For smartphones equipped with multiple camera lenses, Frontier Pulse provides a helpful guide to determine the correct lens for heart rhythm measurements: 1. Start the measurement process in the app. If you encounter a 'Prepare' screen, follow the prompts until you reach the 'Find your camera' instruction. 2. On the 'Find your camera' screen, you will see a visual guide indicating which camera lens to cover with your finger. The correct lens will cause the on-screen circle to darken or turn red, indicating that your finger is properly placed. If you cover a different lens and the circle displays your surroundings, switch to another lens and try again. 3. Once you've identified the correct lens, proceed with your heart rhythm measurement as directed by the app, ensuring not to cover the flashlight with your finger to prevent overheating. Following these steps will help you utilize the appropriate camera lens for accurate heart rhythm monitoring with Frontier Pulse.