Lens Focal Length Calculator
Ideal thin lens signed focal length from actual signed object/image distances, nonzero denominators, real/virtual sign convention stated externally. Actual independently established compatible SI units/model context; conditional arithmetic, not code compliance, engineering design or safe operation approval.
Description
Thin-lens focal length can be calculated from signed object and image distances under a consistent optical convention.
Thin-lens focal length can be calculated from signed object and image distances under a consistent optical convention.1
This tool evaluates the finite reciprocal relation without identifying the real or virtual branch for the caller.
When to use Lens Focal Length Calculator
Use this tool to evaluate the finite reciprocal relation without identifying the real or virtual branch for the caller.
How to use Lens Focal Length Calculator and how it works
- Prepare actualObjectDistanceMeters, actualImageDistanceMeters, with the units, conventions and assumptions below.
- Enter the required fields and run Lens Focal Length Calculator.
- Read result.value using the output definitions below.
- Correct any rejected inputs and rerun; interpret the result within the stated model and its assumptions.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| actualObjectDistanceMeters | Actual Object Distance Meters. Use the units and matching context stated in the calculation below. | number | Required; finite; other constraints below |
| actualImageDistanceMeters | Actual Image Distance Meters. Use the units and matching context stated in the calculation below. | number | Required; finite; other constraints below |
Supply finite nonzero signed object and image distances in matching length units. Require their reciprocal sum to be nonzero and return its reciprocal as signed thin-lens focal length. The tool does not determine the optical sign convention or handle an infinite focal length.
focalLength=1/(1/objectDistance+1/imageDistance) Apply the input ordering, units and branch conditions stated above.
| Output field | Meaning | Value type |
|---|---|---|
| result | Object containing the calculated or selected fields below. | object |
| result.value | Signed thin-lens focal length in meters. | number |
{
"input": {
"actualObjectDistanceMeters": 2,
"actualImageDistanceMeters": 1
},
"output": {
"result": {
"value": 0.6666666666666666
}
}
}Limitations and assumptions
The calculation uses the supplied observations and model inputs. It does not collect measurements, select a reference population or coefficient, or establish that the model applies to the actual case. The stated branch conditions and output units remain part of the result.
All fields require explicit values. Unexpected fields, wrong types, nonfinite numbers and sparse arrays are rejected. Alignment, bounds and supported-token rules are explained above; extremely large inputs or nonfinite results can also fail. Input errors differ from successful false comparisons, unavailable-domain flags and empty match lists.
Alternative or Complementary methods
Use Keystone Correction Angle Calculator for a complementary operation: A projected trapezoid's side angle can be calculated from its measured top and bottom widths and height.
Use Optical Magnification Calculator for a complementary operation: Thin-lens transverse magnification has a signed distance-ratio convention.
References
-
Lens Focal Length Calculator — tool.io
Similar or alternative tools
- Keystone Correction Angle Calculator
A projected trapezoid's side angle can be calculated from its measured top and bottom widths and height.
- Optical Magnification Calculator
Thin-lens transverse magnification has a signed distance-ratio convention.