I've acquired lots of pics of deer checking out my cameras over the years, but I've never seen any evidence that they've ever been spooked by them. I think checking a camera too often does significantly more harm than the camera itself. The camera is simply part of the landscape, like a feeder or stand.
Many of them make a little noise right before the picture is taken, I have seen them react to it. Scent is another thing.
I remember one of the first one's I bought many years ago was the old 35mm with a flash. I was so excited because I was going to get that picture of the elusive bucks that I just knew showed up once I left. Well, I got it all set up and was in the stand. It started to get late and I had 8-10 deer around when a bright white light lit up the world!!! Scared the begeezus out me and the deer (I had forgot it was there). I might as well had shot at them. Ended up getting plenty of pictures on it, but man that first time was a circus
Never did find that elusive night time buck either
Young bucks and does donít seem to mind. I used to use a cuddeback (with a flash). I had lots of pictures good bucks. When Iíd get a picture of a mature buck the next picture was usually of the buck looking at the camera then I never caught them on camera again. I would still see them in the area but not at the feeder. Iím convinced that a flash will scare them. I now use a no glo and they donít seem to mind. All that being said, it will depend on how much pressure is put on the area also.