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Correcting color casts in variable ND filters -- solution

Discussion in 'Filmmaking' started by entropicremnants, Jul 6, 2013.

  1. entropicremnants

    entropicremnants Mu-43 All-Pro

    Jul 16, 2012
    John Griggs
    Some of us want to use variable-ND filters to allow our cameras to shoot video wide open in bright light at slower shutter speeds -- or to shoot at all wide open.

    The problem is that almost all variable ND filter create an odd color cast that is difficult to impossible to properly correct with the temperature/hue controls.

    Turns out that using the RGB channels and then touching up temperature solves the problem as detailed by Dave Dugdale in this article:

    Variable ND Filter Shootout

    Basically, raise the blue channel a bit, maybe the green too for some filters (for mine, yes) and then touch up white balance and you can get perfect color.

    In my stills photography I haven't ever had to manually balance R/G/B channels singly to get color right but maybe I've been lucky, lol. At any rate, I did not think to do this and version 1 of my short "Flying Patriot" I made certain scenes black and white to dodge the issue.

    Now I can redo it in color.

    Hope this helps someone else as much as it helped me, lol. Now I can keep that filter and use it when I need it -- but with proper adapters so I don't get vignetting.
     
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  2. Dramaturg

    Dramaturg Mu-43 Top Veteran

    614
    Jun 7, 2013
    Ukraine
    Yevgen
    Just wonder - why wouldn't you correct colors in PP? Most movie editing software allows you to do the same stuff you do LR, etc. Sony Vegas, for example, has great color correcting and split toning presets.
     
  3. entropicremnants

    entropicremnants Mu-43 All-Pro

    Jul 16, 2012
    John Griggs
    That's exactly what is being done -- correcting in post. Not sure what you think was being proposed, lol.

    However, this particular color cast doesn't respond well to automatic color correction or typical "white balance" adjustment controls, hence using the RGB controls for correction.

    Split toning has nothing to do with this. It's strictly a color balance for a color presentation.
     
  4. Dramaturg

    Dramaturg Mu-43 Top Veteran

    614
    Jun 7, 2013
    Ukraine
    Yevgen
    I see :). Thought you speak about in camera corrections.

    I use split toning to give my footage that cinematic or retro looking colors. Pretty much the same as in the LR - give more yellow to highlights and magenta to darks. Anyway, now your post makes sense for me :)
     
  5. entropicremnants

    entropicremnants Mu-43 All-Pro

    Jul 16, 2012
    John Griggs
    Ha ha! Cool.

    With regard to split-toning -- I only know that from black and white processing. Are you using it on color footage then? I've never done that. Sounds interesting.
     
  6. Dramaturg

    Dramaturg Mu-43 Top Veteran

    614
    Jun 7, 2013
    Ukraine
    Yevgen
    I do use it on color footage (the only footage my OM-D produces :smile:). I do editing in Sony Vegas and there is a split tonint color correction preset where you can, basically, create that retro look for your footage. For example, this video done by my friend is split toned the same way - [ame="http://vimeo.com/74094688"]http://vimeo.com/74094688[/ame]

    The logic is the same as in Light Room. Playing around with split toning you can give a special feel to your footage.
     
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  7. woof

    woof Mu-43 Top Veteran

    511
    Oct 18, 2011
    The present.
    Yes, big help. I more recently adopted the Hoya ND400 9 stop, and in limited testing under mostly cloudy conditions it seems relatively unaffected. My Big Stopper on the other hand... especially when combined with other filters.

    Seems the threshold for strong color cast is at >= 10 stops? In any event, I kind of stopped using my Lee except situations where I know I'll convert to B&W, and this is relatively rare for me... so this may rehabilitate that tool. Thanks kindly.
     
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