I looked the filter up and found the following: This filter is frequently described as a heat absorbing filter because it lets the visible spectral range pass while the infrared rays from 780nm are strongly blocked. It is often used to protect IR-sensitive CCD sensors or in illumination systems.(posted 8585 days ago)Obviously, it must also block some visible red spectrum. It would make sense that its factor would be higher for Tech Pan, since Tech Pan is more red-sensitive. This would cut the effective speed of Tech Pan down to EI 6 or 12. Still, it would be worth trying. I keep looking for some way to make this film work for me.
Using a red filter: There is a lovely photograph in the latest issue of View Camera (March/April 2001) by Don Kirby (page 15) of a field of mown bluegrass that was taken with Tech Pan in 6x9 format. It is a remarkable image. He used a deep red filter and developed in Rodinal (1:200) for 19 minutes with periodic agitation. He says this is an N+2 development.
When I tried a red filter with Tech Pan and developed in Technidol liquid, the negatives were so contrasty as to be unprintable.