User manual

Functional Descriptions 381

9.8 Supported File Formats

A cine file, or movie, may contain hundreds of pictures, while an image file contains a single picture

extracted from a cine file. Vision Research recommends that you use the Cine RAW format, unless

there is a real need to use one of the other formats. Following are brief descriptions of the advantages

and disadvantages of the various supported file formats.

IMPORTANT DEFINITIONS

Color interpolation (Demosaicing)

Color images usually contain three color components for each pixel (Red, Green, Blue). In order to

produce color images, digital cameras should be able to measure color levels for all three

components in each pixel of the image. Hence, three different sensors would be required.

Since this approach is expensive and very complicated to implement, most cameras use only one

sensor plus a Color Filter Array (CFA). The CFA is a grid that selectively filters the light by

wavelength range. The image below contains such a filter, called the Bayer CFA.

Bayer Color Filter Array

Thus, the camera sensor will produce an array on values with one value per pixel. Each value

represents a specific color level (red, green or blue). Such an image is usually called uniterpolated

or RAW image.

In order to obtain a full color image from the RAW image, a special processing is required, called

color interpolation or demosaicing. Analyzing each pixel and its neighbors, a color interpolation

algorithm basically reconstructs the missing color components and produces the desired color

image.

Raw

The term “RAW” generally refers to something unprocessed, unrefined. In digital video and digital

photography, there are two contexts RAW is most often used:

· When referring to how data is stored in an image file.

In this context, a RAW file generally stores an image as a stream of bytes without using any

compression or special technique. By default, the file contains no additional data. However,

some RAW files may support adding a header with minimal information such as image size or

bit depth. Vision Research .RAW format is an example for this category.

· When referring to what kind of data is stored in an image file.

A RAW file format may also refer to a file format that contains the original, unprocessed data

from the image sensor of a digital camera. A RAW file is not immediately ready for use, but it

contains all additional information for processing it and further using the captured image. DNG

is an example of a RAW file format.