I can confirm the observation of Rayman29.
If you have some knowledge of real world photography, focal lenght and aspect ratios you should immediately notice that whatever happens in the DS viewport at an aspect ratio of 10:1 is not in any way based on real world camera values at a focal lenght of 50mm.
In a realistic simulation there should be no interaction between aspect ratio and focal lenght at all.
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I also set focual lenght to 50mm and the render aspect ratio to 10:1.
Focus is set on the cube front surface.
The cube in the scene AND the wireframe ground plane are completly distorted in the DS viewport.
If focal lenght is at 50mm there should be NO DISTORTION what so ever.
In this specific example the lower side of the cube seems to be smaller than the upper side.
There is NO logical reason why this should happen at a focal lenght of 50mm.
In the OctaneRender viewport you can also see that this distortion is affecting the OctaneRender plugin as well.
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So I believe it may be as Rayman29 explained.
For some reason the aspect ratio is distorting the focal lenght in a way that the viewport is showing an image with a much lower focal lenght.
As pointed out by Rayman29 the actual (!) focal lenght of the viewport seems to be around 5mm or even lower.
At a focal lenght of around 8mm also with real world camera lenses you can observe such extreme distortions of the image.
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Admited an aspect ratio of 10:1 is very well unusual.
It would be interesting to do further testing.
Is the “apsect ratio bug” behaving in a linear way?
Is there some kind of treshold after which extreme aspect ratio values cause unrealistic distortions by affecting the focal lenght.
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