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Message: <blockquote data-quote="mak" data-source="post: 1311616" data-attributes="member: 774">Kevin.Stray light can be measured in fact some manufacturers have stray light measurements.  They would not publish them as they wouldn't for the total light transmission, but some results totally contradict many of the postings on bird forum.  That is the difference between subjective and measureable, however under the circumstances that no published figures are available, you are correct, it has to be a hands on approach.One of the criteria mentioned is "Sweet Spot" what is that?  If we are talking about the relationship between FOV and the Zone.  This can be measured.Zone = FOV / Sq root 2.Again, there are other considerations to bear in mind for the Zone (or is this the so called sweet spot) optics design for one.  But it is measureablemak</blockquote>