As I continue to build out the photographic knowledge base on the site with articles like Understanding Neutral Density Filter Names and Numbers, and Understanding Aperture, I thought I’d write a quick post about how to calculate field of view for a photographic lens.  Lenses are usually described by their focal length, expressed in mm, but how does this translate to field of view?

If you read lens specifications (yes, I’m that kind of guy) on manufacturer’s websites, they’ll often quote the field of view (F.O.V) of a lens as well as the focal length.  When they do this in photographic terms, they’re talking about horizontal field of view in degrees, and whilst any lens will also have both a vertical and a diagonal field of view, they are rarely talked about in relation to photographic lenses.

The larger the field of view, the wider the lens is and the more of a scene you are going to see with your camera.  Telephoto and super telephoto lenses have very small fields of view, just a few degrees, so they aren’t able to see very much of the scene in front of them, although the compensating virtue is that what they do see, is much larger in the frame.  A wide angle lens for landscape photography has a very small focal length, and therefore a large field of view that lets you record broad landscapes in a single shot.

Equation For Calculating Angle of View

Simple trigonometry will give us the equation:

Angle of view (in degrees) = 2 ArcTan( sensor width / (2 X focal length)) * (180/π)

Note: If your calculator is working in radians, you need the (180/π) part at the end.  if your calculator is working in degrees, you do not need that bit! If you aren’t sure… it will become pretty obvious when you run the equation as results will be wildly wrong.

Equation for Calculating Linear Field of View

As well as calculating the angle of view, we can also use the same trigonometry to calculate the field of view as a linear measurement, as long as you know the distance to your subject, or, if you know the size of your subject and the focal length you are going to use, it could tell you how far away from it you need to be to get it to fill the frame. The units of measurement will be constant in the equation, so if you use metres as your distance to subject, the linear field of view will also be in metres.

Linear field of view = 2 (Tan (Angle of view/2) X Distance to Subject) 

Common Focal Lengths and Their Corresponding FOVs

Since the equation for field of view contains the sensor width, which determines the crop factor of a lens, this is another way to see the effect that the crop factor of a camera has on an image. The smaller the sensor, the larger the crop factor, and the smaller the field of view for a given focal length. Below I have included data for full frame field of view, as well as the three most common digital crop factors. If you want to learn more about crop factor, you can read my tutorial: How To Calculate a Camera’s Crop Factor.

If you want to use the field of view equation on this page to calculate the field of view for a sensor size other than the four that have been provided, you’ll need to refer to this post to get the sensor width to plug into the equation: Common Digital Sensor Sizes and Crop Factors.

Full frame 35mm (36mm sensor width)

Focal Length Field of VIew
15mm (Fisheye) 180.0
11mm 117.1
14mm 104.3
16mm 96.7
24mm 73.7
35mm 54.4
50mm 39.6
85mm 23.9
100mm 20.4
150mm 13.7
200mm 10.3
300mm 6.9
400mm 5.2
500mm 4.1
600mm 3.4
800mm 2.6
1000mm 2.1
1200mm 1.7

Nikon DX APS-C (1.5x) (23.6mm sensor width)

Focal length (35mm) Equivalent focal length Field of View
11mm 16.5 94.0
14mm 21 80.3
16mm 24 72.8
24mm 36 52.4
35mm 52.5 37.3
50mm 75 26.6
85mm 127.5 15.8
100mm 150 13.5
150mm 225 9.0
200mm 300 6.8
300mm 450 4.5
400mm 600 3.4
500mm 750 2.7
600mm 900 2.3
800mm 1200 1.7
1000mm 1500 1.4
1200mm 1800 1.1


Canon APS-C (1.6x) (22.5mm sensor width)

It must be noted here that Canon has actually used difference sensor sizes for their APS-C cameras over the years. Since the sensor dimension does affect the field of view, this should be taken into account in order to be 100% accurate. For the data table below I have chosen to use the sensor width of 22.5mm because this is the one that Canon seem to have stuck with for their own calculations, and it is also the dimension that gives exactly a 1.6x crop factor. Whilst they do have 22.3mm and 22.4mm sensor widths on the market as well, this minuscule difference would not actually make any noticeable difference to your images, but if you ran your own calculations for your own camera and found they did not match my numbers, this will be the cause of the difference. It was the source of some head scratching for me when I was figuring all this out myself!

Focal length (35mm) Equivalent focal length Field of View
11mm 17.6 91.3
14mm 22.4 77.6
16mm 25.6 70.2
24mm 38.4 50.2
35mm 56 35.6
50mm 80 25.4
85mm 136 15.1
100mm 160 12.8
150mm 240 8.6
200mm 320 6.4
300mm 480 4.3
400mm 640 3.2
500mm 800 2.6
600mm 960 2.1
800mm 1280 1.6
1000mm 1600 1.3
1200mm 1920 1.1

Micro Four Thirds (2x) (22.3mm sensor width)

Focal length (35mm) Equivalent focal length Field of View
11mm 22 78.6
14mm 28 65.5
16mm 32 58.7
24mm 48 41.1
35mm 70 28.8
50mm 100 20.4
85mm 170 12.1
100mm 200 10.3
150mm 300 6.9
200mm 400 5.2
300mm 600 3.4
400mm 800 2.6
500mm 1000 2.1
600mm 1200 1.7
800mm 1600 1.3
1000mm 2000 1.0
1200mm 2400 0.9

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