Have you considered some sort of IR warning system?
You could have a function that detects a color balance shift between two different levels of ND, indicative of excessive IR "pollution", and post a suitable warning.
Keith... difficult trick but the boys continue to look at it.
My thought in the meantime was to do a White Balance with no filter and another with the ND in to see if there was a major change. The problem is you'd have to look at the whole image because some parts of the image may show no IR contamination (like a white polyester fabric) and other parts could show alot...like black cotton dyed fabrics. I still like the idea because it could also be used to check if your filter has a color bias in addition to being an IR filter.
One thing is certain... and tests have proven out, the new sensor and OLPF filter does a much better job with IR contamination. 1.2 ND should be no problem and 1.8 is significantly better than with the original sensor.
Edited by Jim Jannard, 18 February 2010 - 01:49 AM.