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Message: <blockquote data-quote="613Orm" data-source="post: 3218555" data-attributes="member: 107876">I am grateful for all suggestions.  I think maybe I did not express the concept very well. The concept is that I first look at the object positioned at the center of the field (where one would expect it to appear sharpest), then I move the object towards the side of the field (about halfway to the edge). However, I still point my eyesight towards the object. This would mean that if I had any defect in the center of my vision it would still affect the view. Astigmatism combined with binocular's astigmatism could explain why it would appear differently sharp. However, if it can also be noticed by someone that does not suffer from astigmatism then it should be due to something else, possibly a difference in contrast (rather than resolution) towards the periphery. I do not think this concept is very far off from what a binocular is designed for. If it was meant that all objects always have to be positioned in the center then this ever ongoing quest for "edge to edge sharpness" in binocular design is unnecessary. But I think it makes sense that you are able to follow a bird with your eyes when it moves through the field of view. However, personally, I find this more useful in a spotting scope where you may let the bird walk around in the field without redirecting your scope. With a binocular it is certainly more common that one redirects it to follow the birds movements. It was when not doing so that I run into this effect of different sharpness (or contrast) over the field, I followed the bird with my eye (which for a static object is the same as moving the binocular slightly sideways (which I then tested on tree bark, and signs with black text on white).</blockquote>

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