How Far Can I See With My Cameras?
"I have seen some cameras on line and want to get some, but I want to get good pictures. How can I know what I will actually see?"
A great question, which depends on what you expect to see on your monitor or phone. It's not so simple an answer, so read on.
Essentially, a security camera set up in an open space can virtually see forever. However, how far your target, criminal, or whatever you want to see, is distanced from a camera, is another matter if you want usable video. Distance vs camera lens vs camera type determines whether or not target / person is readily identifiable or just a few coloured pixels on your video monitor. The size of the subject on the recorded image is determined by the number of pixels assigned to the “target”. The less pixels, the smaller the image, so if you try to zoom in or increase the size, the image can be pixelated and useless. Regardless of what you see on Hollywood TV cop shows, there is no such thing as video enhancement software to make a blurry or pixelated image sharp and clear. It doesn’t happen... if the image is pixelated, then that’s what you get. To start with, you need the correct lens for the job application.
Back to the not so simple answer – a term used in the security industry to measure the size of an object on recorded video, is known as Pixels per Foot (PPF). PPF is a measurement of quality of the final video produced related to the size the area that is recorded.
An simple example: how many pixels would a vehicle rego number plate take up at a certain distance?. Assuming a number plate was about ONE FOOT or 30cm wide. If the number plate is 100 pixels wide in a recorded image, then the scene at that distance is 100 Pixels Per Foot.
So… essentially to get a good usable recorder image you need to assign a good amount of pixels to the areas that you want to view, and this initially relates to the camera lens that you choose. The other thing is number of pixels in the camera itself, more on that in another post.
The easiest way to explain it is with the following images.
Here we have 4 different focal length cameras all looking at the same targets- vehicles and the front entry of the house.
The lower the focal length lens number, 2.8mm, gives the widest angle of view, but the part of each image is smaller, or less PPF. Images at further distance don’t contain enough pixels, and the recorded images will be seriously pixelated when attempted to enlarge, hence no use to police.
The higher the focal length number, 12 mm, has a narrow angle of view, but the target is bigger. More PPF, easier to enlarge the image and more usable to police in the case of evidence.
How many Pixels Per Foot do I need?
Eversafe Security can help you with determining that. Which is why we prefer to inspect your home or office and discuss with you, what you are wanting to achieve and design the system on a case by case basis to get it right.
There are many, many choices and outcomes that an on-line kit won’t provide you.