Phone going blank while digiscoping

[bbags8]

Sorry for the newbie question but…

While digiscoping with my phone cam adapter and either and iPhone 10 and iPhone 15, as I zoom in with the phone beyond 3x, the phone image goes blank. Intermittently it will let me briefly zoom to 10x and then go blank.

What am I missing?…Thanks!

 

[BBob]

Camera lens is switching when you zoom. Use an app that locks the camera lens.

 

[bbags8]

Camera lens is switching when you zoom. Use an app that locks the camera lens.

Thanks!…

. Is there a recommended App for digiscoping?