Calculating Subject Proportion

[ConnorCapetillo]

I'm attempting to film a practical of a company leader and need some help with calculating the size of the various layers.

What we're trying to accomplish is this: a camera will track a half moon/crescent shape. In front of it are about four layers that when combined make up our logo. As the camera moves from the side/start position to the middle/end position the layers line up and form the end image.

my question is this: since the layers are different lengths away from the camera/lens how do I calculate how large to print each layer. I assume the layers closest to the camera have to be proportionally smaller than the back layers, correct?

any help would be appreciated.

Thanks!

 

[JWerner]

Assuming your layers are parallel to the camera's film plane at the end position, and the layers are centered in the camera view, it should be easy using some math apps.

Start with the layer that's farthest from the camera and print it as large as you'll need. Measure the layer from top to bottom, then divide by 2.

Take that layer to the set and position it as needed, then set up the camera to get the correct view. Measure the distance from the camera's film plane to the layer, using the same units used to measure the layer.

Then you can google a "right triangle angle side calculator". Enter the size of the layer divided by 2 as side a in the calculator, and the camera distance as side b. Calculate the angle A.

By varying side b (the distance from the camera to a layer) and using angle A, you can calculate the sizes of the other layers as side a multiplied by 2. Varying the distance also lets you take depth of field into account.

This should work if you want all of the layers to be the same size on screen. It may take some adjustment on set, and lens distortion could be a factor.

 

[David.rhsc]

This sounds like reading up a little on forced perspective might help you out.

Alternatively, just set up your camera and use rough cardboard shapes or something to mock up a quick test. Adjust the distances and such to see how the sizes relate.

 

[ConnorCapetillo]

Assuming your layers are parallel to the camera's film plane at the end position, and the layers are centered in the camera view, it should be easy using some math apps.

Start with the layer that's farthest from the camera and print it as large as you'll need. Measure the layer from top to bottom, then divide by 2.

Take that layer to the set and position it as needed, then set up the camera to get the correct view. Measure the distance from the camera's film plane to the layer, using the same units used to measure the layer.

Then you can google a "right triangle angle side calculator". Enter the size of the layer divided by 2 as side a in the calculator, and the camera distance as side b. Calculate the angle A.

By varying side b (the distance from the camera to a layer) and using angle A, you can calculate the sizes of the other layers as side a multiplied by 2. Varying the distance also lets you take depth of field into account.

This should work if you want all of the layers to be the same size on screen. It may take some adjustment on set, and lens distortion could be a factor.

Thank you so much JWerner, that is exactly what we were looking for!