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I spend too much of my life on TPF!
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01-07-2009 10:15 PM
# ADS
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you can also try looking at a glass building with the sun shining and turn it. It's pretty neat. Actually learned in my physics class how they work. But if you want to know how they work just Google it
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I spend too much of my life on TPF!
I will try that. That sounds like it would create an awesome effect! The first time I have actually experienced something like this effect is with my Ray Ban sun glasses. 
-Christopher
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I spend too much of my life on TPF!
sorry my noobyness but how do you adjust or turn on a filter?
-Canon Powershot S5
-Canon EOS Rebel XSi
-18-55mm EF-S f/3.6-5.6 IS
-18-200mm EF-S f/3.5-5.6 IS
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I spend too much of my life on TPF!
Hey! Don't be sorry. Ask any question you want. Ok, most filters like the UV filter is made up of a glass, surrounded by an outer rim that screws onto your lens you are using. The polarizer or at least the digital polarizer that I bought has a rotating portion so when you screw it onto your lens that you are using the front portion twists which adjusts the glare that is on an object. Does this make sense?
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I spend too much of my life on TPF!
kinda, so when its screwed on, you can turn another ring to turn the filter?
-Canon Powershot S5
-Canon EOS Rebel XSi
-18-55mm EF-S f/3.6-5.6 IS
-18-200mm EF-S f/3.5-5.6 IS
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I spend too much of my life on TPF!
Yes! I don't know why I couldn't say it as plainly as you said it. Yes you turn another ring to adjust. Sad thing is it was like $90.00 for the filter. Well I don't know the difference between digital and non. I got the digital because I had the money and new it had to have been better.
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Been spending a lot of time on here!
What you got was a circular polarizer, there are also linear polarizers that do not have the rotating adjustment for angle of polarization.
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I spend too much of my life on TPF!
i didn't realize there was digital and analog polarizers. (j/k)
yeah what you got was a circular polarizer which can be adjusted as to the intensity of the effect. You can be polarizers which are just the same as say a UV filter but they are not adjustable and have a set intensity for the polarizing effect.
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Umm linear polarizers rotate too...... ALL polarizing filters rotate. There is no "set ammount of polarization" because th eammount of polarization has factors including the light source direction, the glare angle, and so fourth. The "circular" refers to tiny rows of little circles to allow diamond shaped wedges of light through at polarizes arrays as apposed to lines of...well..........lines that only lets little strips of light through. The reason circular polarizers are used is because the camera looks in between the circles to autofocus based on contrast as apposed to being thrown off by lines of high contrast on a linear polarizer, and hunting for focus even in broad daylight.
an example od a circular polarizer layout:
000000000000000000000000000000
000000000000000000000000000000
000000000000000000000000000000
plarizing direction in this position (filter would be able to rotate): <----->
now a linear layout:
||||||||||||||||||||||||
||||||||||||||||||||||||
||||||||||||||||||||||||
polarizing direction in this example(also can rotate):
^
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v
The digital vs film filters are a myth to make you spend more money by the way. Almost all polarizers are circular now, since the AF system hasbeen out for quite some time.
Y eah, I wish I used mine more, only problem is, one of my lenses rotates when focusing (EF 28-70 1:3.4-4.5 Mk I), and the other (EF 50 1:1.8Mk I)has a lens hood superglued onto it by the old owner, so reaching in to rotate the filter is impractical. When I get my EF 70-200 1:4 L in a few days, I am going to buy a 67mm polarizer so I can go back to reducing glare in automotive pictures like I used to with my EF 50 1:1.8 Mk II that didn't have a hood glued on it.
Last edited by DSLR noob; 01-08-2009 at 02:18 AM.
KEEP THIS IN MIND IF I CRITIQUE YOUR PHOTO
This was an open minded opinion and I tried to make it more meaningful than just tearing the photo apart. I simply highlight what I find to be a strength or a weakness that enhances or degrades the quality of an image. I want it to be clear that I respect your right to agree or disagree with my viewpoints, but hope that they may have given you some insight or further understanding when you compared and contrasted my views with your own.
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I spend too much of my life on TPF!
See... that is my problem. Both of my lenses rotate when adjusting the polarizer so this then causes it to go out of focus.
hmmmm so I spent more money than I should have huh? Oh well. What's done is done!
I'm not taking it back. I wandered why something would be called digital if there is nothing digital about it. I thought maybe it was made perfect for digital cameras for some reason or another.
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I spend too much of my life on TPF!
A word about polarization, as there seems to be some confusion.
Light travels in a straight line, but light also has properties which are transverse to the direction it propagates. Specifically, the electric field oscillates transversely to the direction of propagation. so if you are looking down the direction that the light goes it can have two different polarizations, say vertical and horizontal:
Vertical
|
| ------- Horizontal
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And most light is composed of roughly equal parts of these types of polarization. Now, when light reflects at a particular angle, (Brewster's angle if you care), it will reflect only one polarization. But any other reflections will unequally reflect different polarizations. A polarizing filter will block only one type of light, depending on how its polarized. So by rotating a polarizer, you can block different amounts of polarized light. Most notably, surface of water, and other things like cars, and the sky, when viewed at 90 degrees to the sun is highly polarized.
A circular polarizer is in fact a linear polarizer, followed by a quarter wave plate which turns the linear polarized light into circular polarized light (which is just a combination of the two linear polarized directions).
The reason for this is that the beam splitter that is used to focus part of the light to an auto focus, and part into the viewfinder, uses reflections and transmissions which are polarization dependent. so if the light entering the camera, from the filter, is polarized, it may or may not actually make it to the autofocus. So the waveplate rotates the light so that it sends equal amounts of light to the autofocus, but it still has exactly the same effect as a linear polarizer.
I don't know what a digital polarizer is.
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I spend too much of my life on TPF!

Originally Posted by
Eldrich
A word about polarization, as there seems to be some confusion.
Light travels in a straight line, but light also has properties which are transverse to the direction it propagates. Specifically, the electric field oscillates transversely to the direction of propagation. so if you are looking down the direction that the light goes it can have two different polarizations, say vertical and horizontal:
Vertical
|
| ------- Horizontal
|
And most light is composed of roughly equal parts of these types of polarization. Now, when light reflects at a particular angle, (Brewster's angle if you care), it will reflect only one polarization. But any other reflections will unequally reflect different polarizations. A polarizing filter will block only one type of light, depending on how its polarized. So by rotating a polarizer, you can block different amounts of polarized light. Most notably, surface of water, and other things like cars, and the sky, when viewed at 90 degrees to the sun is highly polarized.
A circular polarizer is in fact a linear polarizer, followed by a quarter wave plate which turns the linear polarized light into circular polarized light (which is just a combination of the two linear polarized directions).
The reason for this is that the beam splitter that is used to focus part of the light to an auto focus, and part into the viewfinder, uses reflections and transmissions which are polarization dependent. so if the light entering the camera, from the filter, is polarized, it may or may not actually make it to the autofocus. So the waveplate rotates the light so that it sends equal amounts of light to the autofocus, but it still has exactly the same effect as a linear polarizer.
I don't know what a digital polarizer is.
But however, when I A-B an old, linear polarizer and a circular polarizer, the old linear polarizer has a markedly more dramatic effect (of course, I have to manually focus with the linear filter- anyone remember manual focus, lol?). And is it just me, or are "modern" focusing screens a step backwards? Thinking of ordering one of these...
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I spend too much of my life on TPF!
so...with all that said. What's a good polarizer to get for a Canon Rebel XS that won't make me change my focus as well?
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Keeper of the Padlocks
Site Moderator
Polarizers are defintaly good for macro work - there is even a method where you put polarizer on the flash as well as on the lens and combine the effects of both on the light.
As for focusing screens, modern digi cams are made for working with AF and not manual focusing. I do agree the screens are very tricky to use (especially if the lighting is not fantastic).
As for a circular polarizer a Hoya or B & W make circular polarizer would be agood investment. Get the best you can afford and don't aim for the lower end of the market - no sense putting cheap glass on the end of a lens