This app offers a slider to control a simulation of shutter speed which is about as good as you might expect from a digital camera, however the max shutter speed you can set is about 1 second, when actually users might want a a much longer time like 10 or 20 seconds to get nice smooth effects. So it’s not powerful enough to achieve smoothing effects that most users would want. The app is ad supported which is fine, ads are prompted when you change aspect ratio. This is fine but there are some ads that are in Chinese and so it’s impossible to know which button to press to decline the offer and continue. Overall, I would say keep looking unless you are only needing a very small smear effect from shutter speed.