Early adopters of Apple Watch models have discovered a hitherto unknown bug: the sensors on the underside of a Watch can become confused if the owner happens to be heavily tattooed in the wrist area.
Users have begun to complain on social media sites online that certain functions fail to work properly when worn adjacent to tattooed skin, under the hashtag #tattoogate.
Issues being reported include a Watch's locking mechanism failing to work on decorated skin; incoming message alert signals not being triggered reliably and heart-rate readings being markedly different between areas of plain and decorated skin. Some users also reported that their Watch repeatedly asked for the unlock activation/passcode, presumably due to confusion caused by the tattoo ink, as non-inked wrists were fine.
An Apple support article on the company's web site states that Watch uses green LED lights and light-sensitive photodiodes to detect the amount of blood flowing through the wrist and thus calculate the frequency of heart beats from the data gathered.
The support page does also state that tattoos can interfere with readings from the heart rate monitor, although other tattoo-related issues are not disclosed.
"Permanent or temporary changes to your skin, such as some tattoos, can also impact heart rate sensor performance. The ink, pattern, and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings," the web site says.
According to Apple-watching web site iMore, only darker tattoos are a real issue. Red and black inks block the Watch sensors completely, although purple, yellow, orange and green are reported to have less impact. Other body abnormalities or skin-related issues, such as heavy scarring, can also derail the heart rate sensors.
Apple has thus far declined to comment on tattoogate.