Lachlan Young
Member
yes, Thank you Matt. that was the magic needed to find the post.
the item was as I Half remembered it, https://www.photrio.com/forum/threads/fp4-and-fp4.100401/#post-1330429 so yes, the half I remembered wrong is that their may be indeed some chemical differences. BUT not so much of a difference as to create a FP5 and HP6.
Which would tally with reformulation to get to the same sensitometric & colour sensitivity end points, with improvement in granularity, sharpness & emulsion durability.