There are already some very useful methods for black and white conversion including the new channel mixer with PWP 5.0. I offer another that I have found gets me to a useful starting point very quickly for landscape images.
Use the "Extract Color Channel" transformation to extract the Red Channel
Use the "Extract Color Channel" transformation to extract the Luminance Channel
Open the "Composite" Transformation with the Red Channel as the input image and the Luminance Channel as the overlay image.
Choose "Soft Light" for Mode
I often find that the result is black and white image with contrast the way that I like it. You can choose "Hard Light" for a little more contrast or "Blend" for a little less.
Black and White Conversions
Moderator: jsachs