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Digital Reregistration Of Separations

To Form Color Images

Andrew Bonello (MEng)

Cinesite, Los Angeles

Abstract: A technique is introduced for recombining scanned film separations in an automated digital framework. Manual alternatives are labor-intensive and error-prone. By making use of image deformations and channel matching within an efficient sampling framework, the technique robustly reregisters film-resolution scans from Academy to Vista Vision format. Automated reregistration is demonstrated in action for the movie “Williamsburg: The Story Of A Patriot”.

Section 1 – Introduction

Film masters for older films exist in several formats. In some cases, work starts with separations. The process begins with three separate strips of film, all containing image data for the same piece of footage. These three pieces of film are created by optically exposing a color negative CMY film element with red, green and blue light respectively.

A full color image is obtained by optically recombining the information from these three strips of film on top of one another. Thus, the Cyan, Magenta and Yellow information from the original color negative is converted into the Red, Green and Blue channels of a positive color image.

The main contribution of this paper is to describe a technique for digitally reregistering separations in an automated framework. The document is organized as follows. In Section 2, a typical pipeline used for manual reregistration in a post-production environment is described. Section 3 introduces the new automated technique at a high level. In Section 4, details are given about the implementation of the new technique. Section 5 concludes by describing the overall function of the tool, as well as the different sources of input images which can be handled.

Section 2 – Manual Reregistration

The process of optically creating and reregistering film footage from separations can introduce unpleasant color aberrations in the image (see Figure 1). These are usually the result of poor pin-registration and film shrinkage. Such color fringes are referred to as misregistration in the image.

[Figure 1: Pin misregistration and film shrinkage between layers cause unpleasant color fringes in the resulting image]

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