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Two Polarizers VND
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Jul 26, 2018 14:00:19   #
rcarol
 
Have any of you tried to use two stacked polarizers as a VND filter in a pinch? What were your results?

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Jul 26, 2018 14:05:51   #
User ID
 
`

"In a pinch" ?

You mean you anticipate emergencies
requiring that you destroy up to 10EV
worth of light from the scene ?

Stack two CPLs. It might get amusing.
Report back with observations !

`

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Jul 26, 2018 14:22:31   #
Toby
 
User ID wrote:
`

"In a pinch" ?

You mean you anticipate emergencies
requiring that you destroy 10EV worth
of light ?

Stack two CPLs. It might get amusing.
Report back with observations !

`


Amazing that you would rather belittle someone who asks an honest question rather than present information or just be quite. No wonder the world is such a mess.

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Jul 26, 2018 14:27:25   #
Longshadow Loc: Audubon, PA, United States
 
Toby wrote:
Amazing that you would rather belittle someone who asks an honest question rather than present information or just be quite. No wonder the world is such a mess.



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Jul 26, 2018 14:33:30   #
DWU2 Loc: Phoenix Arizona area
 
rcarol wrote:
Have any of you tried to use two stacked polarizers as a VND filter in a pinch? What were your results?


It's been tried before: https://blog.mingthein.com/2014/04/30/experimenting-with-stacked-polarisers/

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Jul 26, 2018 14:36:43   #
rcarol
 
User ID wrote:
`

"In a pinch" ?

You mean you anticipate emergencies
requiring that you destroy up to 10EV
worth of light from the scene ?

Stack two CPLs. It might get amusing.
Report back with observations !

`


I didn't necessarily restrict myself to CPLs.

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Jul 26, 2018 14:42:07   #
rmalarz Loc: Tempe, Arizona
 
rcarol, I've not, but the reason for not is a sound one. I discussed this with an optical engineer at B+W. During the conversation I was informed of the notorious X that can appear at certain combinations of "density" and aperture. I researched this further and decided not to risk ruining photographs with what seemed to be a good solution to using CPs to accomplish what ND filters do. All you have to do is a search in Google Images and enter

x variable neutral density filter

You'll see examples.

This is not to say it won't work all the time, it's just the some of the time that persuaded me to purchase a variety of ND filters.
--Bob
rcarol wrote:
Have any of you tried to use two stacked polarizers as a VND filter in a pinch? What were your results?

Reply
 
 
Jul 26, 2018 14:46:09   #
rgrenaderphoto Loc: Hollywood, CA
 
User ID wrote:
`

"In a pinch" ?

You mean you anticipate emergencies
requiring that you destroy up to 10EV
worth of light from the scene ?

Stack two CPLs. It might get amusing.
Report back with observations !

`


I think the mistake is thinking that adjusting 2 CPLs will knock back light reaching the sensor like a ND. Which won't work, since the function of a CPL is to bend light, and the function of a ND is to reduce the amount of light hitting the sensor, not bend it about.

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Jul 26, 2018 14:54:29   #
Longshadow Loc: Audubon, PA, United States
 
I would imagine you would get different results depending on the initial angle of the first polarizer when rotating the second. You probably would also have different results if you kept the angle between the two filters the same and rotated both filters at the same time. But that's just a guess.

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Jul 26, 2018 15:02:00   #
rcarol
 
rgrenaderphoto wrote:
I think the mistake is thinking that adjusting 2 CPLs will knock back light reaching the sensor like a ND. Which won't work, since the function of a CPL is to bend light, and the function of a ND is to reduce the amount of light hitting the sensor, not bend it about.


I'm not restricting myself to CPLs. What about LPLs?

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Jul 26, 2018 15:14:02   #
Longshadow Loc: Audubon, PA, United States
 
rcarol wrote:
I'm not restricting myself to CPLs. What about LPLs?

Same basic effect.

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Jul 26, 2018 16:23:58   #
rook2c4 Loc: Philadelphia, PA USA
 
Rarely do I carry more than one CPL filter on me. However, in a situation where I had two CPL filters with me but no ND filter, I certainly would not hesitate to try the CPL filters together as a substitute for the ND filter. The way I see it, better to compromise a little than to simply give up and forgo the shot altogether.

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Jul 26, 2018 17:53:23   #
rcarol
 
Longshadow wrote:
Same basic effect.


After posting my original question I decided to do some independent research. Perhaps I should have done this research before posting but I didn't. I found the following article to be of interest:

https://www.instructables.com/id/Simple-Variable-Neutral-Density-Filter/

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Jul 26, 2018 18:01:15   #
Longshadow Loc: Audubon, PA, United States
 
rcarol wrote:
After posting my original question I decided to do some independent research. Perhaps I should have done this research before posting but I didn't. I found the following article to be of interest:

https://www.instructables.com/id/Simple-Variable-Neutral-Density-Filter/


I think I'll stick with my set of three ND filters...

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Jul 26, 2018 18:03:20   #
rcarol
 
Longshadow wrote:
I think I'll stick with my set of three ND filters...


Probably a good idea......

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