From: BUNNER@MACC.WISC.EDU (Dana A. Bunner)
Subject: Review of 10X Binoculars (long)
Date: 5 Jun 1995 21:41:06 GMT

Version 1.3

The following is a moderately-deep review of six 10X binoculars along with
some briefer comments on a few other models.  Tests were performed at Eagle
Optics by myself (these opinions represent only my own and are not the
opinions of Eagle Optics or their staff).  My thanks to E.O. for allowing
me to spend nearly two hours at their counter playing with up to 10
binoculars at a time.
 
Tests performed included:
 
Sharpness/Image Resolution - A resolution chart consisting of several line
patterns, ranging from wide to very fine, was mounted on a wall at
approximately 60'.  I moved the image from side to side and top to bottom
to observe sharpness from the center to the edge of the field.
 
Depth of Field (DOF):  When focused on images at varying distances, I made
note of the depth of the focused image.  More depth of field lessens the
need to refocus and adds more of a 3-D perspective to an image.  I consider
this to be an important factor when in the field.
 
Field of View (FOV):  Standard observance of the width of field shown.
 
Eye Relief (ER):  Did they have sufficient E.R. to accommodate eye/sunglass
wearers.
 
Close Focus:  How close could I get to an object and still achieve a sharp
focus.
 
Contrast:  I did check on several models to see if a bright background
induced a loss of contrast on the rest of the viewable image.
 
Focus Adjustment Range:  I have very bad eyes (-7.75 diopters), so I need
to use glasses all of the time.  However there are times when I am
observing still objects where I enjoy taking off my glasses to get a bit
better view (eliminates two glass surfaces and I can block out sunlight (or
headlights at night) with the rolled-out eyecups.  Many binoculars cannot
be adjusted to give me a sharp focus at infinity given my atypical eyes.
 
I hope to continue my tests by testing for chromatic aberration and a more
rigid test for contrast, but they were closing the store before I could get
to those tests.  I did a minor check with a few models by using an in-store
spotlight, but I would rather test bright outdoor images.
 
Models tested (and approximate prices & weights):
  
 Celestron Ultima 10x42           $220    21-22 oz.
 Celestron Ultima 10x50           $230    26 oz.
 Celestron ED 9.5x44              $380    26 oz.
 Nikon  10x35E                    $320    23 oz.
 Optolyth Alpin 10x50             $380    23-24 oz.
 Swift Audubon 10x50              $220    31-32 oz.
 
Models "mini-reviewed"
 
 Bausch & Lomb Discoverer 10x42   $590    29 oz.
 Bausch & Lomb Custom 10x40       $290    28 oz.
 Kowa 10x40                       $190    low 20's.
 Nikon Execulite II 10x40         $410    24.5 oz.
 Swift Ultralight 10x42           $200    21 oz. 
 

     ** Reviews **
 
Celestron Ultima 10x42:  Center of field sharpness was above-average for
$200 price range but next to last in this group.  Off-center sharpness also
above-average, lense-edge sharpness slightly below average.  Good FOV, one
of the widest in group & about the same as the Nikon 10x35E,  good
depth of field.  ER was a bit less than needed for full FOV through
glasses.  Contrast was good. Overall, I didn't like the Ultima 10x42 as
well as the Ultima 7x42 or 8x42 models, which I feel are excellent values.
But I still haven't found any better 10x40-42mm for under $200.
 
Celestron Ultima 10x50:  Center of field sharpness was very good, off-center
sharpness also good, lense-edge sharpness was average.  FOV was narrower
(almost 100' narrower at 1000 yards than the wide-angle Swift 10x50, and
about 170' narrower than the popular Swift Audubon 8.5x44).  Depth of field
was average. ER was excellent.  Close focus was below average, almost 25'.
Contrast was very good.  I was not able to focus w/o glasses to beyond 50'. It
was obvious that this design emphasized image sharpness and eye relief at
the expense of FOV and close focus.  Thus the purchaser needs to determine
their usage/priorities before selection these, if one doesn't require a
wide FOV or up-close focusing, then these are an excellent value.  The wide
center-of-field sharp images were the best I've seen in a sub-$300 binocular
and the rival of $500 models.  And it was my impression that these gave
the brightest image in the entire group.
 
Celestron ED 9.5x44:  Center of field sharpness was very good, off-center
was good, lense-edge was above average.  Moderately good FOV.  Eye Relief was
marginally adequate for eyeglasses, Celestron specs 16mm but I perceived
the actual number to be slightly below this, perhaps around 14mm.  Very
good depth of field.  Images had excellent clarity and color, the most
natural color of any binocular I've used.  Close focus was good, I was able
to focus to about 12'6".  Contrast was very good. Focusing w/o glasses was
poor.  Overall a very good binocular and over the center 2/3 of the image
comparable to $700-800 binoculars.
 
Nikon 10x35E:  Center of field sharpness was very good, off-center good,
lense-edge above average.  Overall image resolution was a close 2nd best in
the group.  Good FOV for a 10x (which is to say that it would be below
average for a 7x).  Eye Relief was just a bit short of optimal for eyeglass
wearer, but still very usable.  Good depth of field.  Close focus was only
a few inches back of the Celestron ED.  As with most of the models in this
test, contrast was good.  I was able to achieve sharp focus without wearing
eyeglasses.  The smaller exit pupil (3.5mm) did make it a bit more
difficult to align with my eyes when wearing glasses, I had to slide them
around a bit and I wasn't able to align them as quickly, which might be a
problem if I were wearing them around my neck and wanted to see a fast
moving object.  Overall a very nice, small, sharp, lightweight binocular
with decent FOV and close focus specs.
 
Optolyth Alpin 10x50:  Center of field sharpness was very good with a wide
"sweet spot."  Off-center was very good, lense-edge sharpness was good with
only a slight amount of fuzziness.  I rank them as best in the group for 
sharpness.  FOV is narrow, almost exactly the same as the Celestron Ultima 
10x50.  Eye Relief was excellent.
Depth of field was good, ranking in the middle of the group.  Close focus
was average, somewhere around 18-19'.  Contrast was very good, particularly
under sunlight (but see below on coatings). Focusing w/o eyeglasses was
very good.  They were extraordinarily lightweight for a rubber-coated 50mm.
Image color and brightness was slightly subdued, Optolyth's "Ceralin"
coating is claimed to reduce haze and glare under bright sun, but it
appears to slightly impact visible light.  Colors were just a touch
"warmer" with a hint of yellow.  There was a very slight loss in brightness.
The basic design is essentially the same as the Ultima 10x50, stressing
image sharpness and eye relief over FOV and close focus, however it is
better than the Ultima in all respects.  It is left to the individual
purchaser to decide if the difference is worth $150.
 
Swift Audubon 10x50:  Center of field sharpness is good, off-center is
fairly good but degrades a bit before you get to the edge.  Lense-edge is a
bit below average.  FOV is best in group, approaching that of many standard
7X designs.  Eye Relief was somewhat short for eyeglasses at 10mm, however
since the FOV is so wide, an eyeglass wearer still gets a fairly wide view
even with the short ER.  Depth of Field was very good.  Close focus was good
for a 10x50 at around 16'. Contrast was a bit below group average but still
quite acceptable. Focusing w/o glasses was just short of getting a sharp
focus, should be plenty for most people.  The Swift's are a bit shorter and
fatter than other 10x50's, due to their wide field design & larger prizms.
 
    ** Mini-Reviews **
 
B&L Discoverer 10x42:  Very good center of field sharpness, good depth of
field, good FOV for a 10x.  ER seemed okay, and they are spec'ed for a good
close focus number, however I did not complete these tests due to the
off-center image resolution being so poor that I eliminated them from
consideration.  They were the worst of this entire group by a considerable
margin on off-center sharpness.  [Note:  The 7x42 Discoverer was a much
better binocular and I would give it serious consideration for a 7X.]

Bausch & Lomb Custom 10x40:  Good image sharpness, in fact much better than
its more expensive Discoverer sibling.  Not as bright as the 50mm models
in the group but good for a 40mm.  Field of View was fairly narrow at 273'.
But it had pretty good figures for close focus.  The mechanics were pretty
stiff in all three B&L Customs I tested.  Good Eye Relief.  Did not open as
wide as many others, but still far more than needed for the average person.
Seems a reasonable purchase for the money but not an outstanding buy.
 
Kowa 10x40:  These are brand-new models.  They are very light, due to using
magnesium bodies.  They handle well and have a nice rubber coating.  They
had good sharpness in the center of field, falling off as one moves
off-center to being quite poor on the lense-edge.  Eye Relief was good (it
was excellent on the 7x40 model).  Depth of Field was average for this
group.  Contrast wasn't up to others in this group.  I thought they looked
and handled better than they performed.  Least expensive model tested.
 
Nikon Execulite II 10x40:  Good image resolution, would rank in upper half
of this group, but not quite as sharp as Nikon 10x35E.  Image brightness
was below average, there were significant differences in the image
brightness of this model as compared to the Celestron Ultima 10x50 and ED
9.5x44, and in a direct comparison (swapping back and forth several times
quickly) the B&L Custom 40mm was perceptibly brighter.   Eye Relief
was a bit less than optimal for eyeglass wearers, despite Nikon's claims
of 15mm.  Lightweight of 24-24.5 ounces was nice.  They also had a nice
rubber-coating.  FOV was average for this group.  Depth of Field was below
average.  Performance didn't quite match price, IMHO.  Would not recommend
for low-light usage.

Swift Ultralight 10x42:  Very similar to Celestron Ultima 10x42 in both
style, specifications, and performance.  Light weight and rubber coatings make 
it easy to handle in the field.  Images are bright and contrast is good,
but overall image sharpness is average.  The 8x42 model in this same series
gives sharper views. 
 
Overall conclusions:
 
There is no one best binocular in the group.  All of them compromised in
some areas in order to perform better in others.  My three favorites were the
Optolyth Alpin 10x50, Celestron ED 9.5x44, and Nikon 10x35E.  On the
lower-priced end of the scale, the Celestron Ultima 10x50 and Swift Audubon
10x50 give buyers nice options depending on their needs.  The B&L Custom
10x40 is also worth consideration.
 
The Optolyth would be excellent for astronomy, or medium-to-long range
observation where wide fields are not needed.  Good low-light performer.

If you can't quite afford the Optolyth but your primary desire is good
sharpness across the entire field, then the B&L Custom is an option.  
However it is more of a birding glass (40mm, good close focus) and thus
not a great choice for astronomy.  FOV is narrow, like the Optolyth.
 
The Celestron ED has wonderful clarity and color and good sharpness but
just average field of view.  Would be very nice in twilight/early
morning sessions.  This would be my choice for best all-around performer
in the group, but others might fit your individual needs/perferences better.
 
The Nikon E-series is quite sharp and has a good field of view for a 10X.
A very nice 10X birding glass under well-lit conditions, but noticably
dimmer than the ED and 50mm models in low-light.

And if you only have around $200 to spend and would like a capable glass
with a decent FOV, then the Swift Ultralight and Celeston Ultimate are the
best choices.  But neither have enough eye relief for eyeglass wearers.
 
I hope to add a few more models to this group, such as the new Burris 10x50
that has some promising specifications (450'+ FOV, 17mm E.R., and
close focus of under 15' to name three).  Hard to imagine they will be
able to deliver all of this and sharp optics too.

Also only one model in the entire group above is waterproof, the B&L 
Discoverer 10x42 [which I didn't like, but I do like the 7x42 in the same
series.].  I do hope to review the Fujinon 10x42 SHS at some point.  And
maybe a Steiner. (But I haven't been impressed by Steiner's in the past.  I
once had a chance to buy one at 50% off and decided to pass on the deal 
after testing it.  But those tests were conducted too long ago to include
in this summary.)

Dana Bunner