Your have a couple of options when it comes to defocusing your subject. One is to stay with selective focusing, but shift the focus points from your subject onto parts of the foreground or background. This has the effect of making the defocused subject really pop. The trick here is to first to minimize depth of field by choosing a wide aperture, such as f/2.8 or f/4.5, and by choosing a longer focal length lens such as 50 mm or above. The problem you may find with wide angle lenses is that even at maximum apertures, depth of field can be too great to enable sufficient blurring of the subject. Next, if your main subject is in the background, you need to focus on something into the foreground to throw it out to focus. Conversely, if the main subject is in the foreground, focus on something behind it to throw it out of focus. If you have difficulty with your auto focus system locking on to unwanted subjects, switch to manual focusing.

Your other option is to defocus the entire image, an effect that can work superbly with people, plants and nude studies. You can use the same aperture and focal length settings as before but this time you may find it easier to which to manual focusing. Otherwise, you will have to auto focus on something outside the frame in order to blur out the entire frame, lock the focus, and then recompose.

Whether you blur the entire image or just part of it you’ll need to experiment a little to get the amount of blur just the right: too little and your image will just be slightly soft, too much and your subject will be unrecognizable. To reduce the degree of blur chose a smaller aperture and/or a wider focal length; to increase it chose a longer focal length and/or a smaller aperture. One other factor to bear in mind is that with all lenses depth of field is shallower when you focus on subjects close to the digital camera than it is when you focus on distant subjects.