Quick and dirty way of adding depth of field to an image is by creating a gradient blur effect using a blur mask, levels and the gradient tool…

1] Duplicate the image layer you want to add the blur to

2] Layer > New Adjustment Layer > Levels… to create a levels adjustment layer

3] Press ‘G’ to select the gradient tool. Choose the Black to White gradient from the gradient select panel

4] Click with the Gradient Tool in the area you want to remain in focus and drag to where you want it to be out of focus. Use a shallow gradient for a more dramatic blur effect

5] Control click and hold on the layer mask thumbnail to load the gradient as a selection

6] Click the Background layer and select Filter > Blur > Lens Blur (not Gaussian)

7] Drag the slider to adjust the amount of blur and click OK

8]  Ctrl+D to deselect the area.

Finished effect should look like this…

…from this original image…

If you want more realistic depth of field effect or perhaps to recreate extremely shallow focal depth on an area of your image (like with a macro lense) , then you should use the lens blur tool again and choose the reflect gradient type. Will post this, along with the reason why you should use lens blur rather than Gaussian in part 2 of this hint.

Easiest way to do this is to use the Advanced Blending options on a layer placed directly above the image you want to knock-out.

1/ Place you image on a new layer  or double click on the background layer to turn it into a proper layer

2/ Insert a new blank layer above your image  -(you can just click the ‘create a new layer’ icon next to the dustbin at the foot of the layers pallet) and rename it ‘knock out gradient’.  keep the knockout gradient layer selected

3/  Select the gradient tool, if necessary click the linear gradient button and select the default foreground and background colours(to set foreground to black and background to white)

4/ Click the arrow to the right of the gradient display in the options bar to open the gradient picker, then choose the ‘foreground to transparent’ gradient  (by default, this is usually the second gradient in  the gradient pallet)

5/ Click, shift and drag from the bottom of the image to the mid point, to create a gradient to go from black at the bottom of the image to transparent at the top.

6/ In the layers pallet, click Layers style ‘Fx’ option and choose blending options (double clicking the layer also brings up the layer style options)

7/ In the advanced blending panel, drag the ‘fill opacity’ slider to zero percent. Change the knockout drop down from ‘none’ to ‘deep’. (note: ‘deep’ knocks out to the background,  choose ‘shallow’ to knock out just the layer below

8/ click OK to apply the blending options

Share/Save