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Thread: Create Fader ND out of 2 CPL Filters

  1. #1

    Default Create Fader ND out of 2 CPL Filters

    This is nothing new but I have tried it myself and it works. Using a flip over glass of one circular polarizer filter (CPL) stack/screw over another CPL filter, you have a variable or fader ND filter.

    At near maximum fade out, you will experience hue change depending on the filter brand, so you have to try it and figure out how to compensate the RGB yourself.

    Here is the quick video I have recorded. (if it gets jerky, just replay after buffer)
    http://spheredomephotoblog.com/attachments/2CPLtoND.avi

    I removed the glass secure ring (extreme caution and patience required), reverse the glass and put it back into place. * Note that the once reverse, the filter looses it's polarizing ability.

    The stacking orientation must be lens, CPL then reverse glass CPL filter. See below:

    - by turn either one of the CPL (not both) will increase darkening intensity.





    - If you put the reverse glass CPL (top) first, then the normal CPL (bottom), you get a change in color instead.

    Last edited by spheredome; 1st August 2009 at 10:29 PM.

  2. #2

    Default Re: Create Fader ND out of 2 CPL Filters

    "I removed the glass secure ring (extreme caution and patience required), reverse the glass and put it back into place. * Note that the once reverse, the filter looses it's polarizing ability."

    Huh?! That's pretty dumb, just stack a Linear Polarizer on top on a Circular Polarizer, don't screw tight and rotate the Linear Polarizer. Only thing to note - rotate the whole Linear Polarizer, not the ring.

  3. #3
    Senior Member limwhow's Avatar
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    Default Re: Create Fader ND out of 2 CPL Filters

    Quote Originally Posted by chrisyeong View Post
    "I removed the glass secure ring (extreme caution and patience required), reverse the glass and put it back into place. * Note that the once reverse, the filter looses it's polarizing ability."

    Huh?! That's pretty dumb, just stack a Linear Polarizer on top on a Circular Polarizer, don't screw tight and rotate the Linear Polarizer. Only thing to note - rotate the whole Linear Polarizer, not the ring.
    Dear Sir,
    You may have a great idea.
    But when you decide to talk down in such a manner to another fellow human, I am afraid you may have inadvertently lost all positive attention that your idea may have generated, and together with it, whatever respect you may have garnered.
    I wish you the very best in all your future endeavour.

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    Senior Member shierwin's Avatar
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    Default Re: Create Fader ND out of 2 CPL Filters

    Another way of using 2 CPL flters as variable ND filter is to use a male-male adapter to allow the 2nd CPL to reverse mount on to the 1st CPL. That will keep the CPL function of the 2nd filter intact. Unfortunately, as far as I know, locally, the male-male adapter ring range is rather limited, mainly 52-52, 52-58 and 58-58 from tagotech. You may find them elsewhere.

    Somehow both "off the market" and "home made" variable ND filters are rather thick and can cause vignetting.

  5. #5

    Default Re: Create Fader ND out of 2 CPL Filters

    Regardless of CPL type, it is important to know that the right glass combo will give the least discoloration near the max, thus those branded vari ND does have their value reason. For this one I was trying, once it reaches 60%, the hue is out, so not really usable (purple color).

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    Moderator ed9119's Avatar
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    Default Re: Create Fader ND out of 2 CPL Filters

    chrisyeong , we are here to share ........... you have rebutted TS.... we respect that.... but pls do not use rude comments
    shaddap and just shoot .... up close
    Walkeast

  7. #7

    Default Re: Create Fader ND out of 2 CPL Filters

    Quote Originally Posted by spheredome View Post
    Regardless of CPL type, it is important to know that the right glass combo will give the least discoloration near the max, thus those branded vari ND does have their value reason. For this one I was trying, once it reaches 60%, the hue is out, so not really usable (purple color).
    will it work best with the best CPLs out there? Say dual B+W KSM CPLs? If this work it sure beats having to bring all my NDs out to the field.
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    Default Re: Create Fader ND out of 2 CPL Filters

    Quote Originally Posted by spheredome View Post
    Regardless of CPL type, it is important to know that the right glass combo will give the least discoloration near the max, thus those branded vari ND does have their value reason. For this one I was trying, once it reaches 60%, the hue is out, so not really usable (purple color).
    Hmmm, can you clarify on what you mean by 60%? Around how many stops?

    Even the "branded" variable ND filters have issues like a crossbar effect, or a slight colour cast when you approach very high stops (8 or so) especially on UWAs. I'll much rather slap on my 10 stop ND if I wanted such a long exposure.

  9. #9
    Senior Member giantcanopy's Avatar
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    Default Re: Create Fader ND out of 2 CPL Filters

    Quote Originally Posted by spheredome View Post
    Regardless of CPL type, it is important to know that the right glass combo will give the least discoloration near the max, thus those branded vari ND does have their value reason. For this one I was trying, once it reaches 60%, the hue is out, so not really usable (purple color).
    My slim Vari-ND works well even past the recommended 8 stops, no funkiness or cast noted. But i think (Singh Ray) themselves do not vouch for funny things that happens in that zone.

    spheredome what do u mean by 60% ?

    Alternatively u need 2 very high quality thin polarisers to DIY something like that.

    ryan

  10. #10

    Default Re: Create Fader ND out of 2 CPL Filters

    I don't know how many stop is that but what I meant was when the glass are around 60% dark, the hue change began to loss control. If you look at the avi file, the inital stage will be ok, hue behaves like any darken glass, then as it darken further, you will see a color change.

    According to some websites, all Hoya combo does pretty well and I tried it too with improved usable ND but you still can't shot at max ND bec of hue.

    If you are keen in building one for fun, chris did mention getting a linear PL, which will be your first choice (but I am not sure it linear will impair the focusing, hard to get linear PL now a days).

  11. #11

    Default Re: Create Fader ND out of 2 CPL Filters

    If anyone happens to have 2x high quality "thin" CPL pleased test it out and share the result (I only have 1 Nikon thin filter which don't do well with Hoya). You will see that different brand give diff color hues, from deep purple to blue.

    Having said that, 1x linear may be fair better. But linear is not common now.

    Quote Originally Posted by giantcanopy View Post
    My slim Vari-ND works well even past the recommended 8 stops, no funkiness or cast noted. But i think (Singh Ray) themselves do not vouch for funny things that happens in that zone.

    spheredome what do u mean by 60% ?

    Alternatively u need 2 very high quality thin polarisers to DIY something like that.

    ryan

  12. #12

    Default Re: Create Fader ND out of 2 CPL Filters

    Cathay Photo sells the Genus ND Fader at a fraction of the cost of the Singh Ray one.

    http://www.cathayphoto.com.sg/offers...-nd-fader-77mm

  13. #13
    Senior Member zac08's Avatar
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    Default Re: Create Fader ND out of 2 CPL Filters

    Done this a long time ago... Linear and CPL will work properly.

    I was buying polariser filters and mistakenly bought a linear polariser instead, but well... it was good fun trying out the variable ND effect affter reading it from the net.
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  14. #14
    Moderator daredevil123's Avatar
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    Default Re: Create Fader ND out of 2 CPL Filters

    Stacking a linear polarizer in front of a CPL is the better approach. But do take note that if you stack the linear behind the CPL, you will not see any effect at all. You can try it by using polarized sunglasses(linear) with a CPL handheld.

  15. #15

    Default Re: Create Fader ND out of 2 CPL Filters

    Quote Originally Posted by tomcat View Post
    Cathay Photo sells the Genus ND Fader at a fraction of the cost of the Singh Ray one.

    http://www.cathayphoto.com.sg/offers...-nd-fader-77mm
    According to "them", it is more for videography then still photography due to the discoloration.
    Was ask not to buy by "Them" if I'm particularly concern the discoloration.
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    Senior Member giantcanopy's Avatar
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    Default Re: Create Fader ND out of 2 CPL Filters

    Quote Originally Posted by BeeHive View Post
    According to "them", it is more for videography then still photography due to the discoloration.
    Was ask not to buy by "Them" if I'm particularly concern the discoloration.
    wow "they" really said that ? there hasn't been much of user reviews regarding the Genus Fader ND, compared to the more illustruous but exorbitant SR Vari-ND. I got the later product much eariler because of lack of much alternatives to a one filter solution then. But i might have given more serious thoughts to the Fader ND.

    But I would expect people to come up with more products to compete.

    ryan

  17. #17

    Default Re: Create Fader ND out of 2 CPL Filters

    Quote Originally Posted by BeeHive View Post
    According to "them", it is more for videography then still photography due to the discoloration.
    Was ask not to buy by "Them" if I'm particularly concern the discoloration.
    "Them" being Cathay Photo?
    If so, "they" certainly didn't advised me that way when "they" introduced the product to me.
    I don't see any discoloration (greyish) whatsoever until it is turned to the absolute darkest anyway.
    In any case, doesn't colours matter in videography?
    Last edited by tomcat; 16th February 2010 at 01:15 PM.

  18. #18
    Senior Member shierwin's Avatar
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    Default Re: Create Fader ND out of 2 CPL Filters

    This article demonstrates the colour shift as the stops increase with the CPL-PL variable ND filter:

    http://dimagemaker.com/2008/02/23/us...ble-nd-filter/

  19. #19
    Moderator daredevil123's Avatar
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    Default Re: Create Fader ND out of 2 CPL Filters

    Quote Originally Posted by giantcanopy View Post
    wow "they" really said that ? there hasn't been much of user reviews regarding the Genus Fader ND, compared to the more illustruous but exorbitant SR Vari-ND. I got the later product much eariler because of lack of much alternatives to a one filter solution then. But i might have given more serious thoughts to the Fader ND.

    But I would expect people to come up with more products to compete.

    ryan
    A lot of Vari ND products have been released by chinese makers. Some claiming to use Schneider glass. The slimmer 77mm ones with Schneider glass are going for around 450 RMB (around $90-100 SGD) in China.

    And yes, I still see some color cast start to appear after 6.5 stops (naked eye, not through camera). The manufacturers only claim usability up to 8 stops. Fair enough. I also heard issues with cross-banding in some lighting situations. See:
    http://digitalphotographer.com.ph/fo...t=26001&page=5

    In the end, I did not purchase it. Opting for a B+W ND110 (also have some color cast).

    But seriously slight color cast can be taken care with WB adjustment mostly. Problem will be cross banding.
    Last edited by daredevil123; 16th February 2010 at 02:53 PM.

  20. #20

    Default Re: Create Fader ND out of 2 CPL Filters

    You people, no good lah, make me spend money. Keep introducing x and y brand, now I have to get a LCW to satisfy my visual curiousity.

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