Correcting color casts in variable ND filters -- solution

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

  1. entropic remnants

    entropic remnants SC All-Pro

    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.