Camera Field of View (FoV) Guide

By IPVM Team, Published Nov 13, 2019, 10:00am EST (Info+)

Field of View (FoV) and Angle of View (AoV), are deceptively complex. At their most basic, they simply describe what the camera can "see" and seem self-explanatory. However, when analyzing images, comparing cameras or projecting quality, subtleties in these calculations can have a big impact.

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In this tutorial, we examine:

  • Specifying Field of View And Angle Of View
  • Other Field of View Terms
  • Calculating Field of View
  • FoV Width vs. Coverage Area
  • Measuring / Comparing FoV
  • Field of View vs. Target Distance
  • Field of View Requires Distance Notation
  • Field of View vs. Lens Length
  • Field of View vs. Imager Size

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Comments (17)

Great report IPVM team. The VFoV is often overlooked. You scope out the site, recommend the best camera for the situation and then, wham, you don't see all that you want because the VFoV wasn't enough and you didn't check that spec of the camera first. Not an issue most of the time but sometimes it is, especially if the camera is looking at a scene that is really close. Some camera manufacturers list this on their data sheets but many don't.

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A lot of people don't consider it when planning the camera's installation height compared to the scene either.

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Great article and I always learn from these, but I disagree a bit with your last paragraph that imager size is not a major factor in determining FoV "as variances among imager sizes tend to be modest". While it is true that the variances are modest and may seem inconsequential, it cannot be ignored that there is an impact.

Take for example two common imager sizes nowadays in cameras; the 1/2.8" imager often found in 1080p cameras and the 1/2.5" imager often found in 4K cameras. Of course, this doesn't catch all models with all manufacturers, but these are indeed common. The above imagers when converted to mm to measure size again seem inconsequential in their difference as one is 9.07mm and the other is 10.16mm, respectively, but again has a real impact.

I always learned my FoV calculations in metric and while it takes a moment to learn it, it's fairly straighforward. FoV = imager size divided by desired vertical height multipled by distance.

So, if you are attempting to capture a person walking into an entry way and need an 8 foot vertical height and the distance is 20 feet away, the calculation looks like this...

1/2.8" imager

9.07mm divided by 2434mm (8 feet) multipled by 6096mm (20 feet) = 22.71mm lens

1/2.5" imager

10.16mm divided by 2434mm (8 feet) multipled by 6096mm (20 feet) = 25.45mm lens

The first example can arguably be covered with a standard 9mm-22mm varifocal lens that you find on many cameras nowadays. The second example, however, cannot be covered by a 9mm-22mm lens unless you are willing to sacrifice PPF or move the camera closer to the target. Both are viable options, but a sacrifice is being made somewhere for this "modest" difference.

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The first example can arguably be covered with a standard 9mm-22mm varifocal lens that you find on many cameras nowadays. The second example, however, cannot be covered by a 9mm-22mm lens unless you are willing to sacrifice PPF or move the camera closer to the target.

Your example is real but an edge case. We are not saying it makes no difference just that as you quote us, '"variances among imager sizes tend to be modest".

So, if you are attempting to capture a person walking into an entry way and need an 8 foot vertical height and the distance is 20 feet away, the calculation looks like this...

In 2019, the calculation should be done via software, whether it is our IPVM Camera Calculator or other design software. For example, that's why we have 10,000+ camera models in our calculator so you don't have to run any manual calculations, you just pick your model and see if it covers it on the map.

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No doubt. Your camera tool is definitely more sophisticated and simpler than my crude back of the napkin sort of method. I have used the tool you and your team have developed and I do like it.

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True. But your calculator doesn't work indoors and that's where 75% of my cameras are installed. It's definitely still worth knowing how to calculate it yourself. Besides, we're supposed to be experts right? Any DIYer can find one of hundreds or thousands of online FoV calculators. It's up to us professionals to know understand what it means and how to apply it correctly. Sure tools can be great timesavers, but my employees aren't allowed to use them until they can make the calculations by hand and demonstrate they actually understand them.

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But your calculator doesn't work indoors and that's where 75% of my cameras are installed.

Our calculator works indoors. If you don't want the map at all, that's fine, just choose blank screen. You can toggle as shown below:

And if you want booth indoors and outdoors on a map, add a floorplan.

It's definitely still worth knowing how to calculate it yourself.

Agreed, it's worth knowing that's why we teach this in our class.

Sure tools can be great timesavers, but my employees aren't allowed to use them until they can make the calculations by hand and demonstrate they actually understand them.

Ok, good but it would be very inefficient to manually calculate these metrics each time. And you also run the risk it being wrong since these equations to calculate FoV abstractly often do not match manufacturer specifications.

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1/2.8" imager

9.07mm divided by 2434mm (8 feet) multipled by 6096mm (20 feet) = 22.71mm lens

1/2.5" imager

10.16mm divided by 2434mm (8 feet) multipled by 6096mm (20 feet) = 25.45mm lens

btw, you can’t just convert 1/2.8” to mm and use that in calculations. for a variety of reasons.

see: Easy Question: What Is The Size In Mm Of A 1/3" Sensor?

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What I don't see in the lens calculators is an area of coverage. If the camera mounting to the side of the building is suppoed to view the parking lot, how much of the parking lot is within the field of view? Vertical and horizantal measurements are both important.

More so when we do fence line cameras. Example - 5MP camera is mounted at 12' off the ground, the bottom of the camera view is 50' from the pole, if the camera is in corridor mode, and I need 60 ppf, how far out will the camera provide that resolution given the appropriate lens, and what downward angle do I mount the camera to provide the correct view?

I know the installers can just look at the view and adjust accordingly. But I need to do the calculations ahead of time to make sure that I pick the proper resolution camera and size lens to provide the required field of view.

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What calculators are you using? It's in every one I've ever seen.

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The Camera Calculator offers Blind Spot calculation, based on camera height (how high off the ground it is installed) and scene height (the top of the camera's calculated field of view):

Enabling Blind Spots on Map

Blind spots are defaulted off but can be toggled on for all cameras. The default camera height is set to 10 feet or ~3 meters. Scene height (top of the camera field of view) is also set to 10 feet by default.

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ok, i’m confused. isn’t the tilt angle the angle between the imager plane and the ground?

here the tilt is 0, but the camera seems to be pointing down:

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The Calculator defines tilt as the top edge of the FoV relative to the horizon/horizontal line at the height of the camera.

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The Calculator defines tilt as the top edge of the FoV relative to the horizon/horizontal line at the height of the camera.

ok, but as a practical matter, how is one to use this information to mount their camera?

in the field i can deduce the plane on which the imager lies, and using an angle finder make precise adjustments from the perpendicular, with the assumption that level is 0 degree tilt.

how does one know how much to angle the camera using your tilt value?

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The Calculator defines tilt as the top edge of the FoV relative to the horizon/horizontal line at the height of the camera.

not to belabor the point Sean, but just trying to understand, are you saying that what the calculator considers the “tilt angle” is different than the standard working definition?

as an example, the recent hik dual camera test says:

Using 40 pixels between the pupils, the lowest recommended setting, performance was optimal at downtilt angles ranging from ~6° to ~33°. No faces were missed using these settings in evenly lit scenes.

is the 6 degree downtilt from that article something that can be plugged into the calculator directly or?

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HFoV (Horizontal Field Of View): The width of the scene at a specific point, e.g. 100' wide at 50' distance. HFoV is frequently simply referred to as FoV.

AoV (Angle Of View): The angle, measured in degrees, of the camera's coverage area.

to be clear, both of these refer to horizontal measurements, the AoV that you reference is actually HAoV, and there is a vertical and diagonal AoV as well just like in FoVs.

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In my use case, FoV is critical. This reading assignment was very helpful.

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