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Filter problems

Discussion in 'Help Team' started by Stepbel, Jun 8, 2017.

  1. Stepbel

    Stepbel New Member

    Hi all, can anyone tell me what could be the problem, if there is one. I bought a new filter setup, a holder with integrated polarizer, a 10 stop and a 6 stop ND square filter for it. When looking in live view, if I rotate the polarizer, I can see what can only be described as 2 areas on opposite sides of the frame, at maybe 1 stop less exposure, rotating around the edge on the screen. I know this effect isn't just polarization taking place, theres something else. Has anyone any idea what is wrong? Any help would be appreciated

    PS this effect doesn't happen with the polarizer is on its own, or if the ND filter is on its own, its only when both are used together
     
  2. PeteRob

    PeteRob Well-Known Member

    two questions really. First what is the make - is it something off eBay or a major brand. Second what are you looking at and through what lens?

    Polarisers do give uneven light transmission - that is their point - and on average they block light by 5/3 stops.
     
  3. cliveva

    cliveva Well-Known Member

    my understanding of using filter sets, is to adjust the polariser first, then add in the ND.
     
  4. Stepbel

    Stepbel New Member

    They're the Firecrest ones from Hitech. I hope these images manage to get uploaded. Forgive the content, its just to show the difference. In the polarized image, the drop in exposure can be seen to be approx. 1 stop less in the bottom left and top right. Hope I haven't broken any rules with these images btw nopolar.jpg Polar.jpg
     
  5. PeteRob

    PeteRob Well-Known Member

    Firecrest are supposedly very good. It looks like physical vignetting. If you turn the holder through 45 degrees anticlockwise ( looking into the picture) does it go away?
     
  6. Stepbel

    Stepbel New Member

    Turning the holder makes no difference, at the start I thought it was vignetting too. Its only if I spin the polarizer does it move the darkened area. Its certainly correctable in post, but theyre not the cheapest filters in the world, I really shouldnt have to. I was using a cheap Haida 10 stop screw on ND filter and a screw on Hoya polarizer before this, and never had any issues. I really should try get a video of it in action and post it. Thanks for the replies

    Sorry PeteRob, I cant remember what I focused on, I just stuck the tripod at the front door and shot. Was using a 17-40L on a 6D
     
  7. PeteRob

    PeteRob Well-Known Member

    Try putting the raw file into DPP and applying lens corrections to see what happens. Possibly the filter is accentuating the normal lens fall off. I just changed my 17-40 for a 16-35 F4 and there is a big difference between the two. I bought some Lee filters and it was recommended to get the wide filter holder, which mounts the adaptor ring just behind the lens front, to avoid vignetting.
     

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