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EdZ
Professor EdZ


Reged: 02/15/02
Posts: 18806
Loc: Cumberland, R I , USA42N71.4W
Nikon 8x40 Action EX vs 8x40 Action VII
      #1856112 - 09/21/07 11:01 AM

I've often heard the question, what's the difference between these two, so I bought one of each of the 8x42s to find out. (I've owned the AEx in three sizes for several years). Here's a few differences that can be noted between these two 8x42 models.

Action Extreme 8x40
is waterproof
has very nice twist out eye cups with several stops
significantly more stable eyepiece bar that has no rocking motion
eye relief is 17mm specified, 16mm usable
weighs 30oz
cost $125

Action VII 8x40
is water resistant
has fold out rubber eyecups
a less stable eyepiece bar that rocks with pressure
eye relief is 12mm specified, 11mm usable
weighs 26oz
cost $65

Also
both have 56-73mm IPD and near equal 8.1° fov
each has completely different hinge assembly and internal mechanics
both have what appears to be single coated prisms
both have significant bare metal in the objective cones and prism shelf


So, what are other differences between these two models?
Well for one the Action VII is listed as having an aspheric lens, the AE is not. This is an aspheric element in the eyepiece. But what does that do for you? Well it should help correct for some spherical aberration and make for a sharper view. Does it? Let's compare the view.

When viewing a close double for fine sharpness
The 8x42 Action VII can see a 36" double star out to about 25% from center.
The 8x42 Action EX can see a 36" double star out to about 35% from center.

When viewing further out in the field of view,
using the wide naked eye double theta1/theta2 Taurus, about 5.5 arcmin wide, this wide bright pair:
In the 8x40 Action VII at about 70% out in fov, blends into a long distorted line. This means total view is distorted by at least 5 arcmin.
In the 8x40 Action EX at about 70% out in fov, it distorts about 75% the space between the pair. This means view is distorted by 3.5-4 arcmin.

In both cases, there was substantial field curvature present. So it is apparent that the aspherical lens element in the Action VII does not act as a field flattener, and apparently neither model employs a field flattener.

With th1/th2 used as a target to focus out the curvature;
In the 8x40 Action VII at 50% out in fov, curvature could be focused out to a very good image, almost pinpoint.
In the 8x40 Action VII at 60% out in fov, curvature could be focused out to an acceptably decent image, but still slightly blurred.
The 8x42 Action EX at 75% out in fov, curvature could be focused out to a very good image, almost near pinpoint.

So what does this indicate?
Both the Action VII and the Action Extreme have considerable field curvature. The curvature was worse in the Action VII than in the Extreme. The curvature could be focused out of the Extreme further out in the fov than the Action VII. That means that other aberrations start to take over in the Action VII by 50-60% out. (By 70% out in the field, the Action VII lost a full magnitude due to a bloated star image.)

As a comparison, the Fujinon BFL 8x42 shows no field curvature. At 70% out in the field th1th2 Tau still looks decent without any refocusing required.

After field curvature, the first noticable aberration in the Action VII seems to be round out of focus disks, so probably spherical aberration. However, the predominant noticable aberration in the outer fov of the Action VII was astigmatism. It starts by 60% or sooner. By 70% out it is poor, by 80% out it is severe. The combination of curvature and astigmatism turns stars into lines 5 arcminutes long (300 arcseconds total aberration distortion) at 80% out.

The Extreme was not quite so bad. After field curvature was focused out, at 60% out there was little residual aberration. At 70% out there was minor aberration.

For comparison:
Nikon Action VII 8x40 has 240 arcsec total aberration at 55-60% out. 8°fov
Nikon Action VII 8x40 has 300 arcsec total aberration at 70% out. 8°fov
Nikon Action EX 8x40 has only 200 arcsec total aberration at 65-70% out. 8°fov
Fujinon BFL 8x42 has only 40 arcsec total aberration at 55-60% out. 6.5°fov
Nikon Action EX 10x50 has only 40 arcsec total aberration at 60% out. 6.1°fov
William Optic 7x50 has only 60 arcsec total aberration at 80% out. 7.4°fov
Oberwerk Mariner 10x60 has 40 arcseconds total aberration at 80% out. 5.1°fov
Nikon SE12x50 has only 40 arcsec total aberration at 90% out. 5.0°fov

The aspheric lens in the Action VII does not reduce the aberrations to less than the Extreme model. The Extreme model shows a somewhat better image at 60% to 80% out. Like almost all binoculars, the Extreme suffers from astigmatism, but it's not as bad as the Action VII. Coma was noticable in the Extreme between 80-100% out.

In summary, I would say the outer 30% of the fov in the Action VII is rather poor. So what you really end up with is an 8x40 Action that has a decent view over 5.5°. The Extreme goes a little wider, maybe out to 6.0°. The Extreme has better correction for all aberrations all across the fov. Curvature in the EX is less to start with, and when curvature is focused out, there is less residual aberration in the EX. Even without the use of an aspheric lens, it has lower overall aberrations. Coma and especially Astigmatism are supressed in the EX to a greater degree further out in the field than in the Action VII. Therefore the Action Extreme has a wider usable fov.

Other differences not addressed here.

edz


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EdZ
Professor EdZ


Reged: 02/15/02
Posts: 18806
Loc: Cumberland, R I , USA42N71.4W
Re: Nikon 8x40 Action EX vs 8x40 Action VII new [Re: EdZ]
      #1867743 - 09/26/07 04:43 PM

More comparison between Nikon 8x40 Action EX vs 8x40 Action VII

after two complete rounds of resolution tests (did it once, did it again)

At normal power the Nikon EX 8x40 achieves 12% (1 step on the chart) better resolution on axis than the Nikon VII 8x40.

At 6x boosted power the Nikon EX 8x40 achieves 24% (2 stepson the chart) better resolution on axis than the Nikon VII 8x40. 9.7 arcsec vs 10.8 arcsec for the Action VII.


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Kimmo Absetz
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Reged: 10/12/05
Posts: 119
Re: Nikon 8x42 Action EX vs 8x42 Action VII new [Re: EdZ]
      #1868785 - 09/27/07 02:07 AM

Ed,

Like you in this test, I have thus far never seen a binocular with "aspheric" lenses advertised in the eyepiece construction that would actually show any tangible benefits. Rather, they have always had very poor edge performance. Of course, this is probably not due to the aspherical lens design as such, but rather the price/quality level of these binoculars in general, and I am open-minded about the possibility of a binocular someday appearing that does use aspherics in the eyepiece with good results. As it stands, though, I consider it a marketing slogan that is likely to indicate that the eyepiece is a simple, poor quality design.

Kimmo


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