Quote Originally Posted by David Allen View Post

The filter that I most used when doing landscape photography was a Wratten #12 (Minus Blue) filter. This filter looks yellow but is actually a special formulation for B&W that markedly lowers the tonal value of blues without affecting the other colours. It produces results similar to a red filter but far more subtle, removes haze, takes the blue out of deep shadows thereby creating more visual contrast and, all of this, with only a loss of one stop. The Minus Blue filter proved invaluable in getting good representation of landscape tonality in the UK, Brazil, Chile and Germany.
Is this the same as a #12 Deep Yellow filter?

I have a yellow-green filter that I like using in shots where I don't want to suppress the foliage but want a darker sky. I don't generally like stacking filters as it tends to lead to unpredictable results.