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Lens calculator - Calculating the focal length
The focal length f´ virtually serves to calculate the required lens and is thus the most important specification to characterise an (entocentric) normal lens.
f' = g / (G/B + 1)
The theoretic value of the focal length calculation serves to find the best suitable optics. Typical increments of focal lengths for C-mount lenses are e.g. (1.8, 2.8, 4, 6,) 8, 12, 16, 25, 35, 50 and 75 mm.
Note: Even when using the drop-down lists own values can be entered. Please use the first entry "user def."!