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Old May 24, 2004, 2:56 PM   #1
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1 what is the difference between linear & circular polarizers?
advantages & disadvantages of each
2 what is the difference between a skylight filter & a uv filter?




THANKS YOU

LOU
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Old May 24, 2004, 3:19 PM   #2
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1. Although I can't explain the technical (optical) difference between a linear polarizer and a circular polarizer, the circular filter costs about twice as much. Most manufacturers of auto-focus camera state that a linear polarizer will cause the auto-focus system to malfunction. The may be true in some cases and false in others. I used a linear polarizer on a Nikon N70 for many years and never had a bit of trouble.

My recommendation is to try a linear polarizer on your camera and see if it works ok. If so, you just saved about $20-30. If the auto-focus malfunctions, dump the linear and get a circular.

Note that manual focus, if available, will work with either type of filter.

2. UV and Skylight filters are essentially the same thing. Neither has much effect on the image. They cut UV haze slightly but not much. A more important use for a UV filter is to protect the front element of your camera lens. Replacing a cracked or scratched filter costs about $20-40. Replacing a lens with a cracked or scratched front element could cost $200-1000 or more. Which would you rather replace? I have UV filters protecting every lens of every camera I own.

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Old May 24, 2004, 5:08 PM   #3
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I'M GETTING THE UV FILTER AND THE LESS EXPENSIVE LINEAR FILTER TO USE WITH

THE ALTERNATE MANUAL FOCUS ON MY PAN FZ10 SINCE IT'S MUCH CHEAPER & P[ROVIDES THE SAME RESULT



RIGHT?

THANKS

LOU LEDDA
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Old May 24, 2004, 8:36 PM   #4
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If you are going to become involved with any sort of polarizing filters you will probably be rapidly disappointed if you don't understand at least a little of the physics behind polarization and what the filters are doing. Since ET has not called in on this one I will attempt to give an orientation.

Light, for most purposes of physical optics, can be thought of as "stuff" traveling in rays, or straight lines. As it travels from point A to point B it actually is composed of two different kinds of "stuff" , the electromagnetic "stuff" and the magnetic "stuff", which vibrate at right angles to the direction of the travel. A rough analogy would be to think of a long string connecting point A to point B and the string is vibrating in two direction at once. With respect to the idea of polarization, things start to get interesting when the light ray is reflected by or absorbed by certain kinds of materials. Glass, metalic surfaces, etc. have the property that they reflect one of the types of "stuff" and not the other. When this happens the reflected light is said to be polarized and the original "stuff" retains its direction of vibration.. Film and the human eye cannot see the difference between the types of "stuff". However, some materials, such as the materials used in linear polarizer filters see the difference and allow only one of the types to pass. The amount of passage depends upon the orientation of the filter. Think of standing before an open venetian blind and trying to stick the fingers of your open hand through the openings. This is possible only when your hand in in a certain position. That is the way polarized light works. So, for instance, if you are walking down the street on a sunny day and see a store window you want to photograph into but there is a strong reflection of polarized skylight blocking the view into the window, you whip out your polarizing filter and see if it blocks the reflected (polarized) light. That is the basic idea behind using linear polarizing filters. Circular polarizers are sort of like reduced strength linear polarizers that cover all directions. Another common use of polarizing filters is in landscape photography since clear sky is polarized depending on the direciton from the sun, A polarizing filter can block the polarized part of the sky and effectively darken it, an effect which works regardless of color considerations since polarization has nothing to do with color itself.

Hope this helps.

Richard S.

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Old May 24, 2004, 10:50 PM   #5
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You only need a circular polarizer if you have a dSLR or modern SLR with a beam splitter or semi-silvered mirror. Other consumer digitals will be fine with a linear polarizer.

I have to add that many camera stores (especially staffed by minimum wage, uneducated "employees") will try to sell you the circular polarizer to first make more profit, and second they know it will work with any digital so they don't have to worry about returns!
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Old May 24, 2004, 11:25 PM   #6
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Mikefellh wrote:
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thanks for the info

only one more thing.

i heard that with a panasonic fz10 the linear will not work with the auto focus only the manual bum scoop or what?

of course i am dying to get the cheaper type if at all possible

lou ledda



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You only need a circular polarizer if you have a dSLR or modern SLR with a beam splitter or semi-silvered mirror. Other consumer digitals will be fine with a linear polarizer.

I have to add that many camera stores (especially staffed by minimum wage, uneducated "employees") will try to sell you the circular polarizer to first make more profit, and second they know it will work with any digital so they don't have to worry about returns!
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Old May 25, 2004, 1:30 AM   #7
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Difference between UV (aka. haze) and skylight - the skylighthas amarginal pinkish tint. This gives a slight warming effect on film (1A is less severe than 1B). With digital, there effect is negated by the auto white balance on your camera - so it serves much the same function as a UV/haze filter, ie. cuts wavelengths beyond the violet part of the spectrum from reaching the sensor.

In theory, a skylight 1B (the stronger of the two available: 1A and 1B) reduces light transmission by 1/10th stop on average. In practise, this light loss should be ignored (since modern cameras meter with only 1/3 stop precision).
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Old May 25, 2004, 8:31 AM   #8
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PAISANO5 wrote:
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[b]¬*only one more thing.

¬*i heard that with a panasonic fz10 the linear will not work with the auto focus only the manual¬*¬*¬*¬*¬* bum scoop or what?

of course i am dying to get the cheaper type if at all possible
The FZ-10 *should* work with a linear...I say should because I don't know if there are any issues with the OIS system Panasonic uses. It's only a few dollars difference between linear and cicular polarizers if you shop around. You should ask in the Panasonic forum here.
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Old May 26, 2004, 3:03 PM   #9
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If tue front element of your lens rotates while focusing or zooming, you need a circular polarizer. If it does not rotate, a linear filter will work.
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Old May 26, 2004, 3:13 PM   #10
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Not true! You just need to readjust the polarizer AFTER focusing.
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