The Advanced Art of Stop-Motion Animation: Digital Cinematography: Part 2
If a subject you are shooting with a stationary camera moves while the shutter opens to take the picture, the result will be a blurred image of that subject. You may have seen this happen when taking pictures at a party or any other situation. For instance, your friend was talking when you took the picture or spun around quickly without realizing you were snapping the frame, and the result is that his head is all blurry. This is one example of unwanted motion blur in a picture, but in other cases there are aesthetic choices for deliberately using the technique. You may have seen images of cars zooming down a highway at night and becoming long streaks of light caused by the headlights moving across the frame. This is caused by the light moving in a consistent direction while the shutter is open for a longer shutter speed, typically a full second or more. A long shutter speed is typically the key to making this happen, and it’s important to remember to combine this with a low f-stop since light is entering the lens for a longer period of time. The effect is to artistically achieve a feeling of motion within one static image.
For Fabricated, Brett Foxwell employed an artistic application of motion blur for a certain scene. For the effect of a surreal flame that is encountered by his puppet character, a pleated copper sheet was mounted on a motor shaft spinning along its vertical axis. The motor would be turned on to spin in front of the camera shooting a 1-second exposure, which made the sheet appear blurry while the puppet was static and stayed in focus (Figure 4.16). Between frames, Brett progressively cut the sheet apart and tacked on curved pieces of brass foil, continually bending and twisting them to create additional movement (Figure 4.17).
Motion blur can also be added to a puppet character or object that is meant to be moving very quickly across the screen or as a method of making the animation appear smoother. If the individual frames from the animation are blurred, the shot has the potential for a closer resemblance to live-action photography, which will typically have blurred action if any motion being filmed is faster than the camera’s shutter. One simple method for achieving a blur effect on set is to place a sheet of glass onto the camera lens or directly in front of it, and then use Vaseline to smudge the place where the puppet is. K-Y can also be used since it is water based and easier to wipe off the glass. The smudging would need to be removed and re-applied for each frame as it follows the motion of the object. Using this method means your puppet or object still needs to be static, but the illusion of an unfocused blur is created by the glass effect. The alternative is to find a way to actually move the puppet while each frame is being taken. People have achieved this in various ways. Attaching invisible strings to the puppet and yanking on them while capturing is one method. Finding a way to vibrate the set is another. Whichever method is used, the trick to effective motion blur is finding a way for the blurring action itself to follow the path of action in which the puppet or object is moving. If an object is moving diagonally from left to right, for instance, the direction of the blur should appear to be trailing behind in that particular direction. Applying motion blur to a puppet can also be done through various post-production methods, which are covered in Chapter 9: Visual Effects.