You can use depth masks in Photoshop CC to simulate a shallow depth of field created by a wide aperture of the lens. This technique is useful if you shot your photo with apertures like F8 or above and you want to create the effect of having a F2.8 lens.
The main idea is to create a layer with black and white tones that will be used as a depth mask. The black means that area will be in full sharpness, the white means full blur and the gray tones are in between. After you create this mask and you decide what elements of the photo will be in sharp and what will be blurred you create a duplicate Channel in Photoshop with this layer. Then, of course you make this layer not visible and with the main photo layer selected you apply a Lens Blur.
You’ll have the option of selecting a Depth Mask and you’ll use the Channel that you previously created especially for that. Now you can make adjustments of how much blur you want and also you’ll see if the Depth Mask works or needs adjustments.
This Photoshop CC technique is powerful and yet simple to use and apply and can create great effects on your photos!