Discussing Measuring Flash Duration

Posted on Feb 6, 2014

Here is simple method that you can try. It might NOT be as accurate as scientific professional tools, but seems more accurate than some of the manufacturers. Wire the resistor in parallel with the photodiode to reduce saturation effect. Normally, wire the positive terminal of the photodiode to the sleeve and the negative terminal to the tip. Some sound card requires the other way around. The software

Discussing Measuring Flash Duration
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used in this thread is a free software named Audacity. I think it has PC and Mac version. Please google it because I don`t want to sound like their sales rep. Plug the hardware you made into the microphone port, if you have multiple sound cards, select the right one. Important note, set the sampling rate to the highest allowed by your hardware so it is more accurate, particularly when capturing 1/128 power level. The above capture is for YN560 first generation at 1/1 power level. As you can see, the curve starts at 28 samples and end at 560 smaples. At 96000 sample rate, this is about (560 - 28) / 96000 = 5. 54ms. This number is a bit large, probably caused by the 1k ohms resistor - it too large and could not dissipate the energy by the photodiode fast enough. The bottom line is, this method might not give you absolute result, but it gives you reasonable close number given its crudity. But if you are comparing flash durations with another brand, since you are using same setup, it will give you relative numbers to compare. Key point of doing comparisions is to keep everything securely positioned, same distance, and point the flash head on to the sensor at about 1 meter distance. Thanks! Interesting approach. I love the idea of converting to an audio signal and using Audacity to measure it. I`m hoping I`ll be able to record TTL flash control pulses this way. Question: I`ve tried doing something similar using the same type of...

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