Digital Blending

Macro Economic Telecine System (METS)

The PIC processor made experimentation with digital blending possible. Digital blending requires the capture of two images of the same film frame taken with different exposures, typically with about 3 f stops equivalent between them. I used a change of the illumination level to capture the two images for each film frame. The PIC is used to switch between the two preset levels of constant current fed to the LED light source. Low LED current is used when setting the camera exposure, using the zebra pattern indicator function, to avoid clipping of highlights for a scene/film to preserve detail in the highlights and then the exposure is locked. The detail in the shadows may be lost in this first exposure. High LED current is used for the second exposure of the film frame that should improve the detail in the shadows but will clip the highlights. Since a clipped highlight cannot be greater than 255,255,255 in 8 bit RGB or a blocked shadow less than 0,0,0 when the two images are blended [(Low + High)/2] detail should be present in both highlights and shadows of the blended image. Capturing two images for each film frame to be used in digital blending is rarely justifiable for normal captures because of the resultant loss in speed of capture.

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