Quote Originally Posted by Robert Budding View Post
Are you correcting for reciprocity failure for those 15-30
sec exposures? If not, you will underexpose and end
up with flat negs.
Follows is my understanding.
Reciprocity's failure applies to those portions of a scene
who's level of lighting falls below some minimum. The failure
is non-linear and accelerates. So dropout increases
disproportionately with lowering light levels. An
increase in contrast occures in those low
level lighted areas. Dan