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How to Use Type 120 Targets:
Place the Type 120 film strip or slide into a film holder before starting the digitizing session. The strip width is 61 mm. Select between 6x7 or 6x9 images. For panoramic shots, you may use both frames. Capture images and review them on a computer screen to ensure:
Critical focus is achieved. This means that the center of the image, edges, and corners are equally sharp, resolving the same Group and Element as in all USAF 1951 patterns across the frame. The Siemens stars should be equally sharp, and the individual strokes in the targets should be well-defined with clearly defined edges. The fine raster, which is very uniform across the frame, helps ensure uniform sharpness.
Full alignment between the film holder and the camera is attained. This ensures that all elements of the target come into focus simultaneously, with no geometric issues, and all right angles remain accurate.
The optimal F-stop is dialed in for maximum sharpness across the frame. Typically, the best sharpness can be attained at a very specific F-stop, such as 5.6 ½ for the APO Rodagon. Deviation from this optimal value can lead to a deterioration in image quality.
Correct framing is established. Depending on the desired coverage area, the framing should be set to cover the frame. Typical borderless coverage is 56x70 mm for a 6x7 frame and 56x84 mm for a 6x9 frame. Various markers inside the frame make framing easy.
These targets are designed to assist with adjustments if any of the above points become problematic.
The absolute resolution of Type 120 and 4x5" targets is 43 line pairs per mm.
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