Psst guys don't let Tom A know I told you this but the Rollei Superpan 200 shot with a 665 filter and developed in a Beutler C(oarse) G(rain) variant comes close to HIE. I just ordered the filters and will try it out myself.
SHHH Don't tell Tom
Efke is a-flippin beautiful! I've shot 3 rolls of it metering it at ISO 4 plus 2 stops in HC110 dilution B for 7 mins with a B+W #92 near-opaque filter and am getting consistently good exposures without needing to bracket. Can't post any at the moment cause I can't suss the scanner but will do soon enough. But yeah you do need a still day without any wind or bright conditions if you don't want a swirling vortex of swaying tress.
See, thats the secret I won't tell you
Tom recommends setting the ISO to 800 (TTL). I havn't recieved my 665 filters yet so I can't really comment more. Where are those ¤¤#!**^% Filters.
Kind regards
I use an Nikon F100 for my IR-photography and it is pretty sensitive to some of the IR which means I can easily measure throught the 665-filter, just have to compensate the ISO rating on the camera.
With Superpan 200 and Beutler GD, I use an ISO settings of 800 which gives me shutter speeds around 1/125 to 1/250 at f:8.