The latest craze in the hunting industry is obviously cellular trail cameras or game cameras as some call them. This is especially true this year with the release of the Reveal Cellcam by Tactacam. This camera is in a price point that is more than affordable while reliable for a larger group of hunters than ever before. Because of this so many people now have instant 24hr access to photos being taken by their trail cameras while they are miles or even thousands of miles away.
One common complaint I'm getting calls about and seeing on social media groups are foggy pictures especially this during the early morning hours. I have even had customers wanting to return their cameras because of it. They were convinced it was the camera simply because all their camera's were not having the issue until I had them swap camera's between locations and the problem didn't follow the camera.
I can't say that cellular game cameras fog up more than non cellular, cellcams just tell on themselves instantly. I can say that both experience the same thing and have for as long as I can remember. Especially certain times of the year and some set ups seem to be more prone to fogging than others. Recently I had a Tactacam Reveal that was on the edge of a food plot about 3' off the ground getting foggy pictures about the same time most mornings. So I removed that camera and replaced it with another camera that was not getting foggy pictures in its previous location. This camera is higher end RidgeTec Lookout 4glte Cellular Camera. The following morning the same thing happened with the Ridgetec. The pictures were fogged up just like with the Reveal and lasted for several hours. Now previously this camera was not having this problem where I had it mounted down in the bottom under bunch of trees but on the edge of this food plot it is now experiencing the exact same foggy pictures that the Reveal Camera had. I haven't been to the cameras when they were experiencing this but I can say I have never found moisture inside them so I'm pretty sure it's forming on the outside.
So why is this? What is causing the camera lens cover to fog up. Moisture is forming on the lens cover much like your bathroom mirror when you take a shower. I'm not a meteorologist so I'm no expert on temps, humidity or dewpoints so I had to do some research on those three topics but basically it comes down to the temperature of the lens cover and the dew point. Dew point temperature is the that the cooling air must reach to get to 100% humidity. Once it cools below this point the air can't hold any more moisture and water droplets form as condensation. As the lens cover temperature cools it can drop below the dew point, water droplets will form on it especially when there is no breeze to keep them from forming. On days when dewpoints are lower the likelihood of moisture on the lens developing is lessened.
What can we do about it? Unfortunately I have never found a 100% solution. I've tried many antifog products and none have eliminated it. While it didn't eliminate it all together it did reduce it and it seems to disappear faster. Below are 4 images from two cameras on two consecutive mornings mounted beside each other. Both are treated with anti-fog. The cameras are Stealthcam Revolver 360 Pro and a Reveal X 3.0. 
If you find moisture inside the camera then that is another issue and you should contact the camera brand support department.