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The aperture map and obstacle map must have the same resolution. Your render and the maps used do not always need to have the same resolution, but the more similar they are in resolution, the less diffraction distortion you will get. The aperture map should be black with white specifying the shape and size of the aperture. The obstacle map should be white with black areas specifying dirt or scratches on the lens surface.
Some of the aperture maps included in the Maxwell installation
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