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Message: <blockquote data-quote="Huang_Lingyun" data-source="post: 1299399" data-attributes="member: 69849">Regarding the image quality from the center to the edge of Field Of View, in optical system design, it is quite difficult to correct the imaging tolerance  for the outter FOV from 75% to the edge.  So If we want a flat FOV, sometime we have to reduce the FOV.For exsample, some 8X42 binoculars only have a FOV of 6 degrees.Otherwise, we must design a very complex eyepieces optical elements or use the aspherical technology, which you can find on Minox binoculars, Docter binocualrs and Bushnell E2. But these will highly increase the cost.By the way, under my testing, Hawke Frontier ED objective FOV of 8X42 is 8.12° and 10X42 is 6.5°( FOV at eyes side: 8.12X8°=65°, 10X6.5°=65°, Wide Angle),and the resolution should be under 4".  But the imaging quality in almost 1° marginal area is not good. Even I need to newly focus ( adjust diopter) when you move the target from the edge to the center of FOV. But imaging quality in the main area of FOV is very good, true clarity, neutral, with high contrast. and its double hardcases including inner hardcase and external hardcase are convenient. At the same time, its neckstrap is comfortable.</blockquote>