I'm new to the trail camera thing but have had a few pictures where it is hard to see what triggered the camera. I have my Bushnell camera set to take 3 pictures each time it is triggered and it does so in fairly short order, I'd guess it usually gets the 3 pictures within 2 seconds.
Today a friend showed me a really easy way to spot differences, and therefore stuff that moves, between the frames. Thanks Gerry, I hadn't thought of this...
Simply select the image files on your hard disk or desktop, in my case it is 3, either in windows explorer or on your desktop if that is where you saved them (if you click on the first image and then hold down the Ctrl key this will allow you to select other, additional images) and then right click on the highlight images and select "Preview"
This will then open the first image in a viewer window and if you hit the right arrow on your keyboard the second image will open replacing the first, right arrow again and the third will open replacing the second. The first time you do this it may take a little while to switch between images as it has to load them but once you've done it a few times the pictures should be in memory and so the transition should be seamless.
As a result you can view the images one after the other very quickly and if anything has moved between the frames it immediately jumps out at you. The effect is really quite remarkable and it is one of the methods used to detect new objects in the night sky - astronomers switch rapidly between images and any new object is easily seen.
I will attach 3 images that you can try this with, if you right click on them you should be able to save the images, one after the other, to your own desktop or computer hard disk and then you can select them, right click, select "Preview" and use the right arrow to page through them. You will be amazed at how easily the deer jump out at you. In this case until I did this I hadn't seen the 2nd deer in these 3 images.