Buying the 4MP version and not the 8MP will work.
Dropping the resolution/Downrezing a camera does not work - It is still using the 8 million pixels - the camera doesn't change the "pixel resolution screen" on the camera when you go from 8MP to 4MP. The sensor still needs 2 times the light going from 8MP to 4MP, so the native 4MP camera will result in a better image at night. The firmware will make some algorithm attempt at downrezing it, but it could be a complete crap image or a somewhat usable image, but if there is a concern that the 8MP isn't performing or wouldn't perform well at night, then it is better to go with the 4MP.
I have a 4MP and 2MP on the same 1/2.8" sensor and the picture quality is quite different between the two and the 2MP kicks it's butt at night.
In most instances, you want to get a camera that will perform at your location for the worse situation, which for most of us is at night when it is dark and there is little to no light. If a camera performs at night, it is easier to tweak settings to make it work during the day than it is the other way around.
My 2MP cameras outperform my neighbors 4K (8MP) cameras....why....because they are both on the same size sensor.
When we had a thief come thru here and get into a lot of cars, the police couldn't use one video or photo from anyone's system but mine. Not even my other neighbors $1,300 8MP system provided useful info - the cams just didn't cut it at night.
My neighbor tried the "I will just downrez the 8MP to 2MP" and the image was a soft dark mess.
His system wasn't even a year old and after that event has started replacing with cameras on the ideal MP/sensor ration based on my recommendation and seeing my results. He is still shocked a 2MP camera performs better than his 4k cameras and he cannot figure out why downrezing from 8MP to 2MP doesn't work properly... It is all about the amount of light needed and getting the right camera for the right location and downrezing doesn't change the physics of the camera.
