linear vs circular pol filter
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pookie_old
Veteran
Re: linear vs circular pol filter
Circular, no choice.
Circular, no choice.
XCheck
Veteran
Re: linear vs circular pol filter
But why?
In the SLR world, the usual argument is 'because it messes up autofocus' - which is understandable. Now - I don't use autofocus with DVX - what other camera function would be impacted by the choice of linear vs. circular? Certainly no WB (polarized light doesn't change its wavelength, although the filter may suppress some frequencies more than others). The beam splitter? Possible, but I am not sure.
BTW, I never understood the 'circular' pola filter. In my world, 'circular polarization' is an oxymoron. Either you have polarized light or you don't. Polarized can be elliptical (partially polarized) or linear (completely polarized). This reflects the distribution of the electromagnetic wave orientation as it progresses through space.
Sales reps in photo/video stores don't understand physics, and I can't engage with them in an intelligent debate to explain this to me - all they do is parrot what they read in the product literature.
If anyone understand the difference between circular and linear pola filters and can explain it using PHYSICS, please, please, do so here.
J.
But why?
In the SLR world, the usual argument is 'because it messes up autofocus' - which is understandable. Now - I don't use autofocus with DVX - what other camera function would be impacted by the choice of linear vs. circular? Certainly no WB (polarized light doesn't change its wavelength, although the filter may suppress some frequencies more than others). The beam splitter? Possible, but I am not sure.
BTW, I never understood the 'circular' pola filter. In my world, 'circular polarization' is an oxymoron. Either you have polarized light or you don't. Polarized can be elliptical (partially polarized) or linear (completely polarized). This reflects the distribution of the electromagnetic wave orientation as it progresses through space.
Sales reps in photo/video stores don't understand physics, and I can't engage with them in an intelligent debate to explain this to me - all they do is parrot what they read in the product literature.
If anyone understand the difference between circular and linear pola filters and can explain it using PHYSICS, please, please, do so here.
J.
XCheck
Veteran
Re: linear vs circular pol filter
Sometimes it's better when people don't put cart before the horse (or is it a mule?).
Now - you'll forgive me that I get frustrated with the sales reps. By the time I get home from the store, everything's forgotten and this is no longer a pressing problem, so I never had the incentive to find out - until now.
I just fired the previous post impulsively - for the reason explained above, I cringe every time someone says 'use circular' without explanation WHY.
So - after my post, I took to the internet to dig out some information. Here is a link that explains circular polarization of light: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.html#c3. I can understand THAT. Now, if someone also tells me why it makes a difference in DVX, I'd be happy...
J.
Sometimes it's better when people don't put cart before the horse (or is it a mule?).
Now - you'll forgive me that I get frustrated with the sales reps. By the time I get home from the store, everything's forgotten and this is no longer a pressing problem, so I never had the incentive to find out - until now.
I just fired the previous post impulsively - for the reason explained above, I cringe every time someone says 'use circular' without explanation WHY.
So - after my post, I took to the internet to dig out some information. Here is a link that explains circular polarization of light: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.html#c3. I can understand THAT. Now, if someone also tells me why it makes a difference in DVX, I'd be happy...
J.
Re: linear vs circular pol filter
The answer is simple: there is no difference in video cam applications! A couple of things however: good polarizers have multilayer, scratchfree coatings (a must for all filters) and they are difficult to find in the "cheap" linear polar range. Further on, but very subtile: backreflected rays don't reach the frontface of a circ polar (reduced glare) , and finally there used to exist (but solved now) a design challenge for getting polarisation independant optical crossover properties (color shift) in the dichroic prisms used for 3CCD cams.
The answer is simple: there is no difference in video cam applications! A couple of things however: good polarizers have multilayer, scratchfree coatings (a must for all filters) and they are difficult to find in the "cheap" linear polar range. Further on, but very subtile: backreflected rays don't reach the frontface of a circ polar (reduced glare) , and finally there used to exist (but solved now) a design challenge for getting polarisation independant optical crossover properties (color shift) in the dichroic prisms used for 3CCD cams.
pookie_old
Veteran
Re: linear vs circular pol filter
So buy a linear then, whats the problem?
It's only your money to waste.
So buy a linear then, whats the problem?
It's only your money to waste.
Re: linear vs circular pol filter
either will work fine. but a circular will work for anything you ever want to use it for . theres a 1 in 100,000 chance that a linear pol will cause some issues with a video cam. but i doubt its going toi happen, and if it does you could just return it and get the circular. anyway if you going to buy one just get the circular and save yourself the hassle of ever not having the right kind of polarizer.
and the difference with a circular poalrizer is that it has a layer on the back which effectivly de-polarizes the light using a wave retarder. that way the light wont have a chance to mess with the following optics. so it polarizes the light and is discriminatory as to what gets through but then depolarizes it on the other side again so that its the same polarized image but not polarized light anymore. ... basically. hope that makes sense. im not very good at stating things clearly and concisely because my brain is proccesing things happening next week when im trying to say whats going on now.. and usually i ramble on for a while until my wife tells me that i have two ears and one mouth for a reason.
either will work fine. but a circular will work for anything you ever want to use it for . theres a 1 in 100,000 chance that a linear pol will cause some issues with a video cam. but i doubt its going toi happen, and if it does you could just return it and get the circular. anyway if you going to buy one just get the circular and save yourself the hassle of ever not having the right kind of polarizer.
and the difference with a circular poalrizer is that it has a layer on the back which effectivly de-polarizes the light using a wave retarder. that way the light wont have a chance to mess with the following optics. so it polarizes the light and is discriminatory as to what gets through but then depolarizes it on the other side again so that its the same polarized image but not polarized light anymore. ... basically. hope that makes sense. im not very good at stating things clearly and concisely because my brain is proccesing things happening next week when im trying to say whats going on now.. and usually i ramble on for a while until my wife tells me that i have two ears and one mouth for a reason.