People are afraid that if they turn iron mask off they won't find anything but shallow targets and if iron is even close it won't see even those targets. Since the beginning Minelab has said that if your hunting in bad ground or in thick trash and iron turning iron mask off would give better performance. As far as the benefit of using iron mask on, Minelab clearly states that "circumstances may arise" that a target "could" be lost with iron mask off and then adds "depending on settings and conditions". The benefits of turning it off far outweigh the the limited benefit of having it on in the conditions above. Good ground, low EMI with moderate iron > use iron mask on. Bad ground, high EMI with high concentration of iron and trash > use iron mask off. It's as simple as that.