HOW TO USE DEPTH MAPS FOR THE DEPTH OF FIELD BLUR IN PHOTOSHOP TO CHANGE A PHOTO’S FOCUS

To create a bokeh effect with a shallow depth of field, we’ll use depth blur. Create a depth map as the output, and then edit the depth map. For a really realistic depth blur effect, use lens blur.
This is a more difficult tutorial that will yield the best outcomes. See this tutorial for a quicker, easier method to add background blur to a plain photo without utilising depth maps.

Choose Filter>Neural Filters

Choose Depth Blur, you will see the background becomes blurry.

In the thumbnail on the right, click the background.

Watch how the background sharpens and the train blurs.

In the thumbnail, click the train’s front.

It appears fairly realistic. However, the spaces in between the poles on the right were overlooked.

The difficulty with AI-based blurring is that occasionally minute details are overlooked.

Let’s take control of the blur.

At the bottom, click Output as Depth map only. The preview image will turn into a grayscale Depth Map.

Click ok.

Now that we have a depth map in grayscale, we can utilise it to concentrate the blur.

The software knows that the darker regions should be sharper because they are closer to the camera. The brighter regions ought to be less distinct.

Hide the top layer and click on the bottom layer

Choose the quick Selection tool.

With the selection active, turn the top layer back on and make sure it’s the active layer.

Pick up a paintbrush.

Click and hold Alt or Option to view a colour sample.

Paint in the bright tone after taking a sample of it.

Notice, I painted 3 tones into the selection, so that it matches the rest of the image in the depth map. Press Cmd/Ctrl+D to deselect

From the depth map, we will create a channel so that we may use it.

Activate the Channels panel. Window>Channels

To duplicate the red channel, drag it into the Plus icon.

It is an alpha channel and goes by the name Red Copy.

By double clicking the name of the channel and entering a new name, you can alter it if you’d like. It now goes by the term DM, or Depth map. The names serve only to make it simple for you to recognise the alpha channels.

Re-select the RGB channels by clicking on their names; the DM channel should be disabled.

Hide the depth map layer.

Duplicate the background if you want, just as a best practice, to preserve the original layer.

Choose Filter>Blur Lens Blur

You will see a Depth Map option. Change source to DM, if it isn’t already selected.

We can now use this depth map channel to blur the image.

Choose the cross hairs. (Set focal point)

Select the portion of the image that you wish to be crisp by clicking. To blur the background, alter the blur’s strength.

Here is our incredibly realistic outcome.

I hope you found this tutorial useful