What is an IP camera?

In an analog camera, a video cable runs to a recorder that converts the signal into a picture. An IP camera does that work itself. Inside the camera is a small computer that captures the image, compresses it, and sends it as data over the network. That's the whole difference in a nutshell: the image has become data, and data can go anywhere your network reaches. That has practical consequences. The camera gets its own IP address, just like your laptop or printer. It can receive power and data over the same cable (PoE, more about that later). And it can simultaneously send to multiple locations: to a recorder in the utility box and to the app on your phone. Most IP cameras send two streams at once. A high-quality recording, and a lighter version that you can see in the app when you watch live. That's why live footage on your phone sometimes looks a bit less sharp than the recording you watch later. That's not a malfunction, that's the camera that is missing your mobile connection. Wireless IP cameras also exist. They send the same data stream, only via wifi instead of a cable. Useful where a cable cannot be placed, but you are still dependent on your wifi range and you still need power in that place.

An NVR is a Network Video Recorder: a box with hard drives that captures and records the streams from your cameras. It is the place where your recordings are stored. The name says exactly what it is, a recorder that receives its video through the network instead of through separate video cables. How long you can watch back depends on three things: the size of the disk, the number of cameras, and the bitrate. Bitrate is the amount of data a camera produces per second. Higher means sharper images and more detail in motion, but also a disk that fills up faster. If the disk is full, the recorder starts recording over the oldest images. That is normal behavior and you set yourself how many days you want to store them. A second way is cloud storage, where the images are stored outside the door. Advantage: if someone brings the recorder with them, your footage will still be there. Disadvantage: you need a stable internet connection with enough upload speed, and it is a continuous service rather than a one-time purchase. Some cameras also have an SD card slot for recording inside the camera itself. That works for a single camera, but is vulnerable for the same reason: the recording is stored in the device that can be removed.

PoE stands for Power over Ethernet. The network cable then provides both the data and the power, so you don't need a power outlet near the camera. This saves work when mounting under a roof edge or on a wall. The power comes from the NVR or from a PoE switch. When choosing, pay attention to the cable quality and the distance, because a PoE connection has a practical limit of about one hundred meters per run. ONVIF is an agreement between manufacturers about how cameras and recorders communicate with each other. If both sides support ONVIF, you can in principle connect a camera from one brand to a recorder from another brand. In principle, because ONVIF covers the basic functions: image, recording, some settings. Brand-specific smarts such as certain detection features often work only within the same brand. If you stay within a brand, those brand-specific features usually work. Night vision works with most cameras with infrared LEDs. The camera switches to black and white in the dark and illuminates the image with light that you cannot see yourself. There are also cameras that continue to shoot in color by using an extra sensitive sensor or a white spotlight. Color in the dark helps in recognizing clothing or a car, but white light stands out and that is not desired everywhere. Finally, resolution. More megapixels is not automatically better. What you want is enough pixels on the area of the image that matters. A camera that covers a wide area provides little detail per face, no matter how high the resolution is. Focusing better on a door or driveway provides more usable image than having more megapixels over a too wide angle.