1. Shake is Distracting
When watching video, people tend to fixate on points of interest in the scene and switch between them. If the viewer cannot focus on a point because shake is moving the camera either randomly or in a difficult to predict way then the footage becomes difficult to watch. If the shake is cyclic or fluid the viewer's eyes are constantly working to track the object and will get tired quickly. The viewer may look away or give up and wait for the next scene to see if things improve.
Smooth and deliberate (predictable) camera motion has the effect of bringing the motion of the action into focus. Any action that has skill, e.g. sports, craftsmanship, etc. can be unclear if the camera motion is not stable.
2. Stable Video Looks More Professional
Professionals use several pieces of equipment to obtain stable video shots. These include tripods, dollies (moving platforms on wheels usually on a track), sliders (metal panel with rails that mounts on a tripod), jibs (a swing arm with counterbalance weight that attaches to a heavy duty tripod), cranes and body mounted harnesses with counterbalance weights. Movies are made with this kit for a reason - it looks better.
Not everyone has access to the crew and budget to use all those tools; besides, there are situations where handheld video can give a more natural look, get closer to the subject or fit into a scene where dolly track or a crane would be inpractical. Using a handheld camera has advantages, but the video must be stable to be considered good quality.
3. Zoomed In and Long Lens Shots
Handheld video naturally has some shake, it's unavoidable; you could be tired, jostled, walking on uneven ground, etc. When zooming in, shake is exaggerated regardless of whether you are moving. A small deviation from the point the camera is aimed at suddenly becomes huge.
4. Live Action is Unpredictable
The unpredictability is what makes live action so interesting. Sometimes a unique, one-off event occurs, such as an accident or fluke. Your camera work can't anticipate every future event; even when intricately planned, things don't work out how you expected them to.
- Stunts can go awry
- Members of the public can wander into the background
- Improv scenes can surprise or shock
- The cameraman can forget the plan of action when the shot is long or complex
5. Difficult to Re-shoot / Cost
Reshooting a scene is always difficult and adds more expense. If you don't have the budget or you can't go back to do the shot again then you can't reshoot. The shot is fine except for shake. Why not fix it in post ? You're editing the shots, color grading, etc. so why not the motion ?
MotionBend is a video stabilization and motion editing application for Mac. It produces good quality results and is within reach of most budgets so you can enjoy the flexibility of a handheld camera and stable video.