Motion About image sequences
Numbered image sequences store video clips as individual still image files. Each image file has a number in the filename that indicates where it fits into the sequence. In a film clip that’s been digitally scanned, each file represents a single frame. In a video clip that’s been converted to an image sequence, each file contains both fields of a single video frame, with the upper and lower lines of the image saved together.
Image sequences use the same variety of file formats as still image files. Some of the most popular formats for saving image sequences include SGI, BMP, JPEG, TIFF, and TGA. Like still image formats, many of these image sequence formats support alpha channels, which are used by Motion.
Because image sequences have been around for so long, they remain the lowest-common-denominator file format for exchanging video across editing and compositing applications. Although QuickTime is increasingly used to exchange video clips between platforms, image sequences are still used, especially in film compositing.
As with QuickTime video clips, you can mix image sequences of different formats, using different frame sizes, pixel aspect ratios, frame rates, and interlacing.
Important: Any imported image sequence must contain three or more digits of padding—for example, “imagename.0001.tif.”
Collapse image sequences
The “Show image sequences as collapsed” button at the bottom of the File Browser lets you display image sequences as a single object, rather than as the collection of files on your disk. 
Note: You can turn this feature off for numbered image files that aren’t used as an image sequence. For example, pictures taken with digital cameras often have numbered filenames that can be mistaken for an image sequence.