I don't think it was the red light that he was looking at but your sent on the camera or tree is what he was smelling ! It is amazing to me that those big bucks can smell just about everything even when you spray the camera down or use latex gloves to change cards ! I have had smaller bucks and does walk right by my cams without even showing any signs of smelling it or me and then had a big buck come down the same trail and smell the camera or my scent from about 20' away and stood there for about 5 minutes smelling and licking his nose and then cautiously continued on his way ! Plus I always try to change my cards right before we get rain hoping the rain will wash the scent I do leave off the camera !
I set mine out directly on a trail and the first couple deer stopped and looked at it for a few seconds then continued on. In the past I have had some deer see the camera and bolt while others never notice it so its a toss up as to what messes with them.
I do know that a coyote found my one camera and has enjoyed attempting to snack on it.
Yes they do... They hear the click as well as the flash. All I can say is get the better cameras, hide them well or lock them up. You will not be disappointed. The amount of camera's I run all year is really excessive but once I changed to the black out type and the silent cameras, my numbers increased as well as quality of mature bucks that they will capture. I know it is a small click, and the infrared is just a small flash, but educating them to anything out of the ordinary will diminish your chances of getting those cagy old bucks and seasoned does on camera... I have seen it from the stand, the sound just trips them out! I have been having really great luck with the WG Vision extremes and the new Mirages. No flash, no clicks, no problems. Good luck!