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Message: <blockquote data-quote="looksharp65" data-source="post: 3621533" data-attributes="member: 83771">You're welcome!True, and I actually didn't think of the added complication of the resulting base up/down effect due to rotation when IPD is adjusted.Excuse me, but I'm lost here. I understand that your main goal is to increase the resulting true field of view by reducing the common area seen with both eyes. Your analysis that the image of an object will be seen closer to the medial parts of the respective FOV's is correct. It is also correct that this requires added convergence, but I'm puzzled why you seem to consider this an advantage. A traditional porro does almost exactly this when used at finite distance.Once the right and left image of the object gets too close to the medial edge of the FOV, visual discomfort appears. This may be the result of either excessive convergence strain or difficulty to center the object in the narrow almond-shaped common area. That's why IPD adjustment helps. That's also why wide FOV's make traditional porros reasonably useful even at fairly close distance.A traditional porro's best asset is the wide spacing between the objectives, where the added parallax will enhance the 3D perception.It is not the convergence of the eyes that enhance the 3D perception.And you got the effect right - the light bends towards the prism base in your Fig. 2(a).If you put base in prisms like in that figure, or for that matter one prism (makes no difference if you spread the prism power on one or two prisms), the eyes must diverge to not deliver a double-image. Re the Fig. 3(b) regardless of whether it's central or peripheral light rays, when they converge like that, they don't come from the same object, i.e. diplopia will occur.Regards,Lars</blockquote>

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