Optical Calculators

Field of View Calculator

Predict how wide a patient's view will be through a magnifier, so you can choose the right lens size and coach them on the optimal holding distance. Enter the lens power, lens diameter, pupil size and lens-to-eye distance.

Stronger magnification always shrinks the field of view. Hold the magnifier too far away, or choose a lens that's too small, and the patient may see only a few letters at a time. This calculator traces light through the magnifier and the pupil to show where that limit falls.

Inputs:

  • Lens power (D)
  • Lens diameter (mm)
  • Iris diameter (mm): the pupil, which acts as the viewing window.
  • Lens to iris distance (mm): moving the magnifier closer widens the view.

Results, in degrees:

  • Field of uniform illumination: the fully bright center.
  • Conventional field of view: the comfortable reading zone, at least half illuminated.
  • Total field of view: the outer edge, where the image fades out.

For a quick answer in centimeters instead of degrees, use the Field of View (Simplified) Calculator.

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