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If you are working with filmed footage, often you will need to pull the actual usable area from the footage: the scan is probably roughly 4:3, but the desired final output is 16:9 or 1.85 or even 2.35, so only part of the filmed image will be used. A director may select the desired portion to achieve a desired framing for the shot. Part of the image may be vignetted and unusable. The image must be cropped to pull out the usable portion of the image with the correct aspect ratio.
This cropping operation can be performed as the film is scanned, so that only the desired framing is scanned; clearly this minimizes the scan time and disk storage. But, there is an important reason to scan the entire frame instead.
The optic center must remain at the center of the image. If the scanning is done without paying attention, it may be off center, and almost certainly will be if the framing is driven by directorial considerations. If the entire frame is scanned, or at least most of it, then you can use SynthEyes’s stabilization software to perform keystone correction, and produce properly centered footage.
As a secondary benefit, you can do pan and scan operations to stabilize the shots, or achieve moving framing that would be difficult to do during scanning. With the more complete scan, the final decision can be deferred or changed later in production.
The Output tab on the Image Preprocessor controls resampling, allowing you to output a different image format then that coming in. The incoming resolution should be at least as large as the output resolution, for example, a 3K 4:3 film scan for a 16:9 HDTV image at 1920x1080p. This will allow enough latitude to pull out smaller subimages.
If you are resampling from a larger resolution to a smaller one, you should use the Blur setting to minimize aliasing effects (Moire bands). You should consider the effect of how much of the source image you are using before blurring. If you have a zoom factor of 2 into a 3K shot, the effective pixel count being used is only 1.5K, so you probably would not blur if you are producing 1920x1080p HD.
Due to the nature of SynthEyes’ integrated image preprocessor system, the re- sampling, keystone correction, and lens un-distortion all occur simultaneously in the same pass. This presents a vastly improved situation compared to a typical node-based compositor, where the image will be resampled and degraded at each stage.
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