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Nikon 18x70 measures

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#151 Fomalhaut

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Posted 03 November 2010 - 02:34 PM

How in the world can you even suggest to relate limiting magnitude across the field of view to Apparent field of view. I find no practical application to this.

Frankly, I can't imagine that anyone could care less about the degrees of Apparent field at which these measures occur. The fact is, I'm comparing real fields of view and the percentage of that field that the manufacturer has optimized. edz


EdZ,

Yes, that's the problem. And I compare apparent light cones of the same opening angle (aperture angle, beam width? Choose the best word...), and here the Nikon is just about where the Fujinon is... The other (your) way round a binocular with a wider field is either punished for this or alternatively for its higher magnification...
Your way a 70mm binocular with a 45 deg AFOV would almost automatically prevail even over the Fujinons :crazy:

Chris

#152 EdZ

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Posted 03 November 2010 - 02:38 PM

The other (your) way round a binocular with a wider field is either punished for this or alternatively for its higher magnification...



No, I do not punish the binocular. The manufacturer did that by not optimizing the design. I just report the test results.

You can find numerous examples in all my published data where a wider field instrument preformed much better than a narrower instrument in a comparable set. The Nikon fails to do that.

edz

#153 94bamf

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Posted 03 November 2010 - 02:44 PM

How in the world can you even suggest to relate limiting magnitude across the field of view to Apparent field of view. I find no practical application to this.

Frankly, I can't imagine that anyone could care less about the degrees of Apparent field at which these measures occur. The fact is, I'm comparing real fields of view and the percentage of that field that the manufacturer has optimized. edz


EdZ,

Yes, that's the problem. And I compare apparent light cones of the same opening angle (aperture angle, beam width? Choose the best word...), and here the Nikon is just about where the Fujinon is... The other (your) way round a binocular with a wider field is either punished for this or alternatively for its higher magnification...
Your way a binocular with a 30 deg AFOV would prevail even over the Fujinon :crazy:

Chris


You act like the people reading the reviews don't know the AFOV of the binoculars being tested. It is not like Edz hides this info. I want to know the percentage of FOV that provides good views based on the known AFOV of the binocular. If you don't know the AFOV of the bins being tested and you don't take that into consideration with the percentages, well, your really not paying attention anyway.. Just my 2 cents..

Ken

#154 Fomalhaut

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Posted 03 November 2010 - 02:44 PM

EdZ,

I do not agree with you. I just enjoy the concentric part of the Nikon's field which is of the apparent size of the Fujinon's entire one and consider what is overlapping (and where most of the aberrations occur) a result of higher magnification and hence just for free...

Chris

#155 GlennLeDrew

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Posted 03 November 2010 - 06:09 PM

While the use of stellar limiting magnitude does go some way toward providing some measure of off-axis illumination, we are all aware of its weakness, namely the sensitivity to aberration-induced loss as the point source becomes spread out. A system which suffers worse blurring will perforce rate more poorly. This is much more an indicator of image definition than illumination.

A better indicator of illumination characteristics would be provided by surface brightness measurements. This has the advantage of making use of a uniformly-illuminated target filling the full field, the continuous flux therefrom completely negating the blurring introduced by optical aberrations which so profoundly impact on point sources.

I really should cobble up a 'test bed' and give this a whirl...

#156 Fomalhaut

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Posted 04 November 2010 - 05:02 AM

No, I do not punish the binocular. The manufacturer did that by not optimizing the design.
edz


EdZ,
The only thing Nikon should have made differently was giving their 18x70 a smaller field stop exactly the size which would have provided the same AFOV of 64 deg that the Fuji's 16x70 have (instead of 72 deg): Following your method, this would have substantially improved the numerical results just by switching off the outer, overlapping ring and forcing you to accept the same as the Fuji's 64deg to be 100%, thus changing all other relative numbers...
At the cost of TFOV? Yes, of course - as a natural result of its higher magnification!

Chris

#157 EdZ

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Posted 04 November 2010 - 05:17 AM

While the use of stellar limiting magnitude does go some way toward providing some measure of off-axis illumination, we are all aware of its weakness, namely the sensitivity to aberration-induced loss as the point source becomes spread out. A system which suffers worse blurring will perforce rate more poorly. This is much more an indicator of image definition than illumination.


I agree Glenn.

Actually, the loss of magnitude in the outer field could be more dependant on degree of aberration than anything else. I've discussed this in the past. A higher degree of aberration results in a higher proportion of magnitude loss due to aberration rather than fieldd illumination. I'm not intending this data point as an indication of illumination, since the loss due to one or the other cannot be separated.

What this does do is gives the user an indication of the "total" degree of losses. It's one thing to say stars are aberrated to an apparent size of 600 arcseconds at this point in the field. The user may be left asking, OK so what does that mean. It's another thing to say, that causes a loss of 1.5 magnitudes at that point in the fov. One might say, this is corroborating evidence.

Anyone who thinks they are getting more out of a wider but more greater aberrated field is sadly mistaken.

edz

#158 GlennLeDrew

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Posted 04 November 2010 - 12:11 PM

Ed,
Yes, I do agree that providing both aberration size and magnitude loss is much that either alone.

Anyone who thinks they are getting more out of a wider but more greater aberrated field is sadly mistaken.


I would provide a caveat with this statement. Astronomical observation is not confined to stellar objects alone. For extended objects, aberration is not as injurious to detection. I've always maintained that binos in particular should not necessarily be held to the same standards of off-axis definition as for a higher power telescope. When the outer parts of the field are relegated to peripheral vision (by always gazing more or less toward the field center and pan the instrument as necessary), the eye's much poorer non-foveal resolution still benefits enormously by having more field to take in, even when significantly aberrated.

#159 EdZ

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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.

edz

#160 gmbfilter

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Posted 04 November 2010 - 06:49 PM

This is a very long and winding thread,


Its the stuff of legend
I've learned more about binos than I thought possible
Thank you all

#161 Joad

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Posted 04 November 2010 - 08:29 PM

Thanks for the summary. I was having trouble figuring out what exactly was being debated here.

#162 KennyJ

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Posted 05 November 2010 - 02:16 AM

Perhaps this sums the thread up quite nicely .

http://www.youtube.c...h?v=Wst1G9GZAP4

Kenny

#163 mercedes_sl1970

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Posted 05 November 2010 - 05:06 AM

Perhaps this sums the thread up quite nicely .

http://www.youtube.c...h?v=Wst1G9GZAP4

Kenny


Kenny - for me it's been more of a case of Lucy...!

Andrew

#164 mercedes_sl1970

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Posted 05 November 2010 - 05:12 AM

P.S. And, no matter the findings, I still find the Nikons to be a fine binocular.

#165 Fomalhaut

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Posted 06 November 2010 - 06:25 AM

Very industrious, partially nice report.
However, as explained before, the try to measure field performance of instruments with different magnifications based on true fields of view does not really deliver comparable results.
This because higher magnifications normally produce smaller true fields and vice versa...
Chris

#166 Joad

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Posted 06 November 2010 - 11:54 AM

Since even I know that higher magnifications produce smaller fields of view, I think we can rest assured that EdZ knows this too. He has explained again and again and again here the technical rationale for his measurements and procedures and simply continuing to say "you're wrong" isn't getting us anywhere.

#167 hallelujah

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Posted 06 November 2010 - 01:16 PM

simply continuing to say "you're wrong" isn't getting us anywhere.


Speaking for myself, I have enjoyed following this post, page after page, as I have had alot of interest in the Nikon 18x70 for a number of years.

Unfortunately we have a person here who obviously lives by a different motto:
"Please don't confuse me with the facts, my mind is already made up".

#168 mark8888

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Posted 06 November 2010 - 01:58 PM

During my recent search for a pair of binoculars, I tested both the Fujinon 16x70 and the Nikon 18x70. I had no problems using the Fujinon, but as I reported at the time, I had a harder time with the Nikon than the Fujinon. I didn't know exactly what the problem was, but I felt disoriented, like I couldn't focus, or the afov was off somehow, or... something. Something felt very wrong to me. Having read the thread above, I can't help but wonder if I felt disoriented due to the "rolling ball" effect which is in evidence while panning, at least to some people. There are several other possibilities for the reason that I had problems, not least of which is the fact that the Nikons were used and maybe more damaged than I thought, or maybe I wasn't focusing on targets which were distant enough (though I doubt it), or maybe I couldn't focus because I only used them handheld (but I had no problems at all with the Fujinons, also handheld).

Anyway, I'm someone who gets motion sickness very easily, for example I can't ride a lot of common amusement park rides, I get sick on boats a lot faster than most people, etc. I was definitely panning the binos, by virtue of the fact that I was using them handheld. Anyway, FWIW, that was my experience.

As for me, this thread is perhaps best summed up by
http://www.youtube.c...h?v=4eD2sU8ocA8


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