Depth of field blur

Open up landscape photo ie Petworth House

Duplicate layer

Open Channels panel in windows drop down and open up Alpha 1 channel by clicking plus. This will also turn off RGB,R, G, B channels.

Use the gradient tool. In the drop down next to swatches, select basic and the middle one which is a black to white gradient. Click reverse in options so it will be a white to black gradient. Draw down a white to black gradient in the black alpha1 panel from above top to below bottom Now click on RGB which will switch off Alpha 1 channel and tick the RGB, R, G, B channels on again. you don’t need to close the Alpha 1 channel , just leave it switched off.

Selecting the top layer filter-blur-lens blur

A new workspace will open up click preview and faster and make sure source is Alpha 1

Set focal point becomes darker when switched on and you then click the part of the image you want in focus. The radius slider is used to determine how much you want in or out of focus. The higher the radius the more out of focus.

The end result is a shallower depth of field.