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Variable ND Filter Trouble

Discussion in 'Help and Feedback' started by KillRamsey, May 20, 2014.

  1. KillRamsey

    KillRamsey SC Hall of Famer

    Jun 20, 2012
    Cambridge, MA
    Kyle
    This is probably something simple, but it's my first variable ND filter experience, and it ain't going so hot so far. I stopped this morning on the way in to work, set up a tripod, put the 14 on the XT, and took this. I noticed it on the rear LCD, and thought "uh oh. Maybe it's just on the LCD and won't be on the image?" But of course it is.

    DSCF2910.JPG

    Lightening up the ND filter to around 4 stops, it diminishes but isn't gone...

    DSCF2914.JPG

    So what causes this? I know about circular vs linear polarizers, but have never heard of ND filters having the same potential issue.
     
  2. Luke

    Luke Super Moderator

    Nov 11, 2011
    Milwaukee, WI USA
    Luke
    I haven't seen this before, but think about how a variable ND filter works (not that I really know), but it is 2 polarized pieces of glass rotating and the various levels are from the resulting darknesses of the 2 different pieces aligning. Not sure if you were just "between" two settings or if it defective. I'd set up a tripod and fire off a few shots at different settings and see if you can have any success. If you can't (or it isn't easily repeatable every time), I'd send it back and get a 10 stop ND filter from a quality filter maker for when you need the "effects". And then a 3 stopper for more normal uses like shooting wide open in sunshine.

    p.s - the second shot shows dust spots on your sensor in the sky. (sorry for the misplaced metaphor {or is that a dangling participle}....obviously your sensor is not in the sky)
     
  3. Pim

    Pim SC Regular

    157
    Apr 21, 2012
    Eindhoven, The Netherlands
    Pim
    I very briefly owned a variable ND filter and got the exact same effect with anything above 3 stops or so... I did some research and found I was not alone in experiencing this. Maybe the filter was not of sufficient quality (I cannot remember the brand but it certainly was not the cheapest one), but needless to say I returned it and got a fixed filter instead.
     
  4. KillRamsey

    KillRamsey SC Hall of Famer

    Jun 20, 2012
    Cambridge, MA
    Kyle
    Luke the dust is on the filter. It showed up on several shots, and vanished on others as I rotated the filter around. So it's on the front element somewhere, but because the damned thing is so dark I didn't notice it was smudged. I blame my 4 yr old. And I tried shots all the way from full 8 stops to just 2 stops, and the effect gradually comes on in a smooth manner. So it's not at just one specific spot in the range of filtering.

    Crap.
     
  5. Luke

    Luke Super Moderator

    Nov 11, 2011
    Milwaukee, WI USA
    Luke
    Kyle, if your front element is smudged, feel free to blame your 4 year old (though from the photos I'm fairly certain she is an angel).

    But dust on a filter or a lens ALMOST never shows up in a photo. At least I have never seen it. The dust on the sensor will only show up when stopped down. Also, the dust removal mechanism in the Fuji may shake it loose so sometimes the dust spots move around from to time.
     
  6. KillRamsey

    KillRamsey SC Hall of Famer

    Jun 20, 2012
    Cambridge, MA
    Kyle
    Many of these were shot at f22. And I think those are dirty fingerprints, not tiny specs of dust.
     
  7. KillRamsey

    KillRamsey SC Hall of Famer

    Jun 20, 2012
    Cambridge, MA
    Kyle
    ...doing an experiment now...
     
  8. Luke

    Luke Super Moderator

    Nov 11, 2011
    Milwaukee, WI USA
    Luke
  9. KillRamsey

    KillRamsey SC Hall of Famer

    Jun 20, 2012
    Cambridge, MA
    Kyle
    It isn't the ND filter. Dang. Shooting the white ceiling above my desk, I went through f22 all the way in whole stops down to 2.8. Dark blemishes clearly visible at f22, fading down to f11, gone at f8 and below.

    ?!
     
  10. Luke

    Luke Super Moderator

    Nov 11, 2011
    Milwaukee, WI USA
    Luke
    it's the joys of interchangeable lens cameras.

    But at least you can access the sensor to clean it.....in the rare instances that this happens with a fixed lens camera, you're just out of luck.
     
  11. KillRamsey

    KillRamsey SC Hall of Famer

    Jun 20, 2012
    Cambridge, MA
    Kyle
    I just put the 27 pancake on it, and went through the same deal. No spots whatsoever, even cranked down to f16. Soo... back element of the 14 is dirty?
     
  12. john m flores

    john m flores SC All-Pro

    Aug 13, 2012
    I struggled with college physics when they got to light (wave nature, particle nature, let's call the whole thing off!), but the idea of stacked rotating polarizers never struck me as a good one. You're not likely to get even transmission, but that does depend upon the light source.
     
  13. Luckypenguin

    Luckypenguin SC Hall of Famer

    Dec 24, 2010
    Brisbane, Australia
    Nic
    Polarisers on ultra-wide angle lenses can cause problems because the change in polarisation as the angle to the sun changes is very noticeable.

    The larger smudges seem too big to be dust on the sensor, although the smaller dots may well be. Do you get the same effect using the 14mm lens without the variable ND filter attached?
     
  14. KillRamsey

    KillRamsey SC Hall of Famer

    Jun 20, 2012
    Cambridge, MA
    Kyle
    Regarding "do you get same effect without ND filter", the smudges DO still happen on the 14 when it is stopped way down. The banding thing, obviously not.

    I wrote B&H to ask if I could send them a few sample images and ask for help. If this is just par for the course with the 14 because it's wide, then can I safely assume that a static 10 stop (for example) ND filter would work ok?
     
  15. KillRamsey

    KillRamsey SC Hall of Famer

    Jun 20, 2012
    Cambridge, MA
    Kyle
    Holding the ND filter in front of the 27 pancake, when I crank it to 8 stops dark, I can clearly see the same dark angled banding. As I rotate the filter around (not changing the darkness, just rotating the whole assembly) I can see the "X" rotating.
     
  16. kyteflyer

    kyteflyer ~@¿@~

    Jan 31, 2011
    Newcastle, Australia
    Sue
    Using any kind of variable filter is fraught if your lens has a front element that rotates. I have a couple of ND filters, an ND8 and an ND400, and I wanted to get a graduated ND filter, too, but I've found that the graduated filter of Nik Color Efex Pro works just as well, in post, as it would on camera at the time, so I don't fret any more about having an area of a photograph slightly overexposed (usually happens to skies, when I am trying to get foregrounds)
     
  17. KillRamsey

    KillRamsey SC Hall of Famer

    Jun 20, 2012
    Cambridge, MA
    Kyle
    Research and a response from a B&H cust service rep confirms that "this just happens with all variable ND filters," pretty much.

    Why
    Do
    They
    Sell
    Them

    So now I'm going to have to return it for a static one, 8-10 stops I guess, to be able to do long exposure landscapes. Hopefully with some step-up rings I can also use it with other lenses.
     
  18. Djarum

    Djarum SC All-Pro

    Jul 10, 2010
    Huntsville, AL
    Jason
    This is typical from what I've read about various brands of variable ND filters. Most exhibit this issue. I've read about this issue using a circular polarizer stacked onto a linear polarizer as well. Same effect I believe.
     
  19. NightBird

    NightBird SC Regular

    175
    Apr 23, 2013
    Sydney, Australia
    Darren
    I Just tried the a standard Hoya HD polarizer on my XF 14 and had a similar, though much less severe result. I remember on my Nikon 11-16 I used to have the same problems also. I just stopped using them for the most part on wide lenses. It does depend on the angle of light as well.

    I've read that this is quite common and somewhat normal with wide angle lenses.
     
  20. Luke

    Luke Super Moderator

    Nov 11, 2011
    Milwaukee, WI USA
    Luke