You cannot run on auto/default settings - this results in motion blur ghost instead of a human. Your camera is a little high, but it should work.
Once you dial it in to your field of view, and do the global config to calibrate the camera, then you will start to see results.
I have got IVS to work in a blizzard:
and this crazy shot where I will preface this with this camera is dialed in to this location for when the flood lights come on, so that is why the picture is so dark. One of the big issues people do not account for is what happens when a floodlight comes in - if the camera is on auto/default settings, the image will look ok when the floodlights are off, but then the camera gets temporarily blinded when the floodlights turn on or the image is too bright and it misses IVS motion. So the best option is to dial it in for when the floodlight is on knowing that they will kick on and you will get a great capture once they do.
It comes down to configuring your camera and dialing it in to your field of view and using a test subject to walk around while you are adjusting with the IVS rules on during live view to see when and why it is triggering.
Auto/default settings are usually going to be problematic. Auto shutter at night was probably a motion blur ghost and didn't look like a human.
And some field of views will be problematic as well. YMMV.
In my opinion, shutter and gain are the two most important and then base the others off of it. Shutter is more important than FPS. It is the shutter speed that prevents motion blur, not FPS. 15 FPS is more than enough for surveillance cameras as we are not producing Hollywood movies.
Many people do not realize there is
manual shutter that lets you adjust shutter and gain and a
shutter priority that only lets you adjust shutter speed but not gain. The higher the gain, the bigger the noise and see-through ghosting start to appear because the noise is amplified. Most people select shutter priority and run a faster shutter than they should because it is likely being done at 100 gain, so it is actually defeating their purpose of a faster shutter.
Go into shutter settings and change to
manual shutter and start with custom shutter as ms and change to 0-8.3ms and gain 0-50 (night) and 0-30 (day)for starters. Auto could have a shutter speed of 100ms or more with a gain at 100 and
shutter priority could result in gain up at 100 which will contribute to significant ghosting and that blinding white you will get from the infrared.
Now what you will notice immediately at night is that your image gets A LOT darker. That faster the shutter, the more light that is needed. But it is a balance. The nice bright night image results in Casper during motion LOL. What do we want, a nice static image or a clean image when there is motion introduced to the scene?
So if it is too dark, then start adding ms to the time. Go to 10ms, 12ms, etc. until you find what you feel is acceptable as an image. Then have someone walk around and see if you can get a clean shot. Try not to go above 16.67ms (but certainly not above 30ms) as that tends to be the point where blur starts to occur. Conversely, if it is still bright, then drop down in time to get a faster shutter.
You can also adjust brightness and contrast to improve the image.
You can also add some gain to brighten the image - but the higher the gain, the more ghosting you get. Some cameras can go to 70 or so before it is an issue and some can't go over 50.
But adjusting those two settings will have the biggest impact. The next one is noise reduction. Want to keep that as low as possible. Depending on the amount of light you have, you might be able to get down to 40 or so at night (again camera dependent) and 20-30 during the day, but take it as low as you can before it gets too noisy. Again this one is a balance as well. Too smooth and no noise can result in soft images and contribute to blur.
Do not use backlight features until you have exhausted every other parameter setting. And if you do have to use backlight, take it down as low as possible.
