Camera lens options and views
Camera lens sizes matter
Picking the right lens for your cameras is very important. Going with a verifocal lens will allow you to adjust the view in order to see exactly what you need to see. Many big box stores will only give you a wide angle lens and you may not get the view you want. As you can see from the pictures of the overhead door, if you get a camera that looks at just one door the people will appear larger but if you are looking at 3 doors at once they will be much smaller.
Now with mega pixel cameras you can zoom in after the fact and since the resolution is 3-5 times better with the high definition cameras you can get much more detail in a wider angle view hence you could zoom in to what normally would be a 12mm view after the fact but you would still record the entire room.
If your person or object is 60 feet away and you are using a 2.7mm lens then the horizontal view will see about 90 feet across and about 68 feet high making the 6 foot man in the picture only take up less than 1/10th of the picture. When you use mega pixel cameras you can zoom in after the fact but you should still pick the best lens for the application.
A 8mm lens at 40 feet away would see 22 feet across and 16 feet high so if you needed to see the man door and the overhead and the windows above then an 8mm might be your best choice.
Many times we recommend verifocal lenses so they can be adjusted to get the best view for your application. (These can be changed later on.)
If you need recognition the 4mm lens above will almost see the entire room although when you need identification the 12mm lens will give you a much better face shot as long as the camera is angled properly. Many times we will install more than one camera in order to get the very best pictures for looking at areas like parking lots.. The chart above will give you a good idea that if you use a wide angle lens you will get more in the picture but people will appear much smaller.
When you look at a 12 foot overhead door from 40 feet away in a warehouse using a 2.7mm lens your view will see 63 feet across and 49 feet high. Now since the warehouse is only 23 feet high you will see ceiling and floor and whatever is on both sides of the overhead door.
The exact lens for this application to see the overhead would be a 12mm and it would just see the overhead door with a foot extra view on each side and only 11 feet high so anyone coming in would be viewed in much higher detail and a man would take up ½ the height of the screen.