qleak
No longer a newbie, moving up!
- Joined
- Dec 11, 2013
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- 629
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- 183
- Location
- Ohio
- Can others edit my Photos
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I'm planning on making a variable density filter by reverse coupling to circular polarizers together. Long story short: I purchased a nice 72mm B&W circular polarizer and got another cheaper Tiffen polarizer for free when I got my newest lens.
I'm currently waiting for the 72-72mm reverse coupler to ship from china.
So why mount in reverse you ask? Well... a circular polarizer is really a linear polarizer with a depolarizer behind it to make the light go in circles again (for your AF's beam splitter). Two linear polarizers will make a variable ND filter when stacked. However, a depolarizer between them negates the effect.
How would you meter the number of stops reduction at maximum?
I'm fairly sure at minimum it is 1.5 stops ( the 2nd filter has a negligible affect).
Best,
-Q
I'm currently waiting for the 72-72mm reverse coupler to ship from china.
So why mount in reverse you ask? Well... a circular polarizer is really a linear polarizer with a depolarizer behind it to make the light go in circles again (for your AF's beam splitter). Two linear polarizers will make a variable ND filter when stacked. However, a depolarizer between them negates the effect.
How would you meter the number of stops reduction at maximum?
I'm fairly sure at minimum it is 1.5 stops ( the 2nd filter has a negligible affect).
Best,
-Q