If your looking at buying a Trail/Farm Cam, the most important thing to look at is the initial start up time that it takes from the Camera sitting in an idle mode to the time of taking a image. It works the same way a PC computer does in the sense of start up from idle to being able to use it. (Without the sounds of high revving fans etc) There's no use having a camera that will take images after an object has move past the sensors.
The other important item is the SD memory card. A SD card of 8gb is about average of what the cameras would need. Anything smaller and it may not hold all the images and will work slower. (Remember cameras take images of anything that moves including tree branches, leaves, fox, goat, pigs etc).
I have used the Reconyx, Simmons and Scout Guard brands. They are around the $700 mark with the Simmons about $300. It all depend's what you are using the camera for. If its personal security on remote properties then these cameras are the go. Have a look in their website. The cheaper eBay ones will take good images and work ok, however I recommend that the start up time is looked at before purchasing.
My two bob's worth.
