I'm not sure how large mature whitetails would react but I have a stand over a bait pile. The trail to my stand I use goes about 15 yard from my bait pile and makes a half circle to it then goes right past it. I used just a regular flashling, no red lense, walked within 15 feet of three deer standing at the pile. They didn't know I was there until I looked up, saw three figures, then shinned the light on them wondering what they were. They were not old mature deer, I believe they were a doe and two fawns, but they didn't seem to mind the light at all. I think a red lense would help even more, but my opinion is deer will spook less to a light if you shine it at your feet and not far up ahead of you than to someone crunching through the brush. Yet, my experience wasn't with an old mature buck