Rack Focus Definition:
Racking focus is the process of switching the focal point from one subject/object in a frame to another subject/object that is closer or farther from the camera, whereby one subject is sharp and clear while another part of the frame is blurry (out of focus). The camera itself does not generally move during the focal change.
By keeping one subject in focus and the rest of the scene out of focus, the cinematographer can draw the audience’s attention to the subject in focus. If the cinematographer wants to draw the audiences attention to another subject, s/he can then rack focus and place the focus on another subject, leaving the original subject out of focus/blurry. The rack focus shot is commonly used when two people are talking. The focus is switched between the two speakers as each subject speaks.
Usually this involves focusing from a subject in the foreground to a subject in the background and vice versa. If you watch Korean soap operas like I do, they often use this technique. For example, say Fabio in the foreground is talking candidly on the phone to his secret lover, when in the background we rack focus on to Sally, Fabio’s girlfriend, who has just entered the room and gasp has just overheard and learns of Fabio’s infidelity!
Rack Focus Example:
Racking Focusing Techniques With a DSLR:
For such a simple process of interchanging focus points, there are many different ways to rack focus. There’s even an entire occupation in film production (called focus pullers) dedicated solely to achieving focus in films.
Generally, you’ll want to have your different subjects spaced a distance away from each other. That way you can effectively keep one subject in focus while blurring out the other subject. If the subjects are too close together then it’ll be harder to keep only one subject in focus. Cameras lenses have a plane of focus, meaning that subjects that are all at an equal distance away from the camera will either all be in focus or all out of focus at the same time. Thereby varying the distance of the subjects from the camera will effectively put them on different focus planes.
Next, you’ll want to use a lower aperture to produce a shallow depth of field, meaning only a thin plane of the frame will be in focus.
And now we will focus (pun intended) on a few different techniques:
- Technique 1: Manual Focus
If you’re familiar with your lens and DSLR then changing focus from one subject to another should be a simple task.
When using a DSLR, you’ll most likely need two hands to rack focus. One hand to hold the camera, and the second hand to adjust the focus on the lens. This will cause the camera to shake. To make things easier and to produce a better quality video, you’ll want to lock your camera down on a tripod, thus freeing up one hand and keeping your camera stable.
The ideal for rack focusing is to find your focus points before filming and then make sure your subjects don’t move. From what I understand, there are systems that have follow focus with hard stops so you can easily know how many “clicks” to turn your focus to get from focus point 1 to focus point 2. However, I’m using a Canon lens setup which spins to infinity and has no hard stops. So while recording and switching focus points, it may be difficult to achieve critical focus at your end focus points (rack focus subjects), so a cheap DIY hack you can try is the post its and jar opener method outlined here.In summary you use post it notes to mark your end focus points on the camera and rack between the two (or more) points.
For Canon cameras, users have the option of installing Magic Lantern, which is a third party firmware add on that offers you the ability to rack focus accurately with a push of a button.Tip: This is just one of the features Magic Lantern adds. I have a whole Magic Lantern series of articles dedicated to the wonders that Magic Lantern can provide.
- Technique 3: Specialized focus accessories and rigs
For the professional film makers, achieving tack sharp focus is critical and so they may choose to invest in accessories and rigs designed specifically for this task. One interesting gadget is the Focus Shifter which makes achieving focus easier by adding hard stops to your lens. Another option is the Fotasy Pro Grade Quick Release Follow Focus Rig for HDSLRs as shown below:
Whatever technique you use, integrating a few rack focus shots is sure to enhance the creativity of your project. But like all the other camera tricks and techniques, just be sure you don’t over do it.