Apple Shake 4 - Manual (Page 209)

Chapter 6 Importing Video and Anamorphic Film 209
The result of this expression is that if videoType is not zero (in other words, videoType is
set to PAL), videoGamma is set to 2.8. If videoType is set to 1, videoGamma is set to 2.2.
For more information about how expressions work, see Chapter 30, “ Installing and
Creating Macros ,” on page 905.
About Aspect Ratios and Nonsquare Pixels
Shake has several controls in the Globals tab to help you work with nonsquare pixel
images. These images are typically video images, or anamorphic film images. Different
controls are used for the two types, due to the nature of the data that is manipulated.
• In order to avoid mixing up each frame’s field information, nonsquare pixel distortion
is corrected by extending the image horizontally (in the X direction) and not
vertically.
• For anamorphic film plates, because the primary concern is the amount of data that
is calculated, the image is vertically squeezed. This has the added benefit of reducing
frame size of the image, which lets Shake process your script faster. In the case of
CinemaScope, this not only corrects the anamorphic distortion, but also speeds
Shake’s interactivity by a factor of two.
When you correct nonsquare pixel images, you need to know the aspect ratio of the
image in order to see the transformations and corrections without distortion. For this
discussion of different aspect ratios, film anamorphic plates are used to illustrate how
to work with such frames. Although this solution applies specifically to film plates, the
principles and problems are similar for anamorphic and non-anamorphic video,
although the aspect ratios vary depending on the video format.
What is Anamorphic Video?
Anamorphic processes such as CinemaScope create film frames that allow for an
extremely wide-screen aspect ratio when projected. This is accomplished by filming
with a special lens that horizontally squeezes the incoming image by half horizontally,
in order to fit twice the image into a conventional frame of film.
When viewed without correction of any kind, each frame appears very thin on the
physical negative. When the film is projected in the theater, a reverse lens is used to
expand the image by 2:1 horizontally, which returns the image to its original (wide)
format. It is important to understand that the recorded image is only widescreen in two
places—in front of the lens when filming, and on the projection screen. During the
postproduction process, you are usually working with the squeezed image.