Changing Camera resolution but keep the same resolution gate

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I do some projects where it is originally made at a 9 x 16 aspect ratio. Later down the road I need to make a 16 x 9 aspect ratio version of the spot. I use the same camera, but rotate my comp for the front, but when the product is revealed at the end, I cannot use the same camera to keep the composition.

This hasn't been a problem because I had been doing the product in Maya up till now. Under the camera properties in Maya, under Film Back, there is a drop down called "Fit resolution gate". If I change it to "Vertical" and flip my cameras aspect ratio, it will keep the same framing of the product (just wider now/more revealed on the sides), and I am able to use one render for two spots. I can not find any option like that in Houdini.

I hope this made sense, I appreciate you taking time to read and help if you can. Thanks.

Edit: I think I was able to get it to work through exporting it to Maya and re importing it as an fbx. Here is a visual of what I mean
Edited by animationalex - Jan. 19, 2021 18:16:49

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you can multiply Aperture on the camera by (16/9)^2
so if your aperture was 24 it will be 24*pow(16/9,2)
Tomas Slancik
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Method Studios, NY
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tamte
you can multiply Aperture on the camera by (16/9)^2
so if your aperture was 24 it will be 24*pow(16/9,2)

Hi Tomas, could you explain the math, I am trying to do the same thing but it is with different ratio.
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zjie
Hi Tomas, could you explain the math
so from the original problem
there is an image with certain known width(w) height(h) and horizontal aperture(ha)

houdini computes vertical aperture(va) like this:
va = ha * h / w

then we need to compute new horizontal aperture ha2 for camera with flipped h and w and the same vertical aperture:

using the same equation from before for new camera it would be:
va2 = ha2 * h2 / w2

and substituting for what we know that:
h2 = w
w2 = h
va2 = va

we get:
va2 = ha2 * h2 / w2
va = ha2 * w / h
ha2 = va * h / w

and since we know that va = ha * h / w
that gives us:
ha2 = ha * h*h / w*w

and hence:
ha2 = ha * (h/w)^2
Edited by tamte - April 27, 2022 13:58:40
Tomas Slancik
FX Supervisor
Method Studios, NY
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