^+1 This!!!!!!
We often tell the NOOB when they come here and post that they have experience with DSLR cameras that they might have to forget what they know about DSLR and high end photography cameras LOL as they play with these. Almost everyone that has come here with experience in DSLR cameras struggle with these cameras, and many fall for the more MP is better!
It is just a matter of managing the expectations of a cellphone camera or DSLR camera versus a surveillance camera.
Every one of these surveillance cameras have more processing of the images than a DSLR camera or cellphone camera. Some are worse than others. Then there is the compression of the video, etc. Turn off NR on one of these cameras and you will see how much processing is used.
You will find a BIG difference between photography equipment and these cameras. Digital zoom works better on regular cameras than these. The sensors and optics just are not at the same level.
These cameras are designed for 24/7 use with abuse from the elements.
DSLR cameras or a cellphone are designed for a different working environment and purpose. Hang a DSLR camera outside and see how long it lasts LOL! But the quality would be better for the time it was working (but also a lot more storage needed too).
Another example, you can see individual hairs and skin pores with DSLR photography equipment or even an iphone camera and you won't with these kinds of cameras. These are for a different use and different expectations.
- Sensor Size - a full frame DSLR sensor size is 864mm^2; whereas a 1/2.8" sensor popular on many cameras would be 20mm^2, so the "real" camera can collect over 40 times more light than a surveillance camera. And this doesn't even account for less light available for an 8MP versus 2MP for the same size sensor.
- Shutter Speed (Exposure) - Taking a picture with a "real" camera, you can slow the shutter down to 1/2s or longer for a nice clean picture of a person not moving. Perps rarely stand still and we need a shutter of at least 1/60s to minimize the blur.
- Aperture - With a "real" camera you focus on a specific part of the field of view, while a surveillance needs to focus on things in the foreground and background, which means the aperture is smaller, further compounding the light issue.
- Compression - A single 8MP image from a "real" camera could be upwards of 5MB of storage. In surveillance cameras, if you record at 15FPS, every second of video could be 75MB or more, which could equate to 6.5TB per day per camera. Obviously most are not going to have that kind of storage, so lossy compression algorithms are used to reduce storage and network bandwidth requirement, and that can add noise.
- Environment - a "real" camera is used mainly under ideal conditions, whereas a surveillance camera is going 24/7 in every type of element, so the design and size impacts its capabilities.
The goal of surveillance cameras is to capture clean images with enough detail for the police to go with. That is why it is important with these cameras to purchase ones on the ideal MP/sensor ratio and with the ability to actually set parameters and the camera adhere to them.