I have ProShot the full version ( on sale for 0.99c) for me as a photographer I want to see the scene in B&W before I make the photo
that way I can see what I'll get and not be distracted by colour. Nokia Creative Studio has Silver as a choice to turn a colour pic into a B&W, I
did use that then I edited to create more or less contrast. But with ProShot you can adjust contrast level before you make the photo and B&W
is largely about contrast so I find it most useful.