Does anyone use the iPhone TimeStamp Camera app to determine the accuracy of their quartz\HAQ watches? If you pay $4.99 for the premium app, it will provide video and photo timestamps that are to the thousandth of second (I’m fine with the hundredths-of-second precision)! This is what I use to determine the accuracy of my mechanical, quartz, and digital quartz watches.
I believe the reference time on the iPhone is pretty darn good. In fact, when I use the Emerald app, it seems like it’s almost always within 50 milliseconds, and often it’s within 10 of NIST. For analog watches (especially mechanicals), I just use a photo, but for digitals, I use the video and find the precise moment when the second forms solid numbers on the LCD.
I don’t think there is an easier or quicker way to get the job done. Who else uses this app?