Variable ND and IR Pollution on an AMIRA

I was DP-ing a recent short film, shooting on an AMIRA with a set of Cooke S4/i Primes. We were trying to achieve a shallow depth of field in broad daylight for some exterior scenes, which meant opening up to T2.8 or T4.0. To manage the exposure, I opted for a Tiffen Variable ND filter, thinking it would be quicker for run-and-gun adjustments than swapping individual IRND filters.

What worked well was the speed; we could quickly dial in the exposure as the light changed, which was a huge time-saver given our tight schedule. The shallow depth of field looked great, and the AMIRA handled the highlights beautifully.

However, what didn't work so well was the unpredictable IR pollution, especially at higher ND strengths. Even with the AMIRA's internal IR cut, the variable ND, particularly the older generation I was using, introduced a noticeable color shift, pushing greens and blacks into a murky brown or magenta. It was subtle on set but became more pronounced in post, requiring significant color correction to neutralize. In hindsight, I should have stuck to a set of Schneider Platinum IRNDs, which offer consistent IR filtration without the variability trade-off.

Has anyone found a variable ND that consistently handles IR pollution as well as dedicated IRNDs, even with cameras that have good internal IR filtration?