Layer mask in Elements 4.0

I use Elements 4.0. I would like to use a layer mask with a B/W negative of the actual photo. I know how to use a layer mask in Elements, but I can't figure out how to get the B/W picture into the layer mask. In fact I don't know if it's possible. I will use it to mask the highligts of a photo to correct the exposure. (I hope this makes sense).
Can someone point me in the right direction?

Carnt help you in Elements but In Photoshop , you would with your BW negative , select all , copy ,,, then go to your other document and click on the mask , Alt click on the mask itself in the layers stack , it should now open the mask as its own window and be just white , now hit paste ,, now the mask has your BW pic in it ,,, now in your Layers stack just click on the image on your masked layer , not the mask the image beside it the one the mask is working with ,, that will close the large mask window and give you a BW image on a layer mask ,,, that should be it .

Rod

Thank you Rod for a very nice explanation. I hope it will work in Elements.

Elements doesn't have image layer masks, but it does have adjustment layer masks, which can be grouped with an image layer to simulate CS2.

First, create an adjustment layer between your two image layers. I use a Levels layer with at the default settings, but it doesn't matter what adjustment layer you use since you won't be using the adjustment.

Next, group the adjustment layer with the image above it that you want to mask. I use alt-click between the two layers to group them, but you can also do this by selecting your image layer above the adjustment layer and using the "Layer...Group with Previous" (Ctrl-G) command.

Once you've done this, you can use the Adjustment Layer's mask in the same way you'd use a CS2 layer mask.

Here's what a PSE4 "layer mask" looks like when done. Here I'm using a mask to do selective sharpening on only the dog, leaving the background unsharpened...

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