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Message: <blockquote data-quote="RJM" data-source="post: 1642482" data-attributes="member: 66340">As for #1, actually the bottom of Nikons own <a href="http://www.nikon.com/products/sportoptics/how_to/guide/fieldscopes/choosing/choosing_04.htm" target="_blank">website </a>does a pretty good job of showing the relative field size of a fixed mag widefield eyepiece and a zoom at the same magnification and explaning why you should pick one over the other. Perhaps one birdwidth more field makes a big difference for you, but it doesn't for me. As for #2, I think you are confusing image brightness with the ability to see detail/make an ID in low light. Image brightness is determined by eyepiece exit pupil diameter BUT is also constrained by the eye pupil diameter which during sunrise/sun up seldom exceeds 3-2mm, expanding to perhaps 4-5mm at sundown/twilight. The optics OEMs put out a specification called Relative Brightness (eyepiece exit pupil diameter squared) to rank optics but it is relatively useless. On the otherhand, the ability to see detail/make an ID in low light is strictly a function of magnification and aperture and the OEMs do have a very useful specification for this called the Twilight Factor (sqrt(mag x aperture)). Basically means a 40x50mm optic will reveal more easier than a 27x50 optic under identical light. What should be obvious is a zoom is capable of both giving the brightest image/widest true field when needed or revealing the most detail as necessary when compared to the 27x Wide.  Hope this helps,Rick</blockquote>

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