Many of my photographs require no filters but when I have had to use them I have found that my equipment (mainly a Mamiya C330f and a Speed Graphic) with TX, or HP5 (both rated at ISO 200) require at least one more stop increase than those listed in the Gordon Hutchings listings. Also, they do not seem to agree with the classical listings in general.

Anyone know what equipment and procedures were used by Hutchings in composing this listing?

There's nothing so satisfying as personal testing, providing you don't let it take over your life.

Truly, dr bob.