Focal distance and lens

The size of the WD and the view angle are determined by the focal distance and the CCD size. When NOT using a closeup ring, the following proportional expression can be applied.
WD : View angle = Focal distance : CCD size

When the focal length is 16 mm (0.63”) and the CCD size
is 3.6 mm (0.14”), WD should be 200 mm (7.87”) to make
the view angle at 45 mm (1.77”).
WD = 16 x 45 / 3.6 = 200 mm (7.87")

The graph on the left (visual field graph) shows the relationship between the focal distance, the working distance (WD), and the visual field. A suitable lens can be determined based on the intersection of WD and visual field. If an object is placed at a distance shorter than the minimum focal distance of the lens, attach a close up ring or spacer for a close shot. The solid lines between the dots in the visual field graph indicate the size of the close up ring.

When mounting a closeup ring of 50 mm (1.97") on a 50 mm (1.97")
lens, you can capture an image with a view of 3 mm (0.12") at WD =
90 mm (3.54"). (Intersection of red lines)