Correcting color casts in variable ND filters -- solution

Discussion in 'Image Processing' started by entropic remnants, Jul 6, 2013.

  1. entropic remnants

    entropic remnants Hall of Famer

    Mar 3, 2013
    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.