Over the years I had one flash and two IR cameras. All have spooked deer in my opinion as the first pic would be them looking towards the cam, second pic alert and by the third pic them fleeing. I think a lot of it is like what Greybeard11 said, a matter of how I had them set up. Take time to put the camera to the sides of trails so their attention is not focused on the camera as it approaches. For feeding sites many recommend putting the cams up higher and pointing down. That way flash cameras may appear to be lightning and the IR cams will likely go unnoticed. Can't beat flash/color night time pictures. Over the years of looking at my IR pics I am just tired of the blurry pics if the deer is moving.