cameras, there should be no performances differences. For cameras with
internal reflections, however, the circular polarizer will give more
reliable results, as the circularly polarized light it produces will be
immune to polarizing effects of the internal relections.

Since linear polarizers tend to be cheaper than circular ones, if you
have a straight through camera, you can probably save some money by
buying a linear device.

I hope this makes it a little clearer.

Joe
  #15  
Old August 8th 07, 09:29 PM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Wayne J. Cosshall
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Posts: 826
Default Circular Polarizers, A Filter You Need

Both polarizers work the same way, just the circular has a second layer
to depolarize the resulting light. The polarizing part does the same
thing, so there should be no difference, all other things being equal.
However there are different materials used and so they can vary
significantly between brands and even within brands if the manufacturer
has changed process.

Some cameras will be more sensitive to linear polarization than others,
but if you were buying now it is probably not worth the risk and just
get a circular one.

Cheers,

Wayne

Wayne J. Cosshall
Publisher, The Digital ImageMaker, http://www.dimagemaker.com/
Blog http://www.digitalimagemakerworld.com/
Publisher, Experimental Digital Photography
http://www.experimentaldigitalphotography.com
Personal art site http://www.cosshall.com/



Fat Sam wrote:
Wayne J. Cosshall wrote:
Hi All,

I've written the first of a series of articles on the use of real
camera filters with digital photography. The first is on the circular
polarizer filter:
http://www.dimagemaker.com/article.php?articleID=1063

Cheers,

Wayne


I have a circular and a linear polariser. I was told that I would be better
to use the circular polariser on my digital camera, as it would give better
results.
But I've used both the linear and the circular polarisers on my digital and
I honestly can't see any difference in the results when I compare the two.


  #16  
Old August 8th 07, 09:42 PM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Wayne J. Cosshall
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Posts: 826
Default Circular Polarizers, A Filter You Need

They were all exposed using auto exposure and none were autoleveled or
such in PS. Yes the first is over exposed to what I would want but I
left it in because I found it quite interesting that the camera itself
would get such different exposures of the scene with and without the filter.

For the article I used a quite wideangle lens to show the variation in
sky darkening with such a lens. With a narrower lens the sky effect can
be very strong with the right direction of camera relative to sun and
is, IMO, a very useful creative tool.

As to the rest of your comments, grow up. I publish an online magazine,
the same as the print photo mags I used to edit. I have every right to
put advertising on there if I want. If people don't want to they do not
have to click on anything except read the article. As it is I earn about
enough to cover my hosting costs. I assume you expect to get paid from
your job. Providing a site like DIMi, paying the costs and spending the
time organising the competitions, prizes, doing the reviews and
answering people's questions is a major effort. I do not see whiners
like you doing anything like this. Sure you'll get on a list and offer
opinions, it takes no real effort. When you put in the effort to do a
site like DIMi and keep doing it year on year then I might listen to
your crap.

Wayne J. Cosshall
Publisher, The Digital ImageMaker, http://www.dimagemaker.com/
Blog http://www.digitalimagemakerworld.com/
Publisher, Experimental Digital Photography
http://www.experimentaldigitalphotography.com
Personal art site http://www.cosshall.com/



Matt Clara wrote:
On Aug 8, 5:33 am, "Wayne J. Cosshall" wrote:
Hi All,

I've written the first of a series of articles on the use of real camera
filters with digital photography. The first is on the circular polarizer
filter:

Cheers,

Wayne


I have one, rarely use it. Additionally, a 77mm multi-coated circular
polarizer to fit a great majority of my lenses, including my Mamiya
gear, costs a minimum of $150. It's not worth the money. And about
your examples, in the first series of thumbnail images, the one w/out
polarizer is clearly over exposed, the ones in which you indicate
reduced reflection from water and foliage are different, but not
necessarily better, and the darkened sky images look unnatural (and
again, you tend to overexpose, particularly in the ones with the dam
in the background). This is not to say the circular polarizer is not
without its uses, but to say it's a filter one "needs" is a stretch,
and a big one at that.

Finally, aren't you in essence spamming the photography groups in an
attempt to make money off our visits to your website, which are
replete with advertising? If you want to share info here, please do,
but your capitalist endeavors aren't welcome.

--
www.mattclara.com (not a single image there taken with a polarizer)

  #17  
Old August 8th 07, 09:46 PM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Wayne J. Cosshall
external usenet poster
 
Posts: 826
Default Circular Polarizers, A Filter You Need

Actually I should add that the camera manual will often specify whether
a circ. pol. is needed with a particular model. If not, tech support or
the support pages on their web site should be able to tell you.

Cheers,

Wayne

Wayne J. Cosshall
Publisher, The Digital ImageMaker, http://www.dimagemaker.com/
Blog http://www.digitalimagemakerworld.com/
Publisher, Experimental Digital Photography
http://www.experimentaldigitalphotography.com
Personal art site http://www.cosshall.com/



Wayne J. Cosshall wrote:
Both polarizers work the same way, just the circular has a second layer
to depolarize the resulting light. The polarizing part does the same
thing, so there should be no difference, all other things being equal.
However there are different materials used and so they can vary
significantly between brands and even within brands if the manufacturer
has changed process.

Some cameras will be more sensitive to linear polarization than others,
but if you were buying now it is probably not worth the risk and just
get a circular one.

Cheers,

Wayne

Wayne J. Cosshall
Publisher, The Digital ImageMaker, http://www.dimagemaker.com/
Blog http://www.digitalimagemakerworld.com/
Publisher, Experimental Digital Photography
http://www.experimentaldigitalphotography.com
Personal art site http://www.cosshall.com/



Fat Sam wrote:
Wayne J. Cosshall wrote:
Hi All,

I've written the first of a series of articles on the use of real
camera filters with digital photography. The first is on the circular
polarizer filter:
http://www.dimagemaker.com/article.php?articleID=1063

Cheers,

Wayne


I have a circular and a linear polariser. I was told that I would be
better to use the circular polariser on my digital camera, as it would
give better results.
But I've used both the linear and the circular polarisers on my
digital and I honestly can't see any difference in the results when I
compare the two.

  #18  
Old August 8th 07, 10:02 PM posted to rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
acl
external usenet poster
 
Posts: 1,389
Default Circular Polarizers, A Filter You Need- not so- linear vs. circular

On Aug 9, 12:17 am, Joseph Miller wrote:

After exiting the filter,
circularly polarized light will pass though a camera just the same as
unpolarized light, in other words, just fine. The critical thing is that
it won't make any difference at what angle you set that first linear
polaroid.


Just to clarify this a bit, the angle of the polaroid filter makes no
difference as far as the passage through the camera is concerned (ie
it is not the case that, when it is set to some orientation, the AF
system, say, will fail). It does make a difference to the
transmittance, ie it does change the way the scene looks. I imagine
that this is what you meant, but what you wrote is a bit ambiguous.

  #19  
Old August 9th 07, 10:41 PM posted to rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Joe Miller
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Posts: 7
Default Circular Polarizers, A Filter You Need- not so- linear vs. circular

In article . com,
acl wrote:

On Aug 9, 12:17 am, Joseph Miller wrote:

After exiting the filter,
circularly polarized light will pass though a camera just the same as
unpolarized light, in other words, just fine. The critical thing is that
it won't make any difference at what angle you set that first linear
polaroid.


Just to clarify this a bit, the angle of the polaroid filter makes no
difference as far as the passage through the camera is concerned (ie
it is not the case that, when it is set to some orientation, the AF
system, say, will fail). It does make a difference to the
transmittance, ie it does change the way the scene looks. I imagine
that this is what you meant, but what you wrote is a bit ambiguous.


Yes, you put it more clearly. I meant as far as light going through the
camera itself is concerned, it makes no difference at which angle the
leading polaroid is set.

Joe
 




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