Yes! It is very possible to take photos with your Nokia Lumia without unlocking it. This is an ideal feature especially for those who want to take emergency photographs yet with very complicated passwords to their phones.
It is very simple to take a photo in such situations. All you need is to press on the Camera Key by the side of the phone. This should prompt the camera to open even if the screen is locked. However, in order to view the photos taken, you will have to unlock your phone and go to the gallery.