I'm working in Photoshop to add sun beams to a B & W landscape. I've added them successfully but I've come up against a brick wall trying to erase unwanted beams. The procedure I'm following is to set the brush tool to black, set opacity to 50%, set brush size to 300px and set hardness to zero percent. These seem to be the standard settings according to several tutorials I've been watching. However, it is not working for me, it just adds paint to the image, when it is supposed to have an erasing affect. Also, in my CS4, I've found that the only way to get the brush to appear is by merging the layer first, without merging, only the little "can't do" black circle with diagonal line through it appears. Has anyone done this before ? I'd be thankful for some guidance to get this sorted out, it's the last step to finish the photo and it's a little frustrating that I can't finish it off perhaps because of an oversight, which I wouldn't be aware of anyway.