Fix it
ND Filter X-Cross, Colour Cast or Vignetting? Fixes (2027)
Fix ND filter problems: the dark X pattern, green and magenta casts, uneven density, vignetting and stuck filter threads.
ND problems are almost always range problems: a variable rotated past its honest stops, a stack too thick for a wide lens, or a white balance set before the filter went on. Work through these fixes in the field order below and most footage and frames are saveable without new glass.
Dark X pattern across the frame
You have rotated a variable ND beyond its designed maximum for your focal length. Back the density off until the X dissolves, typically half a stop to a full stop, and mark that real limit for this lens with tape or a note. Wider lenses hit the X sooner; on ultra-wides, switch to a fixed ND at the density you need.
Green or magenta colour cast after adding ND
Re-white-balance with the filter mounted and set, ideally from a grey card in the same light, instead of correcting blindly in post. Reduce density if the cast grows with it, and expose a touch brighter: ND casts hide in lifted shadows and scream in crushed ones. Persistent cast at moderate densities marks a filter to retire from colour-critical work.
Dark corners and vignetting
Your filter stack is too thick for the lens's field of view: remove step-down combinations, use a slim-frame filter, and avoid stacking a variable over other filters on lenses wider than about 24mm. Check that a step-up ring, not the filter itself, is not the intruding element by testing the filter alone.
Filter is stuck on the lens
Never force it with pliers on the glass. Use a rubber filter wrench or a wide rubber band for grip, apply even pressure around the ring rather than squeezing two points (which ovalises the frame and binds it tighter), and warm cold hands around the ring. Prevention is a brass-frame filter and a whisper of care not to cross-thread on day one.
Questions, answered
Why does my ND look fine on one lens and terrible on another?
Field of view and focal length change everything: wide lenses expose X-cross and vignetting, long lenses expose glass softness. Test every lens and filter pairing you own and log the honest limits.
Can colour cast be fixed in post?
Mild casts, yes, with white balance and tint. Strong or uneven casts, especially across skin mid-tones, resist clean correction, which is why neutrality tops the buying criteria in this guide.
Should I remove the ND for photos between video clips?
Only if the stills need shutter speeds the ND forbids. Many hybrid shooters leave a 2 to 5 stop variable mounted all day and ride aperture and ISO for stills within its range.