"Bokeh" makes your footage look more film-like: a creamy-blurred background with a sharp, in-focus image in front of it. Derived from the Japanese word (boke) for a mental fog, it's best created by using a large sensor camera, like a Canon DSLR, combined with a fast lens. But there are plenty of other considerations: like how much space you have between your subject and the background, the f-stop settings on your camera, and the focal length of the lens you are using. So let's take a look at how to create this so-called "bokeh."
Finding Bokeh With Your Camera
For shallow depth-of-field:
1. Consider Your Spacing
Put as much space between your subject and the background as possible. 15 feet is a great start. It will throw the background out of focus and cause a nice smooth blur that gives the video a 3D feel.
2. Consider Your F-Stop
Grab a lens with a large maximum aperture, one that has a setting of f/2.8 or lower. f/1.8 or lower is even better. Your aperture settings will play a big factor in creating your depth-of-field. The lower the f-stop, the more shallow the depth-of-field, and the more "bokeh" your image gets. The higher the f-stop setting, the more everything will be in focus and therefore less "bokeh."
For example, try pointing your camera at a small light, such as a Christmas light, and go through all of your aperture settings from f/15 and "stop down" as low as your lens will allow. As the f-stop gets lower you should see the light become a smooth, round circle as it goes out of focus.
3. Consider Your Focal Length
Somewhere on your lens is a measurement that shows the focal length in millimeters. The higher the focal length (200 mm for example) the further away your lens will reach and the easier it will be to create shallow depth-of-field. A shorter focal length (something like 24 mm) will require you to put more distance between the subject and the background in order to get the background out of focus.
For more about interchangeable lenses, look at this awesome article.
And if you don't want to learn more about focal length, definitely don't click on this link.