Quote Originally Posted by piu58 View Post
> Will this really increase contrast beyond grade 5

You don't reach grade 5 with dichroitic filters. I guess maximal filtering PLUS grade 5 filter + longer development gets one grade more than dichroitc filter alone. But this depends strongly on the paper. FOMA ist softer than MCC, for instance.
The key word is FILTER. That is what filters do, they filter out light and if all the green light has been filtered out by one filter, adding a second filter to try and filter out some more green light will make zero difference except increase print time due to added filter density.
The question is whether all the green light has been filtered out by one dichroic filter. Possibly not but it really depends on your particular enlarger so adding a second filter may have an effect but not nearly as much as you might at first think.