How the hell do I get my CPL to work :S

[Stosh]

anyone ever find their blue skies becoming far too dark when the polarizer has been adjusted to provide the darkest sky? Hard to tell in camera, but when viewing on a computer it's obvious, and difficult to get a normal looking sky back...

I noticed this when I traveled to the West. In dry air like SE USA you guys already have cobalt blue skies. When you add the polarizer it almost looks fake - almost outer space like. Here in the east we have humidity and it's rare to have the deep blue skies like you guys have. Here it's almost impossible to have too much polarizing effect.

 

[UUilliam]

what would happen if you put 2 CPL's on?
could you get Darker skies or, get a dark sky + remove reflections?
(not doing it, just curious.)

 

[DennyCrane]

a polarized filter is 2 pieces of glass with minute lines etched into the surfaces. The result is varying degrees of light >>coming in from a particular angle<< being blocked out. Standard (non-circular) polarized glass can completely block out light if placed so the lines are at right angles to each other.

Now comes the weird part...

Put another piece of polarized glass on front of those at a right angle again... and light comes through. I can't explain it, it has something to do with quantum mechanics and I only pretend to be a lawyer, not a scientist.

But a 2nd polarizer would introduce 4 etched pieces of glass in front of the lens and the results would be unpredictable at best.

But, try it and let us know. Seriously.

 

[Garbz]

1 CPL + 1 CPL you would get retarded colour patterns. 1 LPL + 1 CPL or 1 LPL + 1 LPL will give you a variable ND filter from about 2 stops to completely black (well ideally anyway).

The light coming out of the back of a CPL is circularly polarised meaning that any effect caused by polarisation of the sky or ground has been altered. Put another polariser on it and you'll show cool patterns.
Light out of the back of a LPL is linearly polarised. Put another polariser behind it with the same angle and you just lose 1 extra stop of light due to the filter. But rotate that second filter 90deg from the first and you effectively cut off all light.

:Lol: it has nothing to do with quantum mechanics, it's electromagnetics

 

[iolair]

2 Polarisers would reduce heavily the amounts of any light entering the lens - put them at 90 degrees to each other, and you'll see nothing at all.

 

[DennyCrane]

2 yes, 3 no. 4? Hmmm

 

[Plato]

2 Polarisers would reduce heavily the amounts of any light entering the lens - put them at 90 degrees to each other, and you'll see nothing at all.

That's true only if the polarizer furthest from the camera is the old linear style polarizer.

 

[Plato]

1 CPL + 1 CPL you would get retarded colour patterns. 1 LPL + 1 CPL or 1 LPL + 1 LPL will give you a variable ND filter from about 2 stops to completely black (well ideally anyway).

The light coming out of the back of a CPL is circularly polarised meaning that any effect caused by polarisation of the sky or ground has been altered. Put another polariser on it and you'll show cool patterns.
Light out of the back of a LPL is linearly polarised. Put another polariser behind it with the same angle and you just lose 1 extra stop of light due to the filter. But rotate that second filter 90deg from the first and you effectively cut off all light.

:Lol: it has nothing to do with quantum mechanics, it's electromagnetics

Don't forget that LPL+CPL will give different results than CPL+LPL. It's electromagnetic wave theory (which I did study many years ago).

 

[DennyCrane]

1 CPL + 1 CPL you would get retarded colour patterns. 1 LPL + 1 CPL or 1 LPL + 1 LPL will give you a variable ND filter from about 2 stops to completely black (well ideally anyway).

The light coming out of the back of a CPL is circularly polarised meaning that any effect caused by polarisation of the sky or ground has been altered. Put another polariser on it and you'll show cool patterns.
Light out of the back of a LPL is linearly polarised. Put another polariser behind it with the same angle and you just lose 1 extra stop of light due to the filter. But rotate that second filter 90deg from the first and you effectively cut off all light.

:Lol: it has nothing to do with quantum mechanics, it's electromagnetics

The effects of polarized light through three filters has everything to do with quantum mechanics... I was just too lazy to brush up on it since it'd been a long time since I was studying this. And I did make a mistake...

Take 2 polarized pieces of glass, and have the furthest 90° rotated from the first and no light will pass through. Now add a 3rd rotated at 45° and place it between the original 2, and light passes through again. This is part of the Copenhagen interpretation of quantum mechanics. Here's a .pdf if you're interested... it's a little dry, but explains the concept in experiment 3:
http://ocw.mit.edu/NR/rdonlyres/Che...5FBF69-625B-4A65-8CDB-F18C2E386755/0/sec1.pdf

 

[Plato]

1 CPL + 1 CPL you would get retarded colour patterns. 1 LPL + 1 CPL or 1 LPL + 1 LPL will give you a variable ND filter from about 2 stops to completely black (well ideally anyway).

The light coming out of the back of a CPL is circularly polarised meaning that any effect caused by polarisation of the sky or ground has been altered. Put another polariser on it and you'll show cool patterns.
Light out of the back of a LPL is linearly polarised. Put another polariser behind it with the same angle and you just lose 1 extra stop of light due to the filter. But rotate that second filter 90deg from the first and you effectively cut off all light.

:Lol: it has nothing to do with quantum mechanics, it's electromagnetics

The effects of polarized light through three filters has everything to do with quantum mechanics... I was just too lazy to brush up on it since it'd been a long time since I was studying this. And I did make a mistake...

Take 2 polarized pieces of glass, and have the furthest 90° rotated from the first and no light will pass through. Now add a 3rd rotated at 45° and place it between the original 2, and light passes through again. This is part of the Copenhagen interpretation of quantum mechanics. Here's a .pdf if you're interested... it's a little dry, but explains the concept in experiment 3:
http://ocw.mit.edu/NR/rdonlyres/Che...5FBF69-625B-4A65-8CDB-F18C2E386755/0/sec1.pdf

This is all academic in our environment because the entire discussion relates to linear polarizers and obviously we don't use linears with our cameras.

 

[Garbz]

I did say CPL+LPL is different then LPL+CPL. I probably shouldn't have used + though and been clearer.

This really is all academic. One can describe it with quantum mechanics, but why try hit a fly with a hammer is more what I was getting at. Basic electromagnetics talk about the ratios of vectors and components travelling in certain directions. Then the solution of how much light passes through polarisers becomes it's insertion loss + year 10 triginometry

Gotta love physics, everything can be explained in 6 different ways.