Photoshop Tutorials: Shadowy, Sultry Eyes
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Step 2: Select Both Eyes With The Lasso Tool
Grab the Lasso tool from the Tools palette or press L on the keyboard, and then draw a selection around one of the eyes. When you're done, hold down Shift to add to the initial selection and select the second eye as well. Holding Shift tells Photoshop not to throw away the selection around the first eye when you begin selecting the second one:

Step 3: Paint With Black Along The Top Edge Of Both Eyes
We're going to add shadows to the tops of the eyes. Make sure the "shadow" layer is selected in the Layers palette, then grab the Brush tool from the Tools palette or press B on the keyboard to select it. Use a fairly large, soft-edged brush, somewhere around 40-50 pixels depending on the size of your image, and paint along the top edge of both eyes to add a shadow. Don't worry about painting above the eye by mistake because the black will only appear inside the selection we created:

Step 4: Change The Blend Mode To "Multiply" And Lower The Opacity
With the shadows painted, change the blend mode of the "shadows" layer from "Normal" to Multiply and lower the opacity of the layer to around 40%:

We don't need to have the eyes selected anymore, so press Ctrl+D (Win) / Command+D (Mac) to deselect them.