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could somebody explain how orthographic scale is calculated in Blender? I am trying to match an orthographic view that I get from another software with that of Blender, but I am not able. Camera gets in the correct position but the zoom level is wrong.

Thanks, byte

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The Orthographic Scale factor represent the maximum dimension (in scene units) of the portion of space captured from the camera.

So a scale of 1, means that a square plane whose size is 1, would perfectly fit the camera's view in the mayor dimension (for the default 1920x1080, the wideness).

If you double the scale, you'll get half dimension (1:2 scale) because the way it's mean to work like the traditional scale map. Maybe it's even easier to think in these therms:

The scale of a map is the ratio of a distance on the map to the corresponding distance on the ground.

About your specific problem, I think I would suggest the following workflow:

  • Match the camera's and reference image proportions and import as background image
  • Align the view
  • Tweak the scale factor till you are satisfied
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    $\begingroup$ Please don't add "thank you" as an answer. Instead, accept the answer that you found most helpful. - From Review $\endgroup$
    – Ray Mairlot
    Commented May 16, 2016 at 10:48
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    $\begingroup$ Late arrival, but some clarification. the orthographic camera scale is in Blender Units, not scene units. I wanted an ortho camera to be exactly 12 inches, so I switched to blender units, made a plane 1x1 unit, switched back to imperial, and then set the dimensions to 12x12 inches. That gave me a scale of .305, which I set as the camera's orthographic scale. This technique should get you a lot closer than manual adjustment. $\endgroup$
    – Arcandio
    Commented May 20, 2022 at 20:19
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Prerequisite:

If we define the ortho-camera's width to be the major dimension (Sensor Fit = Horizontal), then the width of the ortho-camera's viewport is set to 1 blender unit (in camera-space). Otherwise the height's viewport is set to 1 blender unit (in camera-space).

enter image description here

Definition:

The orthographic scale now results from the ratio of the above defined blender unit (in camera space) to 1 blender unit (in global space).

Basic Example:

By using elemental trigonometric maths a unit square in global space would exactly fit in the camera's viewport (width), if the value of the orthographic scale is exactly √2 = 1.41... .

enter image description here

enter image description here

So if you double this value to 2*√2 then 2 unit squares will exactly fit in the camera's viewport width (while the viewports camera width still remains 1 blender unit in camera space). enter image description here

Consequences:

With the knowledge, that the ortho camera's width is always 1 blender unit, we can only vary the camera's visible viewport content by

  1. changing the orthographic scale
  2. and/or changing the resolution of the camera's viewport width and height

With those two main parameters it is possible to adjust the ortho camera exactly to your specific needs. enter image description here

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