MATLAB source: efl_calc.zip.
Focal length can be determined from a series of images of a target board at varying distances between the camera and the target. The camera used here is a Fugifilm Finepix 6900 with zoom lens set at its power-on value.
Our analysis consists of the following steps.
ginputis called to solicit user input. See the MATLAB code img_meas.m. The results are stored in
imgdata.mat. The results are displayed graphically with img_array_data.m.
polyfit). Determine the focal length from the slope of this line. See the results in efl_calc.m. The plot is also shown below
The desired parameter value is f = 2542.3 pixels
Distances were measured in cm. For comparison, 200 inches (above) corresponds to about 500 cm
Maintained by John Loomis, last updated 2 June 2012