Quote Originally Posted by Roger Cole View Post
There is that, granted. TMX and TMY are pretty good WRT reciprocity failure too but they're not Acros. I think the suggestion that TMY is slower than TMX in long exposures has been refuted, at least until they get VERY long. TMY-2 might actually lead to shorter exposures than Acros though I'm far from sure of that, and that doesn't address the need to figure the compensation nor the impact on contrast.
While Acros holds up better than TMY2, the exposure duration for TMY2 at EI400 will always (for exposures shorter than one night) be shorter than for Acros. But you'll get less contrast-increase from the Acros.