Part one below is about properties. There's more to it than that, but unfortunately it gets harder to deal with, simply because there's a lot less research to guide you. If you know the physical properties of a camera, you can do a pretty good job of specifying its capabilities. However, knowing that stuff does not predict what kinds of pictures you are going to take. Same way, you need to know a lot more than just the capabilities of eyes to make an educated guess as to what an animal actually sees.
Think about a digital camera for a sec, one with a super-wide-angle lens and great focal depth, that is on and recording all the time. Next, take two of those and set them so that their fields of view overlap some, but are mostly separate. Make the recording field for each one something reasonable, maybe 40-50 megapixels (roughly the number of photoreceptors in each retina of a large monitor). Now, think about how you are going to process that live video feed in a brain the size of a pencil eraser....
Right. Something has to give. How that works in a reptile is something that we don't understand very well by being mammals. In vertebrates other than mammals there are several layers of neurons in the retina itself that appear to 'edit out' much of the original data, so that the animal's brain does not actually receive most of what the eye records. We mammals lack those retinal editing circuits, and thus our brains get the straight video feed. There is some evidence that nonmammals may only "see" those things that are moving. This might actually capture most of the information you need – if you are stationary, only those objects that are moving are "seen", whereas as soon as you move, the whole world "moves" and you can see where you are going.
I am not sure that I buy this concept for monitors, but there isn't any experimental work on them that I know of. For one thing, it would predict that an animal resting in a cage in a quiet room would "see" nothing, and probably wouldn't be doing anything about it. While this may be a fair description of life in captivity for some herps, monitors I've had will lie still and keep looking around, using only eye movements. They might well have more "live feed" than has been shown for other reptiles, but their eye and brain circuitry is so different from that of mammals (the two having last had a common ancestor around 300 million years ago) that you're not likely to figure it out by assuming that they see things just as we do. Almost certainly they don't.
Bottom line, we know from physical structures that monitors can see very well indeed in the daytime, and physically cannot see beans at night, but we do not have the go-ahead from that information alone to say very much about what they actually perceive.
