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CN Report: Small Binocular Reports A Dozen 8's


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Small Binocular Reports A Dozen 8s
3-8-08
Ed Zarenski

This is one in a series of "Small Binocular" reports that will detail and summarize all my findings from eight months of tests and measures on over 30 binoculars. Sizes ranged from 7x50, 8x32 and 8x40 up to 8x42 and 10x42 roofs, 10x50, 10x60 and 12x50s. These are all sizes that could be hand-held and used for either terrestrial use or astronomy. Sprinkled throughout the list of binoculars are several benchmark models that give a good indication what all the others should hope to achieve. Here are the test results for a dozen 8 power binoculars, including 8x40s, 8x42s, several roof prism 8x42s, and a few larger or smaller than that nominal size range. Be sure to refer to the other reports, especially the Small Binocular Score, the report showing the summary scores for 16 different measured aspects for all 34 binoculars tested.





Clockwise from front left: Garrett Apo 8x42 roof, Celestron Regal 8x42 roof, Fujinon BFL 8x42, Nikon Action Extreme 8x40, Nikon Action 8x40, Pentax PCF WP II 8x40, Bushnell Legend 8x42 roof, Oberwerk Mariner 8x40, Nikon SE 8x32. Center: Garrett Classic 8x45.


For the most part this portion of the study is based on 8x40 and 8x42 binoculars. However, a few other 8s that fit best here were included, such as 8x56 and an 8x45. Again you will see even though those are nominally larger, they fit fairly close in with this size range. Also, the 8xroofs were included here even though they were reviewed with the roofs. The fact that they are roofs does not preclude them from being included in this appropriate 8x size comparison. The Nikon SE 8x32 is used as a benchmark here. In some cases you will see this little 32mm binocular performs as well or better than some of the nominal 40/42mm binoculars tested.


Binocular Basics

actu

Net

actu

use

range

oz.

gm

spec

prism

$$$

Small Binoculars

Mag

Aper

FOV

ER

IPD

wgt

wft

coat

coat

cost

Oberwerk 8x56

8.1

48

5.7

21

59-72

36

1022

fmc

fmc

99

Garrett Classic 8x45

8.1

38

7.3

18

59-74

29

823

fmc

fmc

100

Celestron Regal 8x42 rp

8.1

42

6.3

17

58-74

25

709

fmc

fmc/p

169

Bushnell Legend 8x42 rp

8.2

41

6.5

17

58-74

25

709

fmc

fmc/p

249

Garrett DCF 8x42 Apo rp

8

41

6.7

19

57-71

23

653

fmc

fmc/p

200

Swift Ultralite 8x42

8

41

6.5

19

51-76

21

596

fmc

fmc

169

Fujinon BFL 8x42

8.0

40

6.5

11

57-73

24

681

fmc

fmc

189

Pentax PCF WP II 8x40

8.0

39

6.3

13

57-74

31

880

fmc

fmc

149

Nikon Action Ex 8x40

7.9

39

8.1

14

56-73

30

851

mc

MgF

124

Nikon Action VII 8x40

7.9

38

8.15

11

56-73

26

738

mc

MgF

65

Oberwerk Mariner 8x40

8.0

32

8.0

16

62-73

33

936

fmc

fmc

139

Nikon SE 8x32

8

32

7.6

14

53-73

22

624

fmc

fmc

550


Values are measured actual magnification x effective aperture, True field of view, usable eye relief, interpupilary range, weight, lens coat/prism coat and retail purchase price. The Nikon SE 8x32 is included as a benchmark.


More Basics

The Oberwerk 8x56 is heaviest at 36oz. (1020g.), and the small Oberwerk Mariner 8x40 is not far behind at 33oz. (930g.), both these about the weight of a normal 10x50 and even heavier than a few 10x50s which go as low as 30oz. (850g.). Towards the heavy end, about the same weight as the lightest 10x50s, are the Pentax PCF WP II and the Nikon Action Ex. Quite a few of these weigh in close to 25oz. (700g.). At the very lighest end of the spectrum are the Fujinon BFL, the Garrett Apo roof and the Swift Ultralite.











The Fujinon BFL weighs only 24 oz. (680gm.) and is like a little baby binocular in comparison to the monster sized FMT-SX 10x70. Even the 49oz. (1400gm) Fujinon FMT-SX 10x50, which is much smaller than the FMT-SX 10x70, still has considerably more heft than this little 8x42. The 8x42 BFL, not necessarily the lightest or smallest, is one of the most comfortable small binoculars to carry around.









 



The Fujinon BFL is just a bit smaller than the Nikon SE 10x42, shown in middle. The Nikon SE 8x32, left, is a bit too small for my hands.









I like the one-piece style cover that fits snuggly over both eyepieces. Nikons, the Regal LX as well as Bushnell, Swift and the Oberwerk Mariner all have the same style one-piece eyelens cover.

I don't like objective push-in caps. The Regal, the Nikons, the Mariner and the Classic all have push in objective caps. The Pentax the Swift and the Fujinon all have push over caps, but none are captive and all are loose. The Oberwerk 8x56 has good fitting push over caps. The Bushnell roof has captive objective caps push over.

You don't get a lot of room for an L bracket between the barrels of a roof prism binocular. The narrow bracket that came with my Oberwerk Ultra 15x70 is only 10mm wide and works perfectly. None of the roofs can be used on the Far Sight Binocular Mounting bracket. No other standard L bracket I own would work for the roofs, although there are other narrow L brackets available that would work. However, I must say, difficulty mounting small roof prism binoculars should not be considered a problem. Very few people will be mounting small 8x42 roofs. I do have a velcro strap style adapter from Eagle Optics that works well with all the roofs and the lighter porros. All of the 8x porros are easy to mount on any type bracket.

The Pentax porro eyeguard twists and stops at both an intermediate position and full out. It has no unwanted loose movement. The GO 8x45, the Fujinon BFL, the Nikon Action, the Swift Ultralite and the Oberwerk 8x56 all have folding rubber eyecups. The Oberwerk Mariner has a hard rubber eyeguard that twists out with friction that holds it in place at any position. The Regal has a push/pull eyeguard with one positive click midway. It did not move from the midway or full out click positions. The Bushnell Legend porro twists out to three very positive detente settings. The Nikon Action Extreme also has a hard rubber eyeguard that twist out. Similar to the Legend, it has three positive positions with no slip. The Garrett Apo roof has a twist out eyeguard, but it seems it will not stay put at any intermediate position, so it must be used either all the way in or all the way out.

The Regal is waterproof/fogproof, O-ring sealed and nitrogen purged. But, if I'm not mistaken, so are the Bushnell Legend and the Garrett Apo roofs. Of the porros, the Oberwerk 8x56, the Swift Ultralite and the Nikon Action are NOT waterproof.

The Swift Ultralite, Pentax and Nikon AE have very little pincushion. The Oberwerk Mariner 8x40 and the Garrett Classic 8x45 have the most pincushion. The Garrett roof has the least pincushion of the roofs. None of the others have severe pincushion. Keep in mind pincushion has absolutely no affect on astronomical observing. However, it does have considerable affect for terrestrial users, and all of these are considered good size cross-over binoculars. A small amount of pincushion is desirable as it helps eliminate the rolling ball effect for terrestrial use. So pincushion is a meaningful criteria that affects terrestrial users differently than astro users.


Eye Relief – Diopter - IPD
With the exception of the Fujinon BFL (speced er=15mm) and the Nikon Action (speced er=12mm) the specified eye relief on all of these is quite substantial, between 17-24mm. The Bushnell roof (17mm), the Garrett roof, the Swift Ultralite, the Oberwerk Mariner and the Garrett Classic come very close to specified and all have long usable eye relief. The Pentax PCF WP II is specified at 20mm, it actually has only usable eyerelief of 13mm.

Several of these binocular have eye lenses and the metal rim surrounding the eye lens positioned too close to the top of the retracted eye guard. Garrett Classic, Garrett roof Swift Ultralite And Nikon Action all have only only 2mm clearance to the eye lenses when the eyecups are turned fully down. This is insufficient distance to prevent contact with eye glasses, requiring that the eyecup be twisted out somewhat so eyeglasses don't hit the binocular eye lens. The Swift metal rim is covered with the rubber eyecups, so the metal on that one is not a proble. On the others both the metal rim at the edges of the eye lens and on all of them the fact that the eye lens is only 2mm deep means you need to be careful when using these with eyeglasses.

Eye Relief

spec

dist

rcss

usable

usable

Small Binoculars

ER

exit

lens

ER

w/cup

Oberwerk 8x56

24

24

3

21

9

Garrett Classic 8x45

19

20

2

18

4

Celestron Regal 8x42 rp

20

21

4

17

7

Bushnell Legend 8x42 rp

18

21

4

17

9

Garrett DCF 8x42 Apo rp

20

21

2

19

9

Swift Ultralite 8x42

20

21

2

19

7

Fujinon BFL 8x42

15

17

6

11

5

Pentax PCF WP II 8x40

20

18

5

13

3

Nikon Action Extreme 8x40

17

18

4

14

4

Nikon Action VII 8x40

12

13

2

11

4

Oberwerk Mariner 8x40

18

19

3

16

9

Nikon SE 8x32

17

19

5

14

5



With the curvature of my eyeglass lenses, at least 3mm depth is needed below the eyeguard to keep eyeglass lenses from hitting and scratching the binocular eye lens, or just as bad, scratching my eyeglass lenses. It would cost me more to replace my eyeglass lenses than it would to replace these binoculars. The Celestron Regal LX has 4mm depth. The Bushnell Legend has 4mm. All of these others have the rubber eyeguard raised just enough above the metal eyepiece edge rim to prevent the metal from touching my eyeglasses.

The Fujinon BFL right diopter is the rotating eyepiece style, as is the Nikon Action, the Swift and the Garrett Classic. The BFL has clickstops. The Nikon AE, Pentax, and Oberwerk Mariner have a slide bar under the right eyecup.

The Garrett roof has a right diopter ring that seems designed to prevent it from accidentally being moved. It is narrow, low profile, under the right eyecup, difficult to grip and tight, that it’s difficult to turn them while looking through the binocular. The Bushnell right diopter ring is prominently raised and is very easy to use. The Celestron Regal is unique in that the right eyecup is push/pull for eye relief and is twist for diopter. The first 8xRegal I received broke within 2 days. The replacement works, but is the coarsest movement of any right diopter on any of these binoculars.

Most of these are very similar in IPD range, ranging from 56-73mm to 58-74mm. The Swift Ultralite accommodates from 51mm-76mm, the widest range of all. However, a few have a wide minimum IPD. While 58mm is close enough for most people, some adults will need 57mm and many children with close-set eyes need even less to see with both eyes. The Oberwerk 8x56 and the Garrett Classic 8x45 have a minimum IPD of 59mm, and the Oberwerk Mariner minimum is 62mm, these sizes not suitable for many children.


Close Focus
Most of the porros have a close focus from 13ft.to 15ft. The roofs all focus to within 5-7ft. The Pentax and the Nikon Action get as close as 11ft. the Oberwerk 8x50 can get no closer than 50ft. Using 20ft as the focus point, those that can focus to 20ft have between 80-87% of the fov overlapped for binocular vision. The roofs, which all focus to much closer than 20ft, have closer to 90% of the fov in binocular vision at 20ft.

What you really get with these binoculars when it comes to close focus (assuming at 10ft) is a "binocular vision" field of view about 10 inches wide. Both the Bushnell Legend (6.5° fov) and the 10xRegal (6.0°fov) show nearly identical results. At a distance of 10 feet they can see 31-32cm with only 25 cm of that field overlapped, so for binocular vision they see 10 inches out of just over 12 inches. In these same binoculars, when viewing at 100 feet (30m) the barrel overlap is off by less than 5% of the fov and you get a 10 foot wide view with binocular vision while only 6-8 inches is not overlapped.

Internal Focus
These three roofs are internal focus. I can observe the internal sliding mechanism sleeve in front of the prism. If a binocular is internal focus, and therefore, the eyepieces do not move, then an internal lens is moving to achieve focus and therefore focal length and resultant light cone gets modified slightly so the focal point will hit the unmoving eyepiece to change from close focus to infinity. That probably means all these roofs are changing magnification as you move towards closer focus. I did a quick check of the 8xRegal at a focus distance of about 10ft and found magnification close to 8.5x. That's a 4-5% increase in magnification. The Bushnell shows about 8.6x, an increase of 5%.



Close Focus

****

close

dial

dial

Small Binoculars

focus

focus

3-30

30-100

Oberwerk 8x56

CF

50

na

135

Garrett Classic 8x45

CF

15

270

120

Celestron Regal 8x42 rp

Cf in

6

300

30

Bushnell Legend 8x42 rp

Cf in

7

180

30

Garrett DCF 8x42 Apo rp

Cf in

5

270

60

Swift Ultralite 8x42

CF

14

270

45

Fujinon BFL 8x42

CF

14

145

45

Pentax PCF WP II 8x40

CF

11

300

60

Nikon Action Extreme 8x40

CF

13

330

30

Nikon Action VII 8x40

CF

11

285

45

Oberwerk Mariner 8x40

CF

15

108

54

Nikon SE 8x32

CF

9

300

90



Slow or Fast Focus
As I've done with all the binoculars in the Small Binocular studies, I've attempted to class them as slow or fast focus. But what I found was, fast or slow is not necessarily consistent across all distance ranges. So, I measured the dial degrees turn needed to go from 3 meters to 30 meters (10feet to 100feet) and then measured the degrees turn to go from 30m to 100m (100ft to 300ft). For instance both the Bushnell roof and the Regal roof take only 30° of focus dial turn to focus from 30M to 100M. Typical fast focus binoculars have a total dial turn 20-deg to 60-deg for the 30M-100M range. However, for the range from 3M to 30M, the Bushnell can cove that distance with only 180-deg of focus dial turn, while the Regal needs 300-deg of turn. The Regal would not be considered fast focus in the short range.


Most of these binoculars, in the close range from 30m to 3m (100ft to 10ft), take about 300-deg of dial turn to focus. Based on the 34 binoculars in my test group, this is very SLOW focus for this close 3m-30m range. The fast focus binoculars in my test group cover this same distance range with anywhere from 100-deg to 180-deg of dial turn. Only ONE binocular I've measured was slower focus than 300-deg in this range. Only the Bushnell Legend and the Fujinon BFL are fast focus in the range from 3m to 30m (10ft to 100ft), with little difference between them all.

All BUT two of these binoculars are fast focus in the range from 30m to 100m (100ft to 300ft). The Oberwerk 8x56 and the Garrett Classic 8x45 are slow focus in this range.

FOV and Field Sharpness
Of the roofs, the Celestron Regal is 6.3-deg, the Bushnell Legend is 6.5-deg and the Garrett Apo is 6.7-deg. Several of the porros have a wide fov that exceeds 8-deg. Most of the other have a fov exceeding 6.5-deg. The fov of the Oberwerk 8x56 is only 5.7-deg, the smallest of all these.

The 8xRegal has by far the best sharp fov, what could be considered sharp to the edge fov, with only 1 arcmin total distortion all the way out at 95% of the field. There are only four other binoculars in these tests that could equal or exceed that mark. All four are benchmark binoculars, two Fujinons and two Nikon SEs.

Two porros with the best sharp fov are the Fujinon BFL and the Pentax PCF WP II. Both have 85% sharp and 90-95% usable.

Field of View degrees

spec

actu

calc

sharp

sharp

sharp

limit

Small Binoculars

FOV

FOV

Afov

600arc"

1200arc"

fov

fov

Oberwerk 8x56

6.0

5.7

46

75

75

4.3

4.3

Garrett Classic 8x45

8.3

7.3

59

70

70

5.1

5.1

Celestron Regal 8x42 rp

6.5

6.3

51

95

95

6.0

6.0

Bushnell Legend 8x42 rp

6.3

6.5

54

75

75

4.9

4.9

Garrett DCF 8x42 Apo rp

7.0

6.7

54

70

70

4.7

4.7

Swift Ultralite 8x42

6.6

6.5

52

75

80

4.9

5.2

Fujinon BFL 8x42

6.5

6.5

52

85

90

5.5

5.9

Pentax PCF WP II 8x40

6.3

6.3

50

85

95

5.4

6.0

Nikon Action Extreme 8x40

8.3

8.1

64

60

65

4.9

5.3

Nikon Action VII 8x40

8.2

8.15

64

60

65

4.9

5.3

Oberwerk Mariner 8x40

8.4

8.0

64

70

70

5.6

5.6

Nikon SE 8x32

7.5

7.6

61

95

95

7.2

7.2


It would seem that one design feature that contributes to a high level of outer field sharpness is the use of very narrow Afov eyepieces. For instance the 8xRegal have 51-deg Afov eyepieces, low for any of these 8x binoculars. It has the sharpest outer field image. Fujinon BFL (52-deg Afov) and the Pentax (50-deg Afov) are similar in that Afov is very narrow and outer field aberration is well controlled. These three binoculars, even though they do not have the widest Total fov, do indeed have the widest usable fov of all in this list.

The Nikon AE and the Nikon Action deteriorate rapidly and have only 65% of the fov usable, but since they start out very wide, that does result in more than 5-deg usable fov. The Oberwerk Mariner, the Garrett Roof and the Garrett Classic only get 70% usable fov with 2 arcmin distortion. Both the Bushnell roof and the Oberwerk 8x56 quickly fell off by 75% out.

Two arcminutes of total distortion in your image provides no more useful information. Stars are either distorted blobs or long streaks. The image has lost perhaps two full magnitudes of faint stars.

The Oberwerk 8x56 uses the narrowest Afov eyepieces of any in this list, but do not fully capitalize on that feature. They end up with the narrowest Tfov of all these, and the narrowest sharp fov and usable fov.


Curvature and Depth of Field
The Nikon Action Extreme, Nikon Action and Oberwerk Mariner have the most field curvature. The Bushnell Legend has the most field curvature of the three 8x42 roofs, but less than any of the porros first mentioned. The Bushnell has 1 arcmin of curvature at 60% out in the field, and 90 arcsec at 90% out. The three porros here all have nearly 2 arcmin of curvature at 60% out, and 2.5 arcmin at 90% out. The Fujinon BFL and the Celestron Regal roof have very little curvature, the 8xRegal has almost none.

Binoculars with more field curvature have greater apparent depth of field in front of the focus point. It would seem therefore that a field flattener lens, which would be desirable for an astro viewer to get as flat a field as possible, might work against a terrestrial viewer looking for the greatest depth of field.

An astronomer would prefer all binoculars to have as little field curvature as possible so the entire plane of the fov has as little distortion as possible. It is not unusual to find that a binocular with much less sharpness out at 60% or 70% in the fov has a much greater amount of field curvature than a binocular which appears sharp out to 80-90% of the fov. A terrestrial viewer might want to consider how field curvature affects the view, and may in fact find field curvature to be a useful aberration. While it does nothing to add to depth of field further distant than the plane of focus, field curvature provides for closer objects to appear in focus as they range out across the fov.

Depth of Field example:
The Fujinon BFL 8x42 has low field curvature (approx 15 arcsec curvature at 60% out, 25 arcsec at 70% out and still only 60 arcsec of curvature at 90% out). Basically, that's pretty close to a flat field. When focused at 50m, objects at 40m appear sharper at 30% out in the field and objects at 30m appear shaper at 50% out, but objects at 25m are not in focus and cannot be seen better anywhere in the field. I would say the BFL has a narrow depth of field.

The Celestron Regal 8x42 has even less field curvature than the Fujinon BFL. When focused just as the BFL in the test above, the Regal sees 30m appear shaper at 80% out. No objects closer than that can be seen clearly at any point in the fov.

The Bushnell Legend 8x42 has the most field curvature of the roofs included here (45 arcsec at 60% out, 75 arcsec at 70% out, 100 arcsec at 90% out). When focused at 50m, objects at 40m appear sharper at 30% out in the field and objects at 30m appear shaper at 40% out. Objects at 25m are seen clearly at 70% out in the field and objects even slightly closer are seen clearly further out in the field.

The Nikon Action Extreme has field curvature of (50 arcsec at 60% out, 120 arcsec at 70% out, 150 arcsec at 90% out). When focused at 50m, objects at 40m appear sharper at 30% out in the field and objects at 30m appear shaper at 50% out. Objects at 15m are seen clearly at 70% out in the field and objects even slightly closer at 12m are seen clearly focused further out at 90% in the field.

The Nikon Action Extreme, decried in some circles for it's outer field aberrations, has one of the strongest measures of field curvature of all the 8s measured. The effect is has on depth of field is dramatic. When the binocular is focused on an object 200 yds distant, the fissures and nodules in tree bark on trees at 60 yds can be studied in detail if positioned at 50-60% out in the field of view. Water droplets hanging from a tree limb at 30yds are seen very clearly in focus at 80-90% out in the fov. When the same experiment is conducted with the Fujinon BFL, no detail can be seen in the tree bark at 60 yds from any position in the field of view and the branches with water droplets at 30yds are a blurry mess.

From these tests it seems apparent perhaps the strongest influence on depth of field in all binoculars is the amount of field curvature in the lens. Field Curvature, an aberration frowned on by astronomers, can be one of the greatest assets to a terrestrial viewer.


Aperture
With a few noted exceptions most of these binoculars come very close to the specified aperture. The 40mm Nikon Action prism shelf stops the aperture down to 38mm. The Fujinon BFL 42mm is stopped to 40mm. None of these have any significant losses of the light due to exposed prism edges or prisms interfering in the light path.

You can see from the results in the data table, the three different tests for aperture don't all give the same results. Measuring exit pupil is difficult. In addition, even though my dial caliper can give readings to increments of 2/100ths mm, I round my readings up or down to the nearest 1/10th mm, so that could easily account for a small difference in the three types of readings. Measuring the aperture with a loupe is direct, but there is some difficulty in obtaining readings that are any more accurate than to a mm, especially if the stop is a baffle in front of the prism, in which case great care must be taken to insure the proper reading is obtained. So more potential slight variance now exists. The laser is probably the most accurate indicator, but once again, sliding the laser across a glass plate to each position at the edge of the aperture and recording fine measurements of that diameter is probably no more accurate than a mm. So it's easy to have differences in the readings from these methods. However, none of the individual methods should be off by more than a mm, and certainly none of the methods nor is the end result off by several mm.


Effective Aperture

spec

spec

spec

actu

actu

Aper

Aper

Aper

Aper

chord

Net

Net

Small Binoculars

Mag

Aper

pupil

Mag

pupil

pupil

loupe

laser

avg3

%loss

Aper

Aper

Oberwerk 8x56

8

56

7.0

8.1

6.0

49

47

47

48

0%

48

-15%

Garrett Classic 8x45

8

45

5.6

8.1

4.8

39

38

39

39

2%

38

-16%

Celestron Regal 8x42 rp

8

42

5.3

8.1

5.1

42

42

42

42

0%

42

-1%

Bushnell Legend 8x42 rp

8

42

5.3

8.2

5.1

42

41

41

41

2%

41

-3%

Garrett DCF 8x42 Apo rp

8

42

5.3

8

5.2

42

41

42

42

1%

41

-2%

Swift Ultralite 8x42

8

42

5.3

8

5.1

41

41

41

41

0%

41

-3%

Fujinon BFL 8x42

8

42

5.3

8.0

5.0

40

40

41

40

2%

40

-6%

Pentax PCF WP II 8x40

8

40

5.0

8.0

5.0

40

39

38

39

1%

39

-3%

Nikon Action Ex 8x40

8

40

5.0

7.9

4.8

38

39

40

39

0%

39

-3%

Nikon Action VII 8x40

8

40

5.0

7.9

4.8

38

38

38

38

0%

38

-5%

Oberwerk Mariner 8x40

8

40

5.0

8.0

4.0

32

32

31

32

0%

32

-21%

Nikon SE 8x32

8

32

4.0

8

4.0

32

32

33

32

0%

32

1%



The noted exceptions with significantly reduced aperture are the Oberwerk 8x56, the Garrett Classic 8x45 and the Oberwerk Mariner 8x40. All of these are stopped down to an effective aperture 15% to 20% less than specified. Following are two photos that show exit pupils compared to a standard. The visual evidence is unmistakable.


Here you see the Fujinon FMT-SX 10x50 on the bottom of both photos. On the left is the Oberwerk Mariner 8x40. On the right are the Garrett Genesis 10x50 and the Garrett Classic 8x40. The Fujinon has a measured exit pupil of 4.9mm. By specifications, all the other binoculars in these photos should have equally large or larger exit pupils compared to the Fujinon. It is pretty easy to see the photos show that is not the case.


Baffles and Blackening
The Pentax PCF WP II 8x40 is well baffled and blackened. Any internal metal is very dark. There is no bright gray metal between the objectives and the prisms. The baffles are very closely sized to come as close to the prism aperture as can be without interfering in the light path.

The Fujinon BFL is exceptionally well baffled and blackened. All internal metal is very dark. There is no bright gray metal between the objectives and the prisms. The baffles are perfectly sized to the light cone between the objective and the prism aperture. The inner section of the objective cone wall is fine ribbed to prevent reflections on the inside of the wall.

The Regal interior baffles and blackening are pretty good. There are two metal baffle rings and the inside wall is cut with ridges and blackened. There is some grey metal near the prism housing, but it is pretty dull grey. The baffles are near perfectly sized when the binocular is focused at infinity. Because it is internal focus and that assembly is in front of the prism, and because the baffle size remains constant, it is therefore a bit undersized when it is moved forward to set the binocular for close focus.



The Nikon Action baffle is grossly undersized (the baffle hole is too big). The light cone from the objective never comes near the baffle before it hits the edge of the prism aperture. The inside of the objective barrel is blackened, however all the metal around the prism is bright gray.

Here on the right you see, the outer bright ring is the edge of the aperture, the second bright ring is the baffle edge and the inner gray ring is the prism aperture. On the left I have lined up the aperture with the baffle. Notice how much of the prism shelf is exposed. The objective aperture, the baffle edge and the prism aperture should all line up.

The Nikon Action Ex baffle is also considerably undersized. The light cone edge from the objective too the prism aperture should pass very close to the edge of the baffle. The baffle edge is well outside the diameter of the light cone. The inside of the objective barrel is well blackened, however all the metal around the prism is bright gray.

The Garret roof and the Bushnell Legend roof have bright grey metal in near the prisms. Just like the internal focus Regal, the Bushnell and the Garrett baffle must be sized for when the binocular is focused at infinity, which they are. The baffles become less and less sized properly as the binoculars are adjusted towards close focus.

The Oberwerk Mariner 8x40 baffle is grossly oversized. The baffle ring hole is too small for the light cone. It can easily be seen as the culprit for reducing the effective aperture of the Mariner from 8x40 all the way down to 8x32.



An attempt is made with this photo of the Mariner to show the edge of the objective lined up with the edge of the baffle. You should be able to see the same side (the outer edge) of the prism aperture in the background. It is dramatically cut off. In addition, take note of the shiny surface (green reflection) at the entrance to the prism aperture. There should not be any shiny surfaces anywhere in the objective cone or near the prism aperture.

Coatings
All these binoculars appear to have multi-coated objectives and eye lenses. Coatings should not reflect light. Coatings that reflect more light have less light passing thru the lens.

The Celestron Regal by far appears to have coatings that reflect the least amount of light. No other binocular here is similar to the Celestron Regal. The Regal is similar to the Nikon SE and the Fujinon FMT-SX

The Pentax PCF WP II is similar to the Regal in that it reflects very little, ranked second best among this group. The Bushnell Legend roof, the Oberwerk Mariner, Swift Ultralite and Fujinon BFL are all very similar. They all have more reflection than the Pentax, but less than the Nikon AE and Nikon Action.



Left: Celestron Regal 8x42 top, Bushnell Legend 8x42 roof, Pentax PCF WP II 8x40 bottom
Right: Nikon Action EX 8x40 top, Oberwerk Mariner 8x40, Fujinon BFL 8x40 bottom

The Garrett Classic has nice coatings. Coatings are on a par with the Oberwerk Mariner. Coatings are more reflective than the Pentax but less reflective than the Nikon AE.
The Nikon Action Extreme and the Nikon Action coatings both reflect more than the Pentax PCF WP II, Bushnell Legend, the Mariner or the Fujinon BFL.

The Nikon AE lenses are multi-coated, however the prisms appear to be only single coated, preventing that one from being labeled FMC. Yet the Nikon AE see stars equally as faint as the Pentax and both of them see slightly fainter stars than the Garrett Classic.

The Garrett Apo roof reflects a lot of light off the objective lens. The difference here from best to worst is that it was very difficult for me to see my reflection in the Regal and no detail at all could be seen. In the Garrett, I could easily see facial features in detail and could see the color of my shirt. In tests, the Garrett roof records the lowest LM, possibly in agreement with a higher reflectivity in the coatings. All these roofs are listed as FMC and phase coated.

The Bushnell has "rainguard" coatings. If you've ever used rainguard applied to your windshield, you know it virtually eliminates the need to use wipers in the rain. This coating is intended to do the same on the Bushnell.



Limiting Magnitude
With a variety of observations from different nights, I compiled a list of the best Limiting Magnitude for each. The best out of this group are the Oberwerk 8x56, the Regal, the Bushnell, the Pentax and the Nikon AE, all of these reached a limit of mag 9.6. I never saw stars deeper than mag 9.1 with the Garrett Apo, the Nikon Action or the Oberwerk Mariner. With the exception of those binoculars that never saw any deeper than mag 9.1, all the other binoculars saw between mag 9.4 and mag 9.6. Typically these better 8x binoculars see about ½ magnitude less than a good 10x50.


Prism Vignette and Illumination
Light transmission is dependant on more than just good coatings. Excellent coatings and poor internal beam transfer can result in poor output. On the other hand, excellent beam transfer and illumination, even with less than premium coatings may result in a binocular that appears brighter and sees fainter objects.

The Garrett roof, the Regal roof and the Bushnell roof all gave very good readings for control of internal vignette and lack of tilt in the light path. None of the above had any significant tilt and all showed very good transfer of the test beam into the exit pupil. The Oberwerk 8x56 the Garrett Classic 8x45, the Swift and the Pentax showed poor readings, all showing some tilt in the light path and considerable vignette of the beam before it reached the exit pupil. In both instances, even with the test beam in the very center of the objective lens, large portions of a 5-deg beam were cut off and never reached the exit pupil. No position could be found on the objective lens where the entire beam would pass to the exit pupil.

Normal function shows the entire 5-deg wide circle and crosshairs laser target pattern will pass thru when the test beam is placed perpendicular to the optical axis and anywhere within the central 20-30% of the objective lens. The Fujinon BFL 8x42 set the highest standard for superior function by transmitting the entire beam pattern from every point in the central 50% diameter of the objective lens. The Pentax roof and the Oberwerk roof had the lowest scores for internal prism vignette of all binoculars tested in this study.




Light Transfer

tilt

tilt

100%

75%

Exit

MAX

LM best

Small Binoculars

left

right

beam

beam

Pupil

Lux

5.2-5.4

Oberwerk 8x56

15

15

0

50

6.0

870

9.6

Garrett Classic 8x45

10

15

0

60

4.8

770

9.4

Celestron Regal 8x42 rp

10

10

10

50

5.1

579

9.6

Bushnell Legend 8x42 rp

4

3

15

55

5.1

560

9.6

Garrett DCF 8x42 Apo rp

10

2

35

55

5.2

660

9.1

Swift Ultralite 8x42

15

10

0

55

5.1

630

9.5

Fujinon BFL 8x42

7

3

50

70

5.0

751

9.4

Pentax PCF WP II 8x40

25

20

0

40

5.0

770

9.6

Nikon Action Extreme 8x40

5

5

30

60

4.8

880

9.6

Nikon Action VII 8x40

10

0

25

50

4.8

810

9.1

Oberwerk Mariner 8x40

0

0

30

45

4.0

630

9.1

Nikon SE 8x32

2

2

25

60

4.0

603

9.1



The Oberwerk 8x56, the Nikon AE and the Nikon Action appear to have high marks for illumination of the exit pupil. However, generally, as seen from the data in the entire list of 34 binoculars, max lux appears to trend higher for a larger exit pupil. Therefore the larger exit pupils should have higher readings. The Oberwerk 8x56 scored well, as did the Nikon AE and Nikon Action. The roofs all scored typically low in this test.


Resolution
Normal resolution covered a fairly narrow range, with almost all thse binoculars doing fairly well. The Nikon AE and the Fujinon BFL both recored the best values at 81 arcsecconds apparent and the Pentax a very close 82 arcseconds. The Garrett Classix the worst at 92 arcseconds and the Oberwerk 8x56 could reach only 88 arcsec, but that fairly respectable.

Boosting the resolution test power by 6x normal, the Pentax was able to see the finest resolution at 187 arcseconds. 3.8 arcseconds for an 8 power binocular is really exceptional. The Celstron Regal was able to see 4.1 arcseconds for an apparent resolution of 204 arcsec. The Celestron Regals have some of the best boosted resolution in the entire study, but here in the 8x group the Pentax is the standout with some of the best all around resolution readings across the board.

The Bushnell Legend, the Fujinon BFL and the Oberwerk Mariner put up the best figures for handheld resolution. In fact, the Bushnell Legend is the only roof among the top group for handheld resolution, all the rest are small porros.




Resolution USAF chart

actu

USAF

apprnt

boost

USAF

apprnt

USAF

apprnt

Small Binoculars

Mag

res

res

Mag

x6.15

res

res handheld

Oberwerk 8x56

8.1

10.8

88

50

6.8

339

15.3

124

Garrett Classic 8x45

8.1

11.5

92

50

6.8

338

15.3

123

Celestron Regal 8x42 rp

8.1

10.3

83

50

4.1

204

16.0

130

Bushnell Legend 8x42 rp

8.2

10.3

84

51

5.4

274

14.5

119

Garrett DCF 8x42 Apo rp

8

10.8

87

49

5.4

266

15.3

122

Swift Ultralite 8x42

8

10.8

86

49

4.8

236

16.2

130

Fujinon BFL 8x42

8.0

10.3

81

49

4.6

223

14.5

115

Pentax PCF WP II 8x40

8.0

10.3

82

49

3.8

187

15.3

122

Nikon Action Extreme 8x40

7.9

10.3

81

49

5.4

262

15.3

121

Nikon Action VII 8x40

7.9

10.8

85

48

6.8

329

15.3

120

Oberwerk Mariner 8x40

8.0

10.8

87

49

5.1

251

14.5

116

Nikon SE 8x32

8

10.8

87

49

5.7

282

15.4

123



Observing
M1 M78 observations
A few extended object comparisons are included here to give some indication of the ability of these instruments to deliver on low contrast objects.

M78 under mag 4.9-5.0 skies
Fujinon 10x50, M78 was immediately visible. Central stars are not seen.
Nikon Action 10x50, not easy but was seen OK.
Celestron Regal 8x42 roof, it was just barely seen
Could not find it in any binocular handheld.

M78 under mag 5.0-5.2 skies
Once I pinpointed its location, I could just barely detect it in 10x50s.
In a Nikon SE 10x42, M78 was easy.
Celestron Regal Roof 10x42 it was not easy but was seen OK.
Bushnell Legend 8x42 Roof, just barely seen
M78 seen in all, but with difficult at 7x and 8x.
Saw M78 in Bushnell handheld braced.
I did not see it at all in the 8x42 BFL.

M78 under mag 5.2-5.4 skies
Leupold WR Mesa 10x50, seen good,
Nikon AE 10x50, seen good,
Nikon Monarch ATB 10x42 Roof, also seen good.
Bushnell Legend 8x42 Roof, seen averted
Oberwerk 8x56 (8x48), just barely seen
Pentax PCF WP II 8x40, just barely seen


M1 under mag 4.9-5.0 skies
Fujinon 10x50, M1 was seen only after concerted effort and chart reference.
Nikon Action 10x50, took repeated tries to find it, even averted.
Celestron Regal 8x42 roof, took even more time and when I did suspect seeing it with averted vision, it was questionable.
Not seen in any handheld or braced.

M1 under mag 5.2 skies,
It was not seen at first. But after locating it in a 15x70, it was a bit easier to detect in the 10x50s. It was barely detected with great difficulty in the BFL 8x42.

M1 under sky mag 5.2-5.4
Oberwerk Mariner 8x40 (8x32) M1 barely seen
Pentax WPII 8x40 M1 barely seen
Nikon AE 8x40 M1 not seen
Nikon Action VII 8x40, M1 not seen





Front row: Nikon SE 8x32, Garrett Apo 8x42 roof
Second Row: Celestron Regal 8x42 roof, Oberwerk Mariner 8x40
Third row: Bushnell Legend 8x42 roof, Garrett Classic 8x45, Fujinon BFL 8x42
Back row: Nikon Action 8x40, Nikon Action Extreme 8x40, Pentax PCF WP II 8x40


Summary

Nikon Action 8x40 – 8x38, 8.15-deg, er=11mm, IPD=56-73, cf=11ft, fmc/fc
The Nikon Action has the widest fov 8.15-deg, has very good normal resolution, but has very poor boosted resolution. Outer fov sharpness is good to only 60% and deteriorates to poor by 65%, but that gives a 5.3-deg usable fov. It has no functioning internal baffles and is poorly blackened. However, it does illuminate the exit pupil very well and internal vignette is well controlled. Yet LM maximum is mag 9.1, possibly due to reduced contrast and less than optimum coatings. It is poor mechanically and ergonomically, with a wobbly eyepiece bridge and the shortest eye relief of 11mm. Mechanical build quality, very short eye relief, poor outer fov, lack of good baffles and slightly reduced aperture all lower the score on this one. It scores in the middle overall.


Garrett Classic 8x45 - 8x38, 7.3-deg, er=18mm, IPD=59-74, cf=15ft, fmc/fmc
The Garrett Classic looses significant points for the reduction of aperture. Resolution is the worst of the 8x binoculars. Delivery of light is unbalanced and has significant vignette, but the coatings and the exit pupil illumination are good. Field sharpness falls off immediately after 70% giving a net result 5.1-deg usable fov. IPD is limited to 59mm. Quick loss of field sharpness, significant reduction of aperture, significant vignette, and poor resolution move the total score to near the bottom of the list. Not recommended.

Oberwerk Mariner 8x40 – 8x32, 8.0-deg, er=16mm, IPD=62-73, cf 15ft, fmc/fmc
The Mariner is stopped down by internal baffles that have much too narrow an opening. The 8.0-deg fov makes it one of the widest, but it reaches sharp limt at 70% and falls off immediately afterwards. Usable fov of 70% means it has a 5.6-deg usable fov. Resolution is average and handheld resolution is very good. The Mariner scores well for lack of internal vignette high for illumination of the exit pupil. The low limiting magnitude results reflect significantly reduced aperture. Narrow limit IPD of 62mm is the worst of all binoculars. Due primarily to dramatic reduction in aperture and quick fall off of usable field, the Mariner scores are lowered. However, its still in the middle of the pack. Were it not for the dramatic reduction in aperture and the accompanying loss of illumination and LM, this binocular would score respectably in the average range of all 8x40s. Not recommended for children.

Oberwerk 8x56 - 8x48, 5.7-deg, er=21mm, IPD=59-72, cf=30ft, fmc/fc
This Oberwerk has the narrowest fov of all the 8s, 5.7-deg. The field is sharp to 75% but not usable beyond 75%. Usable fov is only 4.3-deg. It has one of the greatest amounts of aperture reduction due to mis-sized internals. It has significant internal vignette and poor illumination of the exit pupil. It has average normal resolution, but very poor boosted resolution. LM reflects the reduced aperture and vignette. Significant loss of points in almost every category places this one near the very bottom of the list. Not recommended.


Swift Ultralite 8x42 – 8x41, 6.5-deg, er=19mm, IPD=51-76, cf 20ft, fmc/fmc
It has good fov at 6.5-deg, sharp out to 75% and usable to 80% for a good net usable fov of 5.2-deg. Not waterproof. It has one of the widest ranges of IPD of all binoculars. Resolution is average, however handheld resolution is poor. There is internal vignette and light transfer is poor. The Swift loses most of its points for poor resolution and internal vignette. Still, overall score is average.

Pentax PCF WP II 8x40 – 8x39, 6.3-deg, er=13mm, IPD=57-74, cf 11ft, fmc/fmc
It has one of the highest percentages of sharp and usable field of view. 85% sharp, 95% usable, gives a 6.0-deg usable fov one of the widest measured. Has adjustable twist eyecups, focus lock. Coatings are very good, rank among the best. Resolution is excellent. It has issues with internal tilt and vignette, but illumination is good. LM is good. Mechanically very good. The Pentax loses points for vignette and narrow depth of field. A very good performer, it ranks near the top of the list. Recommended.

Bushnell Legend 8x42 Roof – 8.2x41, 6.5-deg, er=17mm, IPD=58-74, cf=7ft, fmc/fmc-p
The Bushnell is fast focus and weighs 25oz. I especially like the contoured shape of this binocular and found it to be one of the most comfortable handheld. Everything works easily and does what it is supposed to do, providing a wide range of adjustability for different users, although IPD could be tight for children. It has moderate marks for field sharpness, but it has the widest usable fov of the roofs next to the 8xRegal. Good coatings. Contrast was not as good as the Regal. It shows very good resolution and gave one of the highest marks for handheld resolution. The Bushnell may not be the best in any category, but it does a lot of things very well and doesn't do anything really poorly. Among all 8xs, recommended for both terrestrial or astronomy.

Garrett DCF 8x42 ApoRoof - 8x41, 6.7-deg, er=19mm, IPD=57-71, cf=5ft, fmc/fmc-p
Widest fov of all the roofs. no false color at all, bright image, one eyecup constantly changed position needed to reset it every time I used it. No pincushion at all, may reduce desirability for terrestrial use. Very compact, very comfortable to carry around. Has nice image and ample eye relief. All resolution values are good and shows little axial tilt and transmits internal beam well, indicating little internal prism vignette. Looses points for lack of wide sharp fov, low LM, loose eyecup and difficult diopter. Still a good performer. Except for the finicky eyecup, I enjoyed this one for terrestrial use. If I wanted to see the faintest stars, I'd pick another.

Celestron Regal 8x42 Roof - 8.1x42, 6.3-deg, er=17mm, IPD=58-74, cf=6ft, fmc/fmc-p
The 8x42 Regal has ample eye relief and coatings are among the best. The Regal 8x42 has almost no field curvature and has one of the widest usable field of view of any binocular in this entire study. It is slow focus at close range, but fast focus otherwise. The internal vignette test shows a perfectly balanced image with little to no vignette. Illumination is good. LM shows near equal to some of the best 10x50s. Resolution is excellent. The 8x42 Regal is an outstanding astronomy binocular for its ease of use at the eye, excellent contrast, deep limit and low aberration wide field. I suppose these are all attributes that would make it a good terrestrial binocular also.

Nikon Action Ex 8x40 - 8x39, 8.1-deg, er=14mm, IPD=56-73, cf=13ft, fmc/fc
The Nikon AE is sound mechanically and has good ergonomics. Normal resolution is excellent. Boosted resolution is OK, not one of the best. Handheld res is very good. The aperture shows only minor reduction. Coatings do not rank as the best. Internal vignette is very well controlled, exit pupil is balanced and illumination is excellent. There are no internal reflections. Limiting magnitude scores well. Outer field sharpness falls off at 60% out, and is fair only out to 65%, but that still gives a 5.3-deg usable fov. Curvature contributes to a very wide range of depth of field. Eye relief is sufficient at 14mm. There is no chance of hitting the well recessed eye lens with your eyeglasses. Eye cups are widely adjustable and IPD covers a wide range. Diopter is very easy to adjust. Overall, the Nikon AE scores the highest of the 8x40s, but not by much over the Pentax PCF WP II, Celestron Regal or Fujinon BFL. Each does some things slightly better than the other. Strongly recommended.




The Nikon Action Extreme 8x40, shown here with both the AE10x50 and AE12x50, has exactly the same prism housing and eyepiece assembly, except perhaps for eyepiece focal length. The major difference is it has smaller objective cones. This is similar with almost all families of binoculars and can be seen with the Garrett Classics, the Oberwerk Mariners and the Nikon SEs.




A few words about the benchmarks:

Nikon SE 10x42 - 10.2x42, 6.2-deg, er=17mm, IPD=53-74, cf=13ft, fmc/fmc,
Very light at 24oz. (680g). No false color noticed. Very little field aberration, but mild curvature. Quite comfortable handheld, ample eye relief, not as much blackout issues as the 12x50SE. Relatively fast focus 30m-100m, but slow focus 30m-3m. Interior baffles and blackening is excellent, no internal reflections. Reaches the same LM as the 10x42Regal, the deepest of the roofs and better than many 10x50s. Extended object contrast is superior, better than the 10xRegal. Measures near best in normal power on-axis resolution, 6x boosted resolution and handheld resolution. Nearly sharp to the edge, usable field of view about 90% fov. Not waterproof . Aperture is true 10x42 and system shows very good transfer of light beam. Coatings are among the best made.

Fujinon BFL 8x42 - 8x40, 6.5-deg, er=11mm, IPD=57-73, cf=14ft, fmc/fmc
Very light at 24oz. (680g). No false color at all, no field curvature at all, very light and comfortable, although it would be nice if eye relief were about 2-3mm longer. In the short range, they are faster focus than any of the roofs. Just barely enough eye relief for me to use with my eyeglasses. Very well baffled interior of objective tubes, no internal reflections. Has one of the best on-axis resolution marks but also they hold up to show some of the best 6x boosted resolution AND they exhibit some of the best outer field sharpness. Focuses stars to very fine pinpoints. These are waterproof, nitrogen purged, aluminum alloy construction. They have a lifetime warranty. Right eyepiece has a clickstop diopter adjustment, very positive. The 8x42BFL are very comfortable in the hand, and at the eye. Right up to the eye, quick to grab the view, easy and quick to focus.

Some of these roofs make excellent astronomy binoculars. The Celestron 8xRegal and the Bushnell Legend 8x42, are good choices. As a bonus, these choices equip the user with a nice lightweight piece that can be used for terrestrial use. The Nikon Action Extreme, the Fujinon BFL and the Pentax PCF WP II all score very high for the 8x porros. After that, the rest of the porros are quite a ways down the list. The Oberwerk 8x56 and then the Garrett Classic 8x45 scored 2nd and 3rd from the bottom of the entire list of 34 binoculars tested.

Clear skies, and if not, Cloudy Nights
edz

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