1. Field of the Invention
The present invention relates to an image pickup apparatus, a control method for the image pickup apparatus, and a storage unit. More particularly, the present invention relates to an image pickup apparatus such as an electronic still camera or a video camera, and a control method for the image pickup apparatus, and a storage medium that stores a program for controlling the image pickup apparatus.
2. Description of the Related Art
In recent years, many image pickup apparatuses such as digital cameras or digital video cameras are provided with functions for performing image processing on a region other than an object of interest. For example, as one of the functions, there is a function for giving a pseudo blurring effect to a background region of picked-up image data, for example.
Generally, if an image pickup apparatus has a large image sensor like a single-lens reflex camera, the depth of field becomes shallow by opening an aperture to make the focal distance longer, and it becomes relatively easy to pick up the image data that has a blurred background other than the object that is in focus as described above.
On the other hand, in an image pickup apparatus having a small image sensor such as a compact digital camera, even if the above-described method is employed, the depth of field tends to become deeper, and as a result, it is difficult to pick up the image data with a blurred background.
In view of this fact, it is known that even the image pickup apparatus having a small image sensor such as a compact digital camera can acquire image data with a blurred background, by discriminating an object region from a background region of the picked-up image data, and performing the filtering processing on the background region.
Japanese Patent Application Laid-Open No. 2007-124398 discusses a technique for acquiring a spatial frequency component from the picked-up image data, in order to discriminate an object region and a background region. That is, in the technique discussed in Japanese Patent Application Laid-Open No. 2007-124398, a blur amount on the background side of the picked-up image data is increased by adjusting the position of a focus lens so that the object is positioned at rear end of the depth of field. Then, a spatial frequency component amount for each of a plurality of segmented blocks is calculated, and a block of which value is equal to or greater than a threshold value is discriminated as the object region.
However, in the technique discussed in Japanese Patent Application Laid-Open No. 2007-124398, there is a problem that sufficient accuracy cannot be obtained if a blur amount on the background region side is small, since discrimination between the regions is performed from the space frequency component amount of one frame of the image data. In particular, in the image pickup apparatus having a small image sensor like the compact digital camera which is in widespread use in recent years, there is a tendency that sufficient blur amount is not obtained even when the above-described processing is performed. As a result, it is difficult to perform discrimination between the regions from the space frequency component amount of one frame of the image data.