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#11
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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
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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
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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
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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
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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
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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
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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
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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
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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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