Description
Compute exact geometric angular extent of a centered planar target from compatible supplied dimensions.
Optical calculations distinguish lens power in diopters, prism notation, angular axes, geometric distances, and visual-acuity reporting scales. Sign conventions and length units are especially important when a formula combines power with decentration or vertex distance. A supplied model term is separate from a validated visual test or prescription.
Compute exact geometric angular extent of a centered planar target from compatible supplied dimensions.
When to use this tool
Use Near Target Angular Size when you need this explicit optical, chart, frame, axis, or reference conversion with compatible supplied units.
How to use the tool and how it works
- Enter targetSize, viewingDistance. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read angleRadians. Use the output convention below.
For nonnegative targetSize and positive viewingDistance return angleRadians=2*atan2(targetSize/2,viewingDistance).1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| targetSize | Target Size | Required. Finite number; minimum 0. |
| viewingDistance | Viewing Distance | Required. Finite number; strictly above 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| angleRadians | Full angular width in radians, not a half angle. | Required. Finite number. |
{
"input": {
"targetSize": 2,
"viewingDistance": 1
},
"output": {
"angleRadians": 1.5707963267948966
}
}Limitations and assumptions
- Target size and distance need one length unit and the target is assumed centered perpendicular to the viewing axis. The result is full angular width, not an acuity score or verification of a clinical stimulus.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use the appropriate complete optical or measurement model when a scalar term is insufficient. Verify power, axis, length, notation, and reference conventions before applying the result within a broader assessment.
References
Similar or alternative tools
- Visual Angle Stimulus Size
Return the exact centered planar stimulus angular width from supplied compatible dimensions, without an acuity score.
- Eye Tracker Screen Gaze Angle Term
Flat-screen geometric gaze offsets from explicitly calibrated coordinates and viewing distance, not an eye-tracker calibration or diagnosis.