Posted 04 November 2010 - 12:33 PM
This is a very long and winding thread, so I thought I’d summarize the Nikon 18x70 measures to date and compare to the single most comparable binocular, the Fujinon 16x70.
The Nikon 18x70 reached exactly the same on-axis resolution standard as the Fujinon 16x70. By nature of it’s higher power, the Nikon should be able to reach proportionally smaller resolution and did so almost exactly in step with expectations. The 18x70 resolved 4.0" and the Fujinon resolved 4.5", one step apart on the resolution charts and almost exactly equal to the difference in magnification. Therefore the resolution of these two can be considered equal.
The Nikon, by nature of the slightly larger image scale due to higher magnification, could see some smaller objects easier and could see some closer pairs of stars.
The TFOV is equal, both having 4.0°.
The Fujinon 16x70 has a sharper aberration free field of view than the Nikon 18x70. Measured to the same standard, the Nikon has only 3.0° fov with equal sharpness to the Fujinon 3.8° fov. That is based on the measure that the Fujinon has 95% of the field equally sharp to the central 70% of the field in the Nikon. The predominant aberration that causes the loss of field in the Nikon is curvature. The Fujinon sharp field of view exceeds that of the Nikon by a very large margin.
The Fujinon fully illuminated field of view of 50% exceeds that of the Nikon which has only 41% fully illuminated fov.
The Nikon weighs 6 ounces less than the Fujinon. However I would not consider either of these hand-holdable binoculars, so this has little benefit for a mounted binocular.
The Nikon does have smaller eyepieces and while that made no difference to me, some may find that a benefit if nose clearance happens to be an issue.
The Nikon, once the hard plastic eyecups are replaced with a much lower profile round rubber eyecup that can be used with eyeglasses, provides 2mm more eye relief than the Fujinon, 11mm usable eyerelief for the Nikon vs 9mm for the Fujinon. In normal use with eye glasses, without pressing up tight against the eyecups, I can see about 95% of the field of view in the Fujinon. Even with the Nikon low profile rubber eyecup folded down, eye relief is still a bit short for eyeglasses, so some of the Nikon fov is lost to view.
False color, both on-axis and off-axis, is identical in both and is easily seen on the moon and Jupiter.
Curvature in the Nikon at 50% out is about equal to the Fujinon. However by 70% out from center, the Nikon has 3x the curvature of the Fujinon. It continues at 3x the Fujinon out to the field edge.
The Nikon 18x70 has considerable globe or rolling ball effect. It is noticable when panning in daylight. It is far more noticable when panning at night. It is not noticable when not panning. The Fujinon 16x70 appears to have no globe effect.
The Fujinon twice measured the same limiting magnitude (LM) on-axis as the Nikon, different nights, similar conditions. Both times both binoculars saw an on-axis limiting magnitude of mag 10.7 under a mag 5.0-5.1 sky. I would expect nearly a half magnitude improvement under skies a half magnitude darker. By nature of its higher magnification, as is evident in many test results, under any sky condition, the 18x Nikon should be able to see fainter stars than the 16x Fujinon, at least 0.15mag fainter. This expected difference is entirely magnification dependant. It is possible that further testing will show the Nikon reaches its expected LM premium gain over the Fujinon, but so far it has not.
The Fujinon performed considerably better in off-axis LM. Both binoculars have a 4° fov and therefore have 2° off-axis from center to edge. The Fujinon could still see mag 10.25 stars at 60% off-axis or 1.2° out from center. The Nikon could not see any better than mag 10.0 at 50% out, or 1.0° off-axis from center. That degree of difference in magnitude seen was maintained out to the fov extent. Not only does the Fujinon record fainter stars off-axis by a fair margin, but it can see those fainter stars further out.
More tiny craters were seen on the Moon using the Nikon 18x70 than with the Fujinon 16x70. But there was no noticeable improvement in contrast or resolved image other than that gained by the slight increase in image scale. For objects that were large enough to view at both scales, I could not say that I was able to see more detail in the Nikons.
So far, I have not seen any diffuse extended object in the Nikon that I did not also see in the Fujinon.