Use a solar battery charging system to power day/night security camera?
I very much doubt the adapter says "12 v @ 700 mAh". AC-DC converters are rated in mA, not mAh (mA is current, mAh is electric charge).

If the adapter for your camera says "12V @ 700mA" and your batteries are 12V, 800mAh, then it won't work very well. 800mAh means the batteries can supply 12V, 800mA for one hour. Or 400mA for two hours. In the ideal case.

Realistically, you won't get full capacity (maybe 600mAh if you're being optimistic), but the camera probably doesn't draw a full 700mA. Let's say it draws an average of 400mA (I have no idea what it draws, you'd have to measure it to figure it out). Then the batteries will run your camera for an hour and a half. Not so great. You either need more batteries or a camera that draws less current.

Also, to properly charge the batteries, you can't just connect the 12V solar panel to the 8x 1.5V batteries in series. You need a DC/DC converter/charging circuit to manage the batteries and, ideally, to run MPPT to improve the solar panel efficiency.