Differences between Megapixels and Lens Sizes
2 Megapixel 4mm Fixed Lens
4 Megapixel 4mm Fixed Lens
4 Megapixel Adjustable Vari-focal Lens 2.8-12mm
Selecting the proper resolution and lens size is key to getting the image clarity you desire. The wider your shot is left to right, the less detail you are going to see. The tighter your shot, the move detail you will be able to see.
Picking the proper lens size...
Indoor cameras -
Cameras mounted on ceilings or walls between 8-15ft would want a 2.8mm fixed lens.
Cameras being mounted indoors in warehouses or locations above 15ft would want a fixed 4mm lens.
Outdoor cameras -
For cameras being mounted outdoors picking a proper lens is all about what you are trying to accomplish versus cost.
You options vary from a Pan Tilt Zoom camera, vari-focal or fixed lens.
Pan Tilt Zoom cameras allow you to move the camera left, right and zoom from the recorder, smart phone or computer.
The most common outdoor camera is a vari-focal lens. This allows you to adjust the field of view to exactly the right amount of width and detail (like picture three from above).
As always, cost matters when buying something new. A fixed lens 4mm camera would be the next best option to go with for an outdoor camera. You will not see as much detail or see as far as you would with a vari-focal lens but you save yourself some money.
The last option would be a 2.8mm fixed lens. It will make it so you can use less cameras to cover more area but you will not have as much detail or be able to see as far.
Picking the proper megapixel camera...
As you can see by looking at the images above the higher the megapixel camera the more detail you will see up close and afar. Using the images above as a guide, talk with your installer about how far away from your camera you want to see and clarity you want to see.