Often, you will have the following problem with your images: Your photo shows an object, an animal or a person you want to focus on. However, both the object and the background appear sharp. It is a good idea to bring the target object into focus by blurring certain areas of the background, while keeping the target object sharp. Thus, the depth of field of the background should be changed. The background-blur-function of the post-matting-menu helps here.
In the examplary image you can see two flamingos which are obviously the target object of the photo. However, the background is also sharp. It should now be blurred slightly to focus more on the flamingos. If you select Lens Blur after the matting-process from the post-matting-menu, the Lens Blur menu appears:
(1) Radius Range: Here, you can use the slider to define the radius of the blur effect. As you will see, a high value increases the blur-effect of the background.
(2) Highlight: Use the highlight-slider to define how much the highlights in the background, i.e. bright image areas, will be enhanced. In the examplary image, these are the bright areas in the water where the sky is reflected. A high value makes these areas appear even brighter and thus emphasizes them.
(3) Aperture Shape: Here, you can change the lens-shape to change the type of blur-effect. Try the different shapes until you find one that suits your needs.
(4) Rotate Mask: Use this slider to change the direction of the blur-effect to anything between 0 and 360 degrees.
(5) Depth-mode: In depth-mode, you can switch between "Plain", "Horizon" and "Tunnel". Select "Plain" to get a smooth blur-effect across the entire background. Select "Horizontal" to obtain a different amount of blur-effect for background-areas closer the front compared to those that are further away. Select "Tunnel" to blur certain areas in the background. The grid below allows you to specify the area or, if you select "Horizontal", the position of the horizon from which you want to blur or sharpen. In our example-image, we select "Horizontal" to keep the areas closer to the target object, i.e. approximately the area in front of the flamingos’ legs, sharp and to blur the more distant areas in the background. With the grid we determine the distance from which the background image should be blurred: Experiment with these options first to become familiar with the features and to understand the effects they have on your images.
(6) Focus (close to far): This slider allows you to reverse the depth-of-field-effect. For the example-image, in which the horizontal depth-mode made the background-areas closer to the front sharp and blurred the more distant areas, a change from focus (close to far) from 0 to 100 would completely reverse the focus area. The close background-areas would become blurred and the distant background-areas would become sharp.
When you are satisfied with your depth-of-field-effect, click "Apply" and then "OK".
In the case of the sample image, the result is as follows: As you can see, the close background-areas and the flamingos are sharp, i.e. in focus, whereas the more distant areas in the background are blurred.In addition, the cropping-result, i.e. the two flamingos with transparent background, is now available in the layer-area.
This way, you can continue with the extracted object afterwards (edit, save etc.) if you don’t like the soft background. To display the flamingos without background, simply deactivate the background layer by clicking on the “Eye symbol”.