bacsa Posted July 14, 2003 Share Posted July 14, 2003 I just tested my dynax 5 for the accuracy of shutter speed. Hereby i gladly share the results. <p>Method: <br>no lens on camera body, low-power HeNe laboratory laser, focussed on amplified silicon detector, 100MHz HP storage oscilloscope. Recording the pulse-shape signal on the scope that shows up on the monitor while the shutter is open. Measuring FWHM of this trapezoidal pulse with the scope's cursors. <p>The error of the measurements in the case of fast speeds is slightly larger, due to the ill-defined rising and falling edge of the pulse. These edges seem to be the same for all shutter speeds in absolute values: ~50 microseconds, and are related to the movement speed of the certain shutter leafs. However, at the fast end, since the whole open-shutter time is shorter, the relative error becomes larger. <br>The time while the shutter is open and light can hit the film <i>in one certain point</i> (the so-called shutter speed)is measurable by measuring the flat top of the pulse trapezoids. <p>Results for the shutter speed: <br>___Set speed ______________Measured speed_____relative difference <br>_____ 30s________________________34.0s___________13.0%______ <br>_____ 20s________________________22.5s___________12.5%______ <br>_____ 15s________________________16.3s____________8.7%______ <br>_____ 10s________________________11.0s___________10.0%______ <br>______ 8s_________________________8.5s____________6.3%______ <br>______ 4s_________________________4.1s____________2.5%______ <br>______ 2s_________________________2.0s______________0%_______ <br>[between 2s, and1/500s, unmeasurably close values.] <br>_____1/500s_____________________1/520s____________4.0%______ <br>____1/1000s____________________1/1040s____________4.0%______ <br>____1/2000s____________________1/2090s____________4.5%______ <br>____1/4000s____________________1/4040s____________1.0%______ <p>As expected, the only real deviations from the set values show up at slow shutter speeds - however, I'm quite happy to see that the largest error is around 1/10th of an f-stop. <p> I plan to do more tests, such as shutter lag time, frames/second speed, and diafragma accuracy for the lenses I own. Any ideas/comments welcome. Link to comment Share on other sites More sharing options...
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