I'm trying to set up a home video studio on the cheap. Largely a video-podcast format, around a table, to be live streamed on twitch

Is there a way I can preview / frame shots physically, at different Field of Views so that I can plan purchases, of webcams, cameras or lenses?


4 Answers 4


New version

Thanks xiota and Carsten S!

I. Define what is the sensor size you are going to use. Let's say you will be using a full-frame camera. (36x24mm)

II. Take a cardboard a bit larger than 10 times that, 46x36cm and make a hole in it, of 36x24cm. We are making a frame 10 times bigger than the sensor. Instead of using mm we are using cm.

III. Put an assistant sitting in the correct place and use the cardboard to plan your framing.

When you like a framing, measure the distance from the cardboard to your eye. Do not poke your eye :o)

IV. The distance in cm (B) from the board to your eye will be the focal length in mm of the lens you need. For example, if the distance is 50cm, the lens you need is 50mm.

Some notes.

If you make the board 10x of the measures of the sensor you will be using you do not need to make any conversion. FC, DX or 2/3 or whatever.

If you do not know yet what camera you will be using you can make a "full-frame" board and then apply a crop factor.

If the camera you are using does not declare the "mm" of the lens or sensor size, but only the field of view, like a webcam, use the "old version" method.

Old version

Take a cardboard of 40x30 cm and make a hole in it, of 30x20 cm. You can scale this down to half or something and keep the proportions. But is will be more comfortable working with bigger dimensions (and more accurate).

Put an assistant sitting in the correct place and use the cardboard to plan your framing.

When you like a framing, measure the distance from the cardboard to your eye. Do not poke your eye :o)

Now let's use those numbers.

A) Half the longest side of your framing cardboard (interior)

B) Distance to your eye.

C) Put those values on an angle calculator like this one:


Where the base will be B and the height will be A (Altura in Spanish n_n)

You will get the angle C. As this is just half the angle of the real field of view of your cardboard, multiply this for two. (Example below)

D) Take that number and play with this simulator



A) My cardboard's interior longest side is 30cm. Half of it is 15cm.

B) The distance to my eye is 30cm

C) The angle on the calculator is 26.5° multiplied by 2 is 53°

D) On the field of view calculator on a DX camera, 53° is around a 28mm lens.

Keep in mind that the mm and the angle of view is dependant on the sensor size. Some webcam cameras will give you the viewing angle instead of an mm lens equivalent.

Original image: https://pixabay.com/es/photos/chica-joven-estudiante-sentado-3718526/

  • 3
    \$\begingroup\$ Oh hey, now I know why purportedly movie makers in the 50s would hold out their arms and make the opposing sides of a rectangle with the squared thumb and index finger to get an idea of what the picture would look like when scouting out a location. \$\endgroup\$
    – Michael
    Feb 25, 2020 at 3:03
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    \$\begingroup\$ I understand that this works, but using trigonometry to convert a proportion to an angle and back again seems overkill to me. You can also get the focal length as B * sensor width / 2A. (Assuming that the focal point of the length will be where your eyes are now.) So in your example, the focal length would be the sensor width, 24mm for DX. \$\endgroup\$
    – Carsten S
    Feb 25, 2020 at 11:33
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    \$\begingroup\$ @MikeBrockington, no, they don't. \$\endgroup\$
    – Carsten S
    Feb 25, 2020 at 12:48
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    \$\begingroup\$ Use a card with a cut out the same size as the camera sensor. Distance from eye is focal length needed. Or can use crop factor for larger frame. No need for trigonometry calculations. \$\endgroup\$
    – xiota
    Feb 25, 2020 at 16:32
  • \$\begingroup\$ @MikeBrockington about the angles, the triangle must be a 90° triangle or this will not work. That is why I divided the triangle in the first place. Use the calculator I posted and try using A with double the length and you will see that gives you a different angle. \$\endgroup\$
    – Rafael
    Feb 25, 2020 at 18:34

Yes. Use a camera with a zoom lens with enough zoom range to cover all/most of the lens focal lengths you are considering, and take several sample shots or videos at different focal lengths to previsualize (Wikipedia) your scene.

If you don't have a camera and/or zoom lens to do that, depending on your location, you can rent gear to do the previsualization, or even rent the actual gear you are considering buying, before you commit to a purchase.

  • 2
    \$\begingroup\$ @Stan thanks, I normally try not to use unclear jargon. Don't know why I so casually threw it in this time. Edited to use full words, and a link to WP's article. =) \$\endgroup\$
    – scottbb
    Feb 24, 2020 at 15:14

You can download a phone app that will simulate various focal lengths. For example, Artist's Viewfinder on iOS.


This website lists a range of camera- and lens-simulators which might be helpful.

Some of the simulators are listed below:


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