In the lateral chromatic aberration formula CA = (dD)/v, what does the variable d denote?

• A. Distance from the optical center
• B. Power of the lens
• C. Abbe value
• D. CA value

Answer: (A)

The main idea here is that lateral chromatic aberration depends on how far you are from the optic axis. Different wavelengths are dispersed by the lens, causing a lateral shift that grows as you move away from the center of the lens.

In the formula CA = (dD)/v, the variable d represents the distance from the optical center (the lens center). As you measure color displacement farther from the center (larger d), the lateral chromatic aberration increases. The other factors, D and v, scale or translate that displacement, but they do not identify the positional variable itself. If you’re right at the center (d = 0), there’s essentially no lateral color shift.