Put one phone where the photo is. Frame and shoot from the other.
Scan with the other phone’s camera. Not needed if this phone is the camera.
Put both phones on the same Wi-Fi, or one on the other's hotspot. Then:
Video and photos go straight between your phones. Nothing is uploaded.
Starting the camera…
Point this phone at the code on the other phone.
Prop this phone up and use the viewer to take photos.
Your browser will ask to use the camera. Allow it so the phones can find each other on this Wi-Fi. This phone's camera stays off.
Point this phone at the code on the camera phone.
Making a reply code…
Some Wi-Fi networks block devices from talking to each other. Try turning on a phone hotspot and connecting the other phone to it.