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Message: <blockquote data-quote="RJM" data-source="post: 1753885" data-attributes="member: 66340">I think it is important not to obsess over testing small binocular optics UNLESS there is something obviously not pleasing about the images and you want to determine the cause.  Small binocular operating magnification is just too low at infinity focus for MEANINGFUL differences to reveal themselves. Without special tools/techniques optical aberrations will be difficult to quantify and can be overly influenced by the user's own eye defects due to large exit pupils. Only the most obvious aberrations of distortion, curvature, and on-axis chromatism will be easy to see and these show up in ALL binoculars to varying degrees.  In the end, mechanical and ergonomic differences actually have a greater influence on how you will perceive a small binocular than the optics. That said, nothing wrong with verifying the published specifications as these always seem to be off, especially weight, FoV, and CLEAR aperture. Focus speed is also important but seldom reported spec for the birder.  The basic optical tests you should perform are first to check for collimation and image alignment. Then inspect the AR lens coatings for defects and then for quality by observing how much of your face can be seen when reflected in the lenses. Uncoated surfaces can be seen with a light source as reflected "white" lights. Clear aperture of each objective can be measured by shining a bright light through an eyepiece from ~1m distance and directly measuring the projected circle on a white wall. Make sure the binocular is focused at infinity for an accurate reading. If you cannot achieve perfectly round and defined circles with a diameter equal to the spec then it has an obstruction somewhere in the light path. For optical tests, I prefer the test targets provided by Mother Nature, i.e., the Full Moon and star fields. Mount the binocular on a tripod and use the Full Moon diameter (~0.5°) to get a rough measure of FoV and sharpness across the field. Also move it just outside the FoV to look for glare issues.  On a very clear night, any on-axis chromatism will be visable along the Moon's edge as well as the tint of the optics. Then look through each ocular independently and notice how stars come to focus at the center and then towards edge of field to determine if curvature is the dominant aberration. If you can choose star sets of know separation then you may get a decent estimate of how far from the edge image breakdown occurs.  For distortions, you just need to point the binocular anywhere you see straight lines. Henry came up with a brilliant visual tool if you can find a clear silicon suction cup to stick on a window near an edge. In either case, any distortion seen will be meaningless unless you can compare to another binocular. I feel these basic tests reveal much more about the binocular than any attempts with a USAF resolution chart. have fun,Rick</blockquote>

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