1. Before using this lens cap for the first time, please install the lens cap on the lens and let it stand for 12 hours before using it; 2. Because the front ring of the camera is loose, please directly remove the lens cap and do not remove or install it by rotating it 

Hello,put on the CPL filter or mist filter then screw on the Variable ND on top.Stacking filters in general can create different effects and bring out your creativity. The only caution is that as you put more filters on the lens you can create vignetting or the cutting off of the corners of your picture. This can happen more with wide angle lenses. You’ll also get vignetting by stacking neutral density filters, depending upon which ones you stack and the order you stack them you’ll get varied effects. We don’t recommend stacking a VND filter but if you do, make it the last one because of the threads.  

A professional trail camera is a high-quality camera designed for outdoor use, specifically for capturing images and videos of wildlife in their natural habitat. 

Yes you can. 

If the filter size for your lens any of these adapter ring ( 52mm/ 58mm/ 62mm/67mm/ 72mm/ 77mm/ 82mm) then yes.