Thread: Any difference if the variable nd is behind the lens or in front of the lens?

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  1. #1 Any difference if the variable nd is behind the lens or in front of the lens? 
    I bought the polar pro base camp matte box and it has the variable nds, any benefit or difference if i where to get the kipper tie revolva nd mount? Is it worth it when you have the variable nd matte box in front of the lens?
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  2. #2  
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    Would love to know this myself
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    Senior Member John Marchant's Avatar
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    Variable NDs come with a lot of image quality compromises due to the way they work. Crossing over two polarising filters to darken the image leads to colour shift, changes to reflections and light in general.

    Filtration behind the lens tends to be less susceptible to internal reflections and ghost images.

    Very significant to note: Revolva is not a vari ND, it is a rotating cartridge system containing multiple real glass NDs of cinema grade.
    KipperTie - Authorised RED Rental, Pinewood Studios, UK
    Ready to hire: Monstro 8K VV | Gemini 5K | Helium Monochrome 8K
    Check out our Revolva ND solution, OLPFs and other products
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    Senior Member Patrick Tresch's Avatar
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    Hello John,

    How do you see the difference between filtering with ND in front of the lens VS behind the lens?
    Do optical design of the lens (telecentric or not) have a significant influence to the quality of the picture when there is a filter behind the lens?
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    Senior Member Jacek Zakowicz's Avatar
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    There is a major difference in using front and rear filters. Rear filters affect the back focus and their flatness is crucial for wide angle lenses. These two reasons make them not very well suited for wide angle lenses. For wide angle to normal lenses, generally speaking, front filtering is preferred. Front filters do not affect the back focus but their flatness is critical for lenses starting at 120mm-150mm and up. The long lenses, due to the ray geometry, are not as sensitive to back focus and rear filter flatness. There fore rear filters are preferred for telephoto lenses. The generous amount of space behind the rear glass in telephoto lenses also helps with the mechanical design of placing the rear filter holders in the lens barrel- unlike the wide angle lens design.
    so in short- wide to normal,/short tele lenses- front filters. Telephoto lenses- rear filters.
    hope that helps...
    Jacek Zakowicz, Optitek-dot-org, jacek2@optitek.org
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    From my experience having ND's behind the lens produces much much cleaner images all around. It's the only way to go IMO.
    Daniel Kelly Brown
    www.danielkellybrown.com

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    Senior Member Patrick Tresch's Avatar
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    Quote Originally Posted by Jacek Zakowicz View Post
    There is a major difference in using front and rear filters. Rear filters affect the back focus and their flatness is crucial for wide angle lenses. These two reasons make them not very well suited for wide angle lenses. For wide angle to normal lenses, generally speaking, front filtering is preferred. Front filters do not affect the back focus but their flatness is critical for lenses starting at 120mm-150mm and up. The long lenses, due to the ray geometry, are not as sensitive to back focus and rear filter flatness. There fore rear filters are preferred for telephoto lenses. The generous amount of space behind the rear glass in telephoto lenses also helps with the mechanical design of placing the rear filter holders in the lens barrel- unlike the wide angle lens design.
    so in short- wide to normal,/short tele lenses- front filters. Telephoto lenses- rear filters.
    hope that helps...
    Thanks a lot for your time Jacek. Love to learn more about lenses.

    Quote Originally Posted by Daniel Kelly Brown View Post
    From my experience having ND's behind the lens produces much much cleaner images all around. It's the only way to go IMO.
    Cleaner than in front of the lens? Is it due to some additional flairing?
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