1. Reminder: Please use our affiliate links for holiday shopping!

Experimenting with ND filters for long exposures... Getting partial color casting

Discussion in 'Open Discussion' started by CARHOUND, May 4, 2014.

  1. CARHOUND

    CARHOUND Mu-43 Rookie

    18
    Apr 26, 2012
    Here's the example:

    <a href="http://gmanis.smugmug.com/OUTDOORADVENTURES/WATERFALL-GLEN-14/i-G5phRKZ/A" title="Photo & Video Sharing by SmugMug">http://gmanis.smugmug.com/OUTDOORADVENTURES/WATERFALL-GLEN-14/i-G5phRKZ/0/S/Waterfall%20Glen-50-S.jpg" title="Photo & Video Sharing by SmugMug" alt="Photo & Video Sharing by SmugMug"></a>

    I was using Hoya ND filters 6 stop+3 stop+polarizer. Shot on a GX1 w/ 14-45 with hood.

    I had shot several other long exposure shots during the day, and in that same position and the majority came out just fine. I was trying out a variety of aperture settings to see the effect on the running water. There were some instances of my accidentally jostling the camera, not sure if this is one of them.

    The only other explanation was that I maybe caught some reflections between the filters? I did a little googling and couldn't find anything conclusive.

    Any thoughts?
     
  2. OzRay

    OzRay Mu-43 Legend

    Jan 29, 2010
    South Gippsland, Australia
    Ray, not Oz
    That really is far too many filters stacked together, you'd be better off getting an 8 stop ND and working just with that. Some ND filters aren't always absolutely neutral and can cause colour casts in the shots. Also, Have you tried without the polariser, as that is very likely to also cause problems?
     
  3. tosvus

    tosvus Mu-43 Top Veteran

    632
    Jan 4, 2014
    Polarizers are not uniform in brightness on wide lenses. Maybe that and some weird effect due to combining???
     
  4. budeny

    budeny Mu-43 All-Pro

    Mar 4, 2014
    Boulder, CO
    Auto WB? Have you checked if WB differs from shot to shot?
     
  5. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    Its an interesting problem. I agree with ozray at too many stacked is a bad thing, it could well be e internal surfaces reflections you mentioned. Was it AWB?

    Nice shot too :)
     
  6. pdk42

    pdk42 One of the "Eh?" team

    Jan 11, 2013
    Leamington Spa, UK
    NDs at that level of blocking often have colour casts. It's best to buy the best and don't stack if you want to avoid casts like rhis.
     
  7. speedandstyle

    speedandstyle Mu-43 Hall of Famer

    Very few ND filters are 100% neutral and thus have a slight color cast but they are always even across the frame{unless it is a graduated ND}. I don't think the stacking caused this. I have used multiple ND filters stacked and never had any problem.

    What aperture did you shoot at? I have heard of some ND filters when stopped down a lot{f16+} causing extreme color casting because of diffraction. With the long exposure the colors get very saturated as in the example you show.
     
  8. janneman

    janneman Mu-43 Veteran

    414
    Dec 6, 2012
    Netherlands
    Jan (John) Kusters
    I expect the polariser is bringing out a problem in the neutral density Filter. Stacking filters is not optimal to begin with, but usually it is not that bad (see the very funny and informative articles Mr. Cicala wrote on the subject, like http://www.lensrentals.com/blog/2011/06/good-times-with-bad-filters). Using a polariser as one of those stacked filters, chances are there will be more trouble.
    With laminated filters (filter material wedged between two sheets of glass) the bonding between layers might be less then perfect, and the polarisers is bound to show that.
     
  9. CARHOUND

    CARHOUND Mu-43 Rookie

    18
    Apr 26, 2012
    Exactly, if it was over the whole shot then yeah I would look at the ND filters as the issue. I looked at the shot data for the shots with this particular problem and while I would need to check more to confirm my findings but this seemed to only have happened when I stopped down significantly f16+

    Probably a combination of internal reflections and diffraction as in all the problem photos it only occurs over portions of sky visible in the frame.