The single biggest problem is that they generally use fixed-lens wide-angle cameras. We cover these wide-angle cameras in our Optical Range section. Wide-angle cameras don't capture detail regardless of what it says on the box. As a guide, a standard resolution 90-degree angle of view camera can only identify someone up to around 1.5 metres from the camera. Even with HD 1080P this only increases to around 3 metres. The promotional material will often claim these cameras can identify someone 20 - 30 metres away. They can't.
It is unlikely that your installation will use all the same CCTV cameras. We take time to see what you're hoping to achieve then make sure you get the right cameras for each individual location. Sometimes a wide-angle low-detail capture overview camera might be the solution but more often you need to capture higher levels of detail and these cameras can't do that as you move away from the lens regardless of resolution. A camera designed to film people at your door won't be suitable to cover an area 10 or 20 metres away.
Another problem you will often face with these kits is a lack of support both pre-sale, during installation and also ongoing. We are not only there to help you plan an effective system we are also there to help once you've purchased your equipment from us. Feel free to get in touch, we can look at your property online whilst chatting over the phone and put together a package for you.
The claims made by many people selling CCTV are simply laughable. We made a video to highlight the discrepancy between what the advertising blurb says and what you actually get using a Swann camera typical of the type sold in a kit by Maplins, Costco, Screwfix, electrical wholesalers and any number of online retailers. It claimed an effective range of 25 metres and our MD often said he would happily stand stark naked 25 metres away from one. We took him at his word. The result is at the bottom of the page but we warn you now it's not pretty!