Camera Lens Focal Length, Field of View and Working Distance

To choose a camera lens, specify the scene width and height you need to capture at the intended distance, then match that requirement to the active sensor area and image mode. Confirm the resulting coverage on the assembled camera before approving a configuration.

This guide develops a first-pass optical requirement and a practical coverage test. Use the exact module and lens documentation to confirm the proposed configuration.

Define the coverage in physical units

Start with a drawing of the scene. Mark the camera position, the closest and farthest object positions, and the region that must remain visible. Give horizontal and vertical coverage in millimeters or meters at those positions.

Include installation tolerances in that drawing. For example, an inspection project might need a 300 millimeter-wide object to remain in view while its center moves 20 millimeters in either direction. That hypothetical requirement calls for at least 340 millimeters of horizontal coverage before any additional installation allowance.

Write down the smallest feature that the application must resolve. Coverage and usable feature detail should each have their own acceptance criterion.

Match the field-of-view definition to the sensor

Field of view can describe an angular extent or a physical scene area. For a given active sensor size, focal length determines the approximate angular coverage of a conventional lens. Edmund Optics gives the first-order relationship for angular field of view as 2 × arctan(sensor dimension ÷ (2 × focal length)). Use matching horizontal, vertical, or diagonal dimensions. Focal length and field of view

Ask which active image area and sensor mode a quoted angle describes. Request a corresponding example image or coverage drawing for the proposed lens assembly. Include any intended image crop in the requirement sheet.

Work through a first-pass estimate

Consider a hypothetical rectilinear camera with an active sensor width of 4.8 millimeters and a focal length of 8 millimeters. The angular relationship above gives approximately 33.4 degrees horizontally.

Under a simple pinhole approximation, scene width is approximately distance × active sensor width ÷ focal length. At a distance of 500 millimeters from the model's projection center, the example gives approximately 300 millimeters of horizontal coverage. If the output has 1,920 horizontal pixels across that width, the average sampling is approximately 6.4 pixels per millimeter. Edmund Optics provides related first-order imaging relationships and their approximation limits. Imaging-system parameter calculations

These calculated values provide a starting point for the hypothetical configuration. Real close-focus geometry and lens behavior require the manufacturer's model and a physical test. Ask how the supplier defines working distance on the mechanical drawing so the installation can use the same reference point.

Check geometry across the image

Lens distortion changes the mapping between object position and image position across the field. Edmund Optics explains that this geometric effect can be characterized and mapped. Include the planned correction settings when evaluating coverage and measurements. Lens distortion

Place a target at the application plane and inspect both the center and edges. Save the original image, any processed image, and the processing settings. If the application measures dimensions, compare known target positions with reported positions throughout the required region.

For paired cameras, check the common usable scene at the actual operating distance. Review the stereo calibration guide when the application depends on matching features between the two views.

Verify focus and usable detail

Define the range of object distances your project needs, then evaluate the required features at each distance. Use a target with suitable patterns and dimensions. Edmund Optics describes how resolution, contrast, distortion, and other image-quality properties can require different test targets. Choosing a test target

For each capture, save the target position, focus setting, lighting, exposure, output dimensions, and processing configuration. Check the actual application result, such as successful feature detection or an acceptable dimensional error. Record any region where performance falls outside the project criteria.

If the host converts or crops the captured image, include that processing in the test. Our RAW, YUV and ISP guide helps document the image path reaching the application.

Prepare the optical requirement sheet

Use one sheet for the proposed lens and image mode so the supplier and application team can review the same geometry.

For our dual-lens camera module, ask us to confirm the lens and field-of-view information for the configuration under consideration. Add the host platform and quantity to your requirement sheet.

Use the integration checklist for connector and software checks. Send your project details with the scene drawing and required distance range so the optical requirements can be reviewed before ordering.