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Length Formula:
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The length from image calculation uses the principles of perspective and optics to determine the actual size of an object based on its image size, distance from the camera, and the camera's focal length. This is particularly useful in photogrammetry, computer vision, and various measurement applications.
The calculator uses the formula:
Where:
Explanation: This formula is derived from similar triangles in perspective projection, where the ratio of image size to focal length equals the ratio of object size to distance.
Details: This calculation is essential in fields like computer vision for object measurement, photography for planning shots, forensic analysis for evidence measurement, and industrial inspection for quality control.
Tips: Enter the image length in pixels, distance in millimeters, and focal length in millimeters. All values must be positive numbers. For accurate results, ensure consistent units across all measurements.
Q1: Why is focal length important in this calculation?
A: Focal length determines the magnification of the lens, directly affecting how object size relates to image size.
Q2: Can I use different units for the inputs?
A: Yes, but all measurements must use the same units for consistent results. The calculator currently uses millimeters for distance and focal length.
Q3: How accurate is this calculation?
A: Accuracy depends on precise measurement of distance and focal length, as well as lens distortion characteristics. It works best with calibrated cameras.
Q4: Does this work for all camera types?
A: The formula works for ideal pinhole cameras. Real lenses may introduce distortion that affects accuracy, especially with wide-angle lenses.
Q5: Can I calculate distance instead of length?
A: Yes, the formula can be rearranged to calculate distance if you know the actual object size and image size.