Simulate shallow depth of field
Use the lens blur filter to simulate shallow depth of field
Sometimes we capture that perfect moment with our camera and then realize that the subject is not isolated enough from the background and the background is really distracting. Now what? Well, you can use the lens blur feature in Photoshop to keep the subject in focus while blurring the distracting background, simulating a shallower depth of field. Alternately, you could blur the foreground and make the background clear. The possibilities are endless.
The Lens Blur feature is not new, but the new algorithm now uses your computer's GPU to create nice blurry edges on objects in the foreground, more realistic bokeh, correct color handling for CMYK and LAB color modes, and more colorful specular highlights in your photos.
Here are 3 different methods that you might choose to set the blur from foreground to background. I will demonstrate option 2 in the tutorial.
OPTION 1- Easy (if you have the capability on your phone)
Enable the depth map on your mobile phone if it is supported. When you open your photo in photoshop, the depth map will be available in the lens blur options. In case you are interested in trying this, this link shows how to configure the camera in Lightroom mobile on a capable iPhone: Depth capture mode (Technology Preview)
OPTION 2- Intermediate
Use a gradient as a depth map to determine which areas are blurred. Create a simple gradient in the Alpha channel from white at the top to black on bottom and select it from the lens blur options.
OPTION 3- Advanced
Use an alpha channel depth map to describe the foreground, middle ground, and background. You can make several layers from selections, combine them or create a smart object, and copy the result to the Alpha layer. You can then select it from the lens blur options. This might be a good option for a portrait where the background needs varying degrees of blurring, but you want the subject to remain in focus.
Layer1: a selection of the subject in the foreground filled with black
Layer 2: a selection of the middle ground filled with grey
Layer 3: background area filled with white.
The Lens Blur filter uses the depth map from your phone camera or the alpha channel you create to determine the position of pixels in an image. The depth map is just an illustration of depth from black to white. Black areas are at the foreground at the front of the photo, and white areas are in the background.
OK, let's create a simple gradient and use the lens blur filter to change our photo.
❶ Import a photo
- Open Photoshop and import the photo you would like to edit
❷ Create an alpha channel
- Click on channels
- Click on the + at the bottom right corner to create an alpha channel
- Select the gradient tool
- Choose the linear gradient
- Choose the gradient option from white to black
- Click above the image and drag just beyond the bottom of the image to create the gradient
- The light areas will be the background, the greys will be the middle ground, and the black will be considered the foreground
- Click on the RGB channel above the alpha channel so you can see the photo again
❸ Blur the photo
- From the menu, choose Filter>Blur>Lens Blur
- In the Depth Map section, choose Alpha 1 from the dropdown if it is not already selected
- This ensures that the Alpha channel gradient you just made will be used as the depth map. You will note that the background is very blurry, the middle ground is somewhat blurry, and the foreground is clear. If you want the focus on a different area, then just click on it and the blur will change. Here is an example of the blur when the depth map was applied, when I clicked on the middle ball, and when I clicked on the 12 ball in the back. You can see how the blur changed.
- Click OK at the top right to accept the settings
Related links:
Save selections and alpha channel masks
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