transparency - Is there a way in photoshop to convert k values to alpha values?

Basically, I would like to make it so that the lighter a pixel is (the more white it has) the more transparent it becomes. Black pixels would be opaque, white pixels would be transparent.

I currently use the slider in blending options on the first tab to get rid of the white and make it transparent but find it works slightly better if I use the magic wand tool with delete.

I figure that there is some blending option out there but there are so many and I'm not sure which to use to achieve my goal.

(Using Photoshop CS6)