What a great debate-flash vs IR... I talk with friends about this all the time. I have used both and both have proven to be effective and both have proven IMO to scare and educate deer. I started with the 35mm+flash cams and again IMO I think I educated deer more with the sound of the camera moving the film and by adding the flash that gave them more reason to not stick around. Unless I was using bait, I never had a buck more than 3.5 years of age visit a camera site more than once with the 35mm+flash cam (unless it was over bait or some other man placed object).
My hunting partner and I switched to only using digital flash and IR cams after a couple seasons of poor results with 35mm cams. We used Leafyriver digital flash and M.A.D. Wildlife Eyes which are IR video cam units. IMO deer didnt spook as much and came back more often with the leafy river verses 35mm flash. The M.A.D. Eye is a "huge unit" compared to most cams of then and now but that seemed to scare or educate deer even less than the digital flash cam. However, I have video on more than a handful of occasions that the mature bucks (3.5 yrs old IMO) pinpointed the M.A.D. IR video cam with its 10+seconds of IR "red glow" and they head bobbed back and forth and at times spooked. Now when we had bait over the cams deer would frequent the cameras without much regard to the cameras flash or IR glow.
I currently use 2 IR cams now in a county where baiting is prohibited completely. I have a number of pics this year from mature bucks that walked by the cameras during the day and nite. Most of my IR pics of mature bucks are looking right at the camera which leads me to believe they are noticing it and are not coming back to that specfic spot, especially the pics taken at night.
Now I totally believe that the camera is not the entire problem by itself. By walking anywhere in the deer woods I am leaving scent of all kinds, making noise, leaving a camera that is not 100% scent free. And then I do this whole process on a weekly/bi-weekly basis to check the cams themselves and not to mention the hunting I am doing as well is leaving a trail behind that might be educating the deer too.
I am not ashamed of the gospel, because it is the power of God for the salvation of everyone who believes: first for the Jew, then for the Gentile. Romans 1:16