For the last 2 months, I have been enjoying a new digital camera, a Nikon P500. This is a hybrid camera, incorporating features of a full size digital SLR on a much smaller platform. Most remarkable is the 32x optical zoom which allows much easier wildlife photography, particularly wild birds. It is almost more zoom than I can handle.
One problem with the camera is interesting from the perspective of system testing. The camera battery can be recharged by removing the battery and placing it in a charger, or you can option the camera to charge the battery through the power feed on a USB interface. Since the charger was not included in the camera kit, the USB mode seems to be the manufacturer’s preferred mode. When you connect the camera to a computer using the USB cord, the on/off light turns green, then flashing orange, to indicate charging state... after a few minutes or hours, the on/off light returns to steady green, indicating a full charge. 30 minutes later, the camera turns itself off. While the camera is charging, you can transfer photographs and videos to your computer and perform other functions.
The problem occurs when you disconnect the camera from the computer. If you press the on/off button first and then disconnect the USB cable, the camera turns off the port and holds its charge. If you disconnect the USB cable first, the camera does not power down the port and after a couple of hours will completely discharge the battery. This has happened to me on several occasions. You expect to have a full charge, however, all you have is a dead camera. Any photographs for that session are impossible. The correct procedure is documented in a notes section, however, there is no indication in the trouble shooting section about the danger of changing the sequence of disconnecting the camera.
If you think about feature verification testing, the camera works perfectly as specified, and neither software testing nor hardware testing would have found this problem. Only usability testing that explores all the different things users might naturally do wrong would have uncovered this problem. The other option is to let the customers discover the problem. Until I figured out what was wrong and how to fix it, I was ready to return the camera to the store. Once discovered, documentation should be improved to help shoot the trouble and change user behavior, however, the right answer is to change the software control so that the sequence of button or USB cord disconnect first doesn’t create a discharged camera.
I’m reminded of a problem that usability testing identified at Ameritech in the early 1990’s. At that time, Ameritech had deployed cross connects and STPs from the same manufacturer. Sometimes, they were located near each other in central offices. It turned out that cards from one machine could be inserted into slots on the other machine with disastrous effect. There were no mechanical lockouts that prevented this card swapping from happening if the operator got confused. The result of the usability testing was a requirement to prevent this swap mechanically.
What’s your experience with usability testing? Have you had a similar experience to the P500 camera discharge problem?
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