Should Cameras Cover Entering Or Exiting?

This has always been a question for me. When you are designing a system, do you capture the entry of building occupants or the exit?

I know there are panoramic cameras that can do both but for budgetary, cost and bandwidth conscious customers, what do you recommend and why?

Have there been any studies to suggest one or the other provides more value?


I have always said get them entering and for one reason alone. Usually perps don't run into a building that they are going to commit a crime in, however, they are usually hell on wheels fast getting out the door. My opinion is that you will get more usable frames in the inbound direction.

Now this usually costs more due to the fact that you will likely need a WDR camera, unless there is a vestibule or an additional hallway outside the door that keeps lighting static.

There are a few products with this specific application in mind:

...among others that offer the main advantage of a lower than typical mounting height, and therefore have the potential to collect better quality images.

I am not sure about studies, but I do know that mounting a surveillance camera in a typical spot near a door (on the ceiling) offers poor results. If making people is the goal, the camera must be in a position to do so, and this typically is much lower and more exposed than many think.

I also usually capture them entering, but for a different reason than Jon. My reason is that the door is the choke point and focusing on the door allows for a narrower field of view. That narrower field of view can allow you to get higher PPF and/or use a lower pixel count (i.e. less expensive) camera. (Notice I did not say a "lower resolution camera" - proves I've managed to remember something from my IPVM University class. :-)

If the camera is pointed in, to capture a person exiting, you would normally need a much wider field of view unless there is a long, narrow corridor leading to the door. If there is a long, narrow corridor leading to the door, it's most likely an emergency egress door. In the case of an egress-only door, it would be appropriate to place the camera to capture people exiting.

As Jon noted, if the door the camera is viewing is an exterior door, you will most likely need a WDR camera.

...use a lower pixel count (i.e. less expensive) camera. (Notice I did not say a "lower resolution camera"...

I know there must be a difference because the way you say it, but what is the difference of pixel count and resolution? I've heard that the pixel race has been run out of steam but don't know why.

I flunked IPVM High and so then IPVMU was questionable for me. :o)

Resolution is traditionally a performance metric (i.e., how much can an observer see) while pixel count is a mechanical metric (how many pixels does a sensor have). In IP surveillance, we have unfortunately warped pixel count into resolution. See: Resolution Tutorial and Ban Resolution

Since I not from 'around here', the only place (besides dig cams) that I see the word 'resolution' is about monitors and HDTV's and where they say 640x480 or 1080p, is that still right or wrong way to use it? Different size kind of pixel?

I voted for entrance vs exit for one reason:

Backs of heads don't have faces.

Note: I just added a poll.

As for 'backs of heads don't have faces' that's why they make doorway cameras as mentioned by Brian above. Certainly, they are not widely used but if you want the front of the face going out, a doorway camera is a good idea.

I always like to get them leaving, assuming you can get the camera just above the door. Everyone forgets to cover their faces on the way out. But use a high framerate in case they run.

Ari, how do you deal with the angle issue? Unless the person is walking straight ahead for a while, the angle is likely to be steep, no?

If you've got a "runway", mount the cameras just above the door, in the center, about a foot up. Go to Target; every Target I've ever been to does it perfectly. Otherwise, mount the camera two feet above the door (or 9.5 feet from the ground, whichever is lower), and three feet to the right or left of the door (watch people walking through the exit; most people will angle themselves away from the hinge, so put the camera on the door handle side). A 3.6mm lens with the camera angled down giving you a blind spot of about four feet or so, hanging two feet above and three feet away from a door, gives you a perfect shot of a face, even with baseball hat brims in the way. Try it, you'll see I'm right.

A door camera needs WDR and 30FPS to be useful, although at that range resolution barely matters. I've gotten perps arrested from 420TVL cameras recording at CIF with this technique, although of course lots of resolution is never a bad thing.

We mount 720p covert cameras in the door frame, at average shoulder height. We do either a portrait or landscape aspect ratio -depends on the specific requirements of the site. This has worked extremely well for us.

I always recommend positioning cameras at the door looking inward for several reason. The camera should be as low as possible as the situation allows.

1. We eliminate backlight by having the exterior lights illuminate the face.

2. As the subject approaches the door, their face gets bigger. If the camera is pointed at the door, the subject disappears below the camera as they get closer to the camera.

3. We know what the door is doing. By placing the camera at the door, we see what is going on inside. More useable "background" video.

4. I also recommend placing a camera on the exterior getting a profile of the entrance as well at the exterior area. "Where did they come from? Where did they go?"

They beauty of the surveillance world; We deal with laws of physica that dont' change, the art of the application of the physics,..... and a whole lot of opinions.

This is really an issue of where is the source of perceived threats. For our Law Firm clients the threat of forced entry outweigh worrying what someone is carrying out the door. For our University residence hall clients, there is more day-to day threat from the insiders abusing doors, therefore in that scenario the cameras capture the persons as they approach the door from the inside. Focus on the threat and the question will answer itself. In some cases one may well want both.

I generally recommend both and for differing reasons. One of the most likely "slip and fall" areas in the building is the entry off the street, particularly on the wet day. Many buildings have beautiful polished granite floors which become icerinks when wet. The entry camera will pick up a slip and fall incident and hopefully provide recognition or identification of the person who falls.

The exit camera would also provide footage but would be predominantly used to identify people leaving the building from a security aspect.

In a shopping centre, entrance cameras are preferable to exit cameras (if only one is possible)

Public liablity - there are more trips and falls/slips and falls when customers enter a shopping centre. An entrance camera focussed on the entrance, would capture the incident without obstructions. An exit camera installed externally facing inward, might have the slip/trip incident blocked by doors.

Crime control - criminals enter slowly, but often leave quickly. An entrance camera provides a clearer facial image. Up until 3 years ago, this advantage was offset by backlight issues with internal cameras facing out. The WDR cameras have solved the backlight problem.

Whichever you choose, choose one, not both. When some doors have entrance cameras and other doors have exit cameras, invariably, you will have 2 good shots of the back of the offender's head!

Both if possible. Commercial or shop Entry is best done by covering exterior of entrance in both directions covering street and each other (in armed hold-ups it gets them before they disguise and gets traffic ID or cockatoo's / lookouts for Police) also a head level exit camera with high ppf for facial recognition, with a small monitor facing them as they exit and see own face image. Most crims do some sort of recon, the clearer they see their face on exit the less chance they will come back. Even with a balaclava.

Agree. Both, if funding allows.

Totally agree on the value of the CCTV monitor at the entry for all offenders to check their hair. The monitors nearly eliminated graffiti in toilets, with highly visible monitors placed in the toilet corridor (but high enough to stop monitor vandalism)

And the facial images are the key to crime control - think chokepoints. One at each narrow travelator/escalator landing. Money shots. For evidentiary purposes, also provide police with the seamless video from the low quality offence photo to the high quality chokepoint photo - to counter the defence argument: 'that is my photo on the escalator' but 'that is not me doing the robbery'

Very thoughtful answer across the board!

One thing I don't understand is how people are doing both (e.g., 37% on the poll say both). Are you using multiple dedicated cameras (i.e., one just for entering and another for exiting) or?

What are you trying to capture is the real question! Am I trying to catch faces alone or trying to capture acts of some kind. Most times what a person carries out is not as important as who the person is. In that instance the face is paramount. Where what they are carrying out is more inportant then facial and act are of equal importance. There both entrance and exit count. We have a ball field that we provide security services. In that instance they want to see a person exiting and where they go. We have 2 cameras with immervision lenses, one inside and one outside to capture where they leave from and in what directtion they leave. So one camera inside and choke points and one camera outside at each exit to capture the direction of flight.

Entering if integrated/paired with card access; exiting in theft-prone areas.

The advantage of an entrance camera is that you must approach it through the field of view before you can disable/cover it. A exit camera can be rendered useless with no warning.

We've found that in certain situations, for example shopping malls, perons entering the mall with intent to do wrong, look toward the floor, pull their hat/hood over thier face , or otherwise hide from the cameras they expect to be there. However, on the way out they almost never do and we aree able to obtain an identifying image. We sometimes also identify a few locations that a camera mounted at a lower height will capture facial images of wrong doers as they move from one area of the mall to another without concern for being videoed. The local police have been very happy with both of these approches.

The common wish of retail customers is to view the customer entering the store, but you get a much better picture of the customer if you place the camera to view the customer leaving the store. To do this correctly, you should have two views.

From the point of view of a retailer, both should be covered since the metrics have different uses, specifically calculating the sales conversion. Arrivals are better for reporting. Exiting for scheduling requirements.

If you're interested in understanding the business case, see The Endless Debate on Sales Conversion

For those of you who prefer the camera to capture "entering" (or both for that matter), do you prefer to mount the camera at the door (exterior) facing out and away from the door OR inside the building away from the door and facing the door entrance?

I've always believed an exterior camera mounted at the door facing outward was better. As others have mentioned it gives you a perspective of where the subject came from and might show evidence of vandalism or how the subject tampered with the doorlock. This is the way I've seen it done at many large universities. Of course there is also usually a camera mounted at the door (indoors) facing away from from the door to capture subjects approaching the door from the inside and exiting (similar to the Target example given). Although this requires two cameras I believe it gives better coverage of the whole situation.

Contrary, I see a lot of corporate offices mounting a camera indoors in the drop ceiling or on a wall about 7 to 15 feet away from the entrance facing the doorway. This usually works well for glass doors where you can see the subject through the glass before they enter but also requires a camera with very good WDR.

The door should be covered from the inside, where you can better control the lighting. WDR should be used of course. The camera should be, as you said, roughly 10-15 feet away, looking at/through the door.

If you also want the outside covered, add an exterior camera or two as overview cameras. They don't need to be tight shots, you will have a great identifying shot on the door from the inside.

The reason why you don't cover the door from the outside is you can not be assured that the subject will walk directly through your scene. They could hug the wall, or come from a blind spot. Unless you have a multi-imager, you cannot be assured to get the identifying shot needed. Usually there aren't pinch points outside that are better than the doorway itself. If you have the camera right above the door on the outside, looking straight down, you won't have a decent facial image. If you have it pointed outward at a normal angle, you will likely have a blind spot directly below the camera.

Another reason, the indoor camera is harder to tamper with before being seen by it already. An outdoor camera has a chance of being sprayed, shot, etc from a distance. I know this is an extreme example, but still a consideration to be thought of.

An outdoor camera has a chance of being sprayed, shot, etc from a distance. I know this is an extreme example, but still a consideration to be thought of.

On the other hand, an outdoor camera deters those criminals who are looking for an easier opening;

An indoor one, if not visible, will not. Though it will get a much better shot of the "oh s**t" reaction, and depending on the quality, has a better chance of generating offsetting revenue thru YouTube ads. ;)

I said to still have outdoor cameras. Just the door camera should be inside.

Say you had one camera, which would you do?

I would buy more.

So you typically have 2 or more cameras per door?

I guess this is my exact question. I've always felt you needed two cameras per entrance (to cover exiting/entering or outside/inside views accurately).

That being said, for the folks who voted "entering" as the most important, where would you place the camera if the customer's budget only allowed one camera per door?

I would nearly always go with entrance as with most body language means when they come in the head is up as they are looking around giving you a better ID image. If they have done something usually the head is down making that image harder to get. There will be situations where they have scoped out where the camera is but that would effect an exit camera as well. Try to locate the camera either lower down or further back to make it harder for them to avoid giving an image by lowering thier head

Very interesting opinions and experiences from everyone.

If (a significant if) only one camera, how about (where layout permits shallow viewing angle, tamper avoidance, etc.):

Inside the building.

Viewing sideways for both entrants & egresses (identification by profile).

Shutter speed needs to be short to minimise motion blur.

Of course, every situation is unique, but has anyone got mileage with this idea?