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Message: <blockquote data-quote="FrankD" data-source="post: 1615870" data-attributes="member: 18544">Mak,The 5% comment you mentioned I think is in reference to Henry Link. He mentioned in one of his posts at some point over the last year or two that he was able to notice a 5% difference in apparent image brightness.As for measuring the sweet spot, I am sure folks do it. In fact I know folks do it as I remember some comments from Henry, in particular, where he measured the percentage of field of view relatively free from distortion in the Atlas Optics binoculars. I would think that in order to do so you would need some type of chart similar to the USAF resolution chart but with some type of percentages listed across the image. I seem to remember seeing something of this nature when I was trying to hunt down a good, relatively inexpensive USAF resolution chart.As for not having a subjective opinion on the issue, that is difficult. Many times a subjective opinion overrides objective measurements. For example, if an image "appears" to have a wide sweet spot because the degree and severity of distortion is minimal and gradual the does it really matter if the sweet spot actually measures quite small?Just something to think about.</blockquote>