Adobe Photoshop Tutorials: Dramatic Black & White Effect
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Step 8: Add Another New Layer To The Top Of The Layers Palette
With the gradient layer still selected, click on the New Layer icon to add another new layer at the top of the Layers palette. You should now have four layers:

Step 9: Drag Our A Selection With The Lasso Tool
Grab the Lasso tool from the Tools palette, or press L on your keyboard to select it:

With my Lasso tool selected, I'm going to drag out a selection around the woman's hair and upper shoulders. There's no need to be surgically precise with the selection, so the Lasso tool will work fine:

Step 10: Fill The Selection With A White-to-Transparent Gradient
Grab your Gradient tool once again, then press X on your keyboard to swap your Foreground and Background colors so that white is your Foreground color. Click on the gradient preview area in the Options Bar to again bring up the Gradient Editor.
This time, click on the Foreground-to-Transparent gradient in the list of preset gradients to select it. It's the second one from the left, top row:

Click OK to exit out of the Gradient Editor, then with the new layer selected in the Layers palette, I'm going to drag out a gradient starting in the top left of my selected area and dragging down towards the bottom right:

When I release my mouse button, the selected area becomes white in the top left and gradually fades to transparent in the bottom right. I'm going to deselect my selection using the keyboard shortcut Ctrl+D (Win) / Command+D (Mac), and now here's my image with the new gradient applied:
