Using a third party app is BS. Only the camera app that Apple provide allow me to use it directly without log in.
Why BS? Apple provides the second lens for your use. Its own camera app is the equivalent to an auto mode on any camera -- it makes the best decision it can under the circumstances. That includes the use of the second lens in at least two situations: where light and other conditions permit or where the second lens can assist with depth perception (i.e., better portrait mode shots). For those users who want more control (i.e., defeating Apple's defaults), Apple has made the camera API available to developers. What more would you want?