I develop Stillspin, an iPhone app for checking rotation speed. It's on the App Store now. One odd thing about a strobe: an object can look stopped at more than one speed. After you lock a setting, Stillspin shows the other possibilities instead of just leaving you with one number. For record players there are 33⅓, 45 and 78 RPM settings. There's also a camera mode that watches a paper marker on the platter, with the phone sitting beside it. The strobe is free. Camera and sound RPM, cross-checking and the camera turntable screen are a US$3.99 one-time unlock; regional prices vary. No account or subscription. iPhone, iOS 17+. It's a hobbyist tool, not a calibrated instrument or a wow-and-flutter meter. Flashing-light warning applies. https://apps.apple.com/app/id6810664581 I'd like feedback on that first part: does seeing several possible speeds make the result clearer, or does it need more explanation?   submitted by   /u/Life_Yogurtcloset_52 [link]   [comments]