このアプリは、ジーメンススターとフォーカスグラフが表示されます。
This app displays two different focus charts with a siemens star. It prevents the phone from going to stand-by while you're adjusting the back focus of your camera or testing your lenses. Swipe left and right two switch between the two charts.
It's a simple but effective tool for cinematographers, photographers and camera assistants.