Nikon D3400 lent to girlfriend for Halloween. Now half of the live view image is totally black; same on photos but not on menu displays.
She "cleaned" it before returning, so is my sensor toast?
Looks like the shutter's getting stuck to me. I say that because the amount of visible photo changes between shots. It's simple enough to confirm too.
Look inside your camera. You should be able to see the whole sensor.
I suspect you'll only be looking at a portion of yours.
Fixing that probably means a trip to a Nikon Service Centre but —assuming it is a mechanical problem— other camera repair shops may be able to see what's wrong and fix it without spare parts.
It may be (he said shuddering) a bit of cotton wool jammed in there. You may even be able to carefully remove the blockage yourself.