Image Processing Reference
In-Depth Information
Figure 4-10 9.5mm Sprocket hole ghosting.
Note that the sprocket holes interfere with the picture. The cameras would often
overscan the image area, and the aperture in the projector gate was made somewhat
smaller than the camera gate aperture so as to crop the projected image. This also helped
to hide the gate weave in the camera. The actual size of images on 8mm film is quite vari-
able, and a casual search of the Web reveals a variety of different sizes and specifications.
The values quoted here are approximate. The make and model of the camera the film was
exposed in will determine the actual image dimensions on the emulsion.
If you are digitally scanning the film, it is a good idea to extract a slightly larger
image area than if you project the movie and film the result with a video camera. You will
also get a better-quality image that will be more stable.
Super 8mm
Super 8mm superseded the standard 8mm format in the 1970s and provided a larger
image size. It also had the advantage that the unexposed film was delivered in a single 50-
foot reel of 8mm stock and was mounted inside a cartridge. This made loading the cam-
era much easier and less prone to fogging the already exposed film.
Figure 4-12 illustrates how this format is different from the standard 8mm layout.
Note, for example, that the sprocket holes are oriented so the long axis is aligned with the
film. This allows a little extra room for an enlarged picture area. The frame sizes are big-
ger and the film would run to a slightly shorter playback time when projected.
Digitally scanned image sizes for this format would yield a raster that is almost the
same as a standard-definition TV picture in the USA at 633
460 pixels. Grain size is still
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