The smaller the lens, the wider the angle and the more backed out the image will be. Larger is the opposite. Clarity is more about the image sensor itself, while the distal and lateral coverage is more about the lens. Personally I stick with 4s unless a specific scenario calls for otherwise. 2.8mm is a near perfect 90 so is great for corners, I however have been comfortable with 4s in corners just because in most cases I don't need a perfect 90. 75 or so degrees for a 4mm is fine by me. I agree with
@pghcamman on this for about the same reason. I'd rather shave off some viewing angle to trade for some closer detail. It's an inverse relationship between the two.
4MPs work perfectly fine with 7600 series NVRs. I have a few systems set up in this manner and they work pretty well.
Never purchased from there. As long as they are western-regioned cameras, you have nothing to worry about. Even if you decide to play Russian roulette and purchase Chinese regioned cameras (NEVER purchase a Chinese regioned NVR) as long as they say multilanguage that means the region is patched to western region and they will work with western region NVRs without any fear of the infamous language mismatch error. I mix pre-patched Chinese cams with US NVRs all the time, for me it's a sensible combination, but I know what my risks are and am willing to take them. There is an infinite amount of documentation on here about regional restrictions. No need to take my word for it.
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