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The source uses the geometric field of view, twice arctangent of sensor dimension divided by twice physical focal length. For its APS-C dimensions twenty-three point five by fifteen point six millimeters, six hundred millimeters gives a horizontal field of about two point two four four degrees and vertical field one point four nine zero degrees. At twelve hundred millimeters, horizontal field is about one point one two two degrees. The two view wedges here share a five-hundred-pixel projected horizontal distance and their opening angles are the actual horizontal fields, exaggerated only by the diagram scale announced as twenty times angle to make them readable. Equivalent focal length is a crop-based framing comparison: six hundred times one point five equals nine hundred millimeters. It does not turn the physical lens into a nine-hundred-millimeter lens, change its f-number, or establish telescope magnification without an eyepiece. The source angular sampling is two hundred six point two six five times pixel pitch in micrometers divided by physical focal length in millimeters. With pixel pitch four point three, six hundred millimeters gives one point four seven eight arcseconds per pixel; twelve hundred gives point seven three nine. The sampling bars share two hundred pixels per arcsecond per pixel. Smaller sampling angle is not a guarantee of sharper photographs. Its ideal green-light Airy diameter is one point three four two times f-number, in micrometers. At f five point six that diameter is seven point five one five micrometers; at f eleven point two it is fifteen point zero three zero. The disk diameters here share ten pixels per micrometer. Sampling bars and diffraction disks each have their own stated units. Focus, atmosphere, aberrations, motion and image processing are not solved by either scalar. For six hundred millimeters, f five point six and pixel pitch four point three, the source heuristic limit is sixteen point nine times f-number plus point zero nine times physical focal length plus thirteen point seven times pixel pitch, all divided by physical focal length. This gives about point three four six seconds. Its five-hundred rule instead divides five hundred by the rounded equivalent focal length of nine hundred and gives about point five five six seconds. These two bars share seven hundred pixels per second; their unequal lengths show the source rules disagree. Neither is a measured exposure guarantee. Wildlife suggested shutters are fixed target defaults, and celestial declination, guiding and acceptable blur thresholds are not inputs. Target coverage divides angular subject size by field angle using a linear approximation and clips at one hundred percent. Tiny canvas targets have minimum graphic sizes, so illustrations are not pixel-exact photographs. The loaded Two library is not the optical solver: source formulas and a native canvas create the actual report.