Of course, my birding and optics testing friends in the far north (Finland) take exception to that remark. In the low light levels they have to deal with, they still see definite advantages in a big objective—the bigger, within reason, the better.
In theory, of course, a larger objective should result in an image with higher resolution (detail) and brightness. Of course, we want an image with all the detail we can get, right up to the limits of what the human eye can see. We humans, birders in particular, delight in detail, even at close ranges, when our scopes turn into long range microscopes, delivering more detail than we could see with the unaided human eye. Brightness, which varies with the amount of light energy in the image, increases the amount of detail we can see, but it also brings out the color. The reason color becomes muted in twilight, and all but disappears in darkness, is that the cones of the eye, the cell structures which receive the color information, are “light hungry.” They take considerably more energy to activate than the rods which pick up the structural detail of the image. Since color is so important to birders, a brighter scope should be a real advantage in the field.
Of course, there are practical limits to the size you can make the objective. How large an object are you willing to carry around all day? How heavy a tripod are you willing to carry to support it?
A larger objective
means a larger scope—not only bigger around to accommodate
the larger glass, but, considering the limits of optical design, also longer.
Because of the physics of the way glass bends light, longer focal length objectives
have less optical problems than shorter objectives of the same diameter, and
are therefore, easier to design. The “fast” optical system (one with
a large diameter objective and a short focal length) necessary for any spotting
scope is stretching the limits of what you can do with glass—hense the
popularity these days of exotic glass mixes and elements (ED and Fluorite) in
spotting scope objectives—and when you increase the size of the objective,
the problems become that much more difficult to deal with.
Therefore, designing a high quality, compact 80 mm spotting scope, or, worse,
a compact 85 mm spotting scope, is a real challenge.
Swarovski and Zeiss have accepted the challenge, taking what they learned,
we would think, the the design of the 65s and producing scaled up versions.
Swarovski makes the new 80 mm scope in traditional glass, ED glass, and in
both straight through and offset models. They are pitching, for what I feel
are good
reasons, the ED, offset model particularly to birders, and that is the model
I have for testing.
It is clearly a scaled up version of the 65. Physically the two
scopes couldn’t
look more alike. In fact, it appears as though Swarovski simply took the back
end—prism housing, lens mount, focus barrel, tripod mount, etc.—from
the 65 and grafted on an 80 front end. The result is a scope that is not much
larger, in fact, than the 65. It is not significantly longer (just over an
inch) and the extra flare to accommodate the big objective manages to maintain
something
like the compact profile of the 65.
The real difference is in weight. The 80 is just under 10 ounces heavier. That
doesn’t sound like much, and it isn’t at the beginning of 2 mile
hike along the beach or the dike. By the end of the hike it is significant.
The larger objective also effects balance. The 65 is noticeably back heavy.
The 80 hangs almost level from the tripod socket. (See the illustration below.)
How the weigh distribution effects
performance on a tripod head depends largely on the head and tripod in question.
In my experience, the 80 is more difficult for most tripods to handle, and
requires a considerably heavier tripod for a stable image.
Optically, the 80 is, as you would expect, noticeably brighter in anything but full daylight than the 65. Swarovski has managed to do a very good job of designing a fast objective. Resolution is everything you would expect, and it is sharp, with the excellent Swarovski eyepieces, right out to the edge of the field. As with the 65, the view is exceptionally contrasty, and holds brightness and contrast exceptionally well as light levels fall off.
(For a birding story from the introduction of the new Swarovski 80 mm in Pamplona, Spain go to Wild Country.)
Zeiss has taken
the “bigger has got to be better” philosophy to
heart. The 85 mm Diascope is an impressive piece of glass. Essentially they
used the
same tactic as Swarovski, grafting that 85 mm objective to the same back end
that the 65 mm Diascope uses. That, of course, means that they share the intelligently
designed dual ratio focus control. Again, the larger objective effects balance
on the tripod, in this case making the Diascope considerably front heavy. Front
heavy is the least desirable configuration on any tripod as it means that the
scope is going to crash its objective against the tripod leg when you forget
to set the head, and that extra weight in the front seems to make it more difficult
for most tripods to stabilize the view.
Again, as expected, the Zeiss 85 is noticeably brighter, in marginal light, than the both their own 65 and the Swarovski 80. As with the 65-65 comparison, the Zeiss appears to be brighter in identical light, but somewhat less contrasty than the Swarovski. Resolution, again, is all you would expect, though, with the Zeiss eyepieces, edge sharpness is not as good as the Swarovski manages.
Which brings us to a notable point: to my eye, the Swarovski eyepieces are just a shade better then the corresponding Zeiss offerings at most powers: with higher contrast, better edge sharpness, and roughly equivalent fields of view. Swarovski introduced a 45X wide field eyepiece at the same time as the 80 mm scope that is, as far as I am concerned, just about the ideal day-in, day-out birding eyepiece for those who resist a zoom. (I really like the functional, tethered, lens caps on the Swarovski eyepieces as well.)
So, if I had to choose between the Swarovski 80 and Zeiss 85? The Swarovski has, in my opinion, the edge in field-worthiness, with its ultra rugged armor, fast helical focus, excellent balance, and slightly more compact body. The Zeiss is brighter in most situations, and delivers more detail (higher resolution) in all situations. As light levels fall, the scopes’ optical performances approach each other more closely, with the extra contrast of the Swarovski offsetting the extra diameter of the Zeiss.
I don’t
know. To me it is a toss up. If I were shopping for a top of the line, no-holds-bared,
80-85 mm spotting scope, I would be hard pressed
to choose
between the two. It might, in the end, come down to price, and how friendly
the dealers were. This is one of those situations (increasingly common in our
current
optics market today) when you really can not go wrong. Either of these scopes
will give you state-of-the-art optical performance, in a package that is as
compact
and lightweight as modern industrial design can make it. These big scopes are
everything their little siblings are and more: the ulitmate in fail-safe birding.
Both Swarovski and Zeiss deserve a lot of credit for taking the particular
needs
of field
birders
to heart,
and delivering products that will maximize our enjoyment of our days in the
field, and every bird we see.
Will the current (and I hope “coming”) crop of 65’s kill off the 80 mm class scope? I might have said so (did say so!) before the introduction of these compact 80 and 85 mm scopes from Swarovski and Zeiss. Big scopes, for better or worse, are back in the game.
Of course, the operative phrase above (you might have noticed it) would be if I were shopping for a big scope. Let me tell you a story.
I took the
Swarovski 65 and 80 and the Zeiss 85 out one late afternoon and kept them
out until full dark, just to see what advantage there might be to
a larger
objective. Understand, I am undoubtedly biased in this matter, since I have
already stated my preference for a more compact scope, and my willingness
to trade some
optical performance for a scope and tripod package that I can carry all day
in the field when I have to.
I set the scopes up next to each other looking out across the mouth of a small tidal river toward a lager tidal river where gulls and mergansers were settling in for the night. As the sun set and the light fell, I was busy moving from eyepiece to eyepiece, checking the amount of detail and color I could see through each scope. My conclusion? Nothing unexpected. In direct comparison, the 85 was noticeably the brightest in all light levels. The 80 was next. The 65 last. The amount of difference between the three was most noticeable when moving from the 85 to 65. The difference between the 85 and 80 was barely perceptible. The difference between the 80 and 65 was more noticeable but still very small. As light levels fell, as you probably gathered from the discussion above, the 85 and 80 seemed to draw closer together. Both still held an edge over the 65. However, at no time did either of the big scopes show me something I could not see in the 65. It was easier to see both detail and color through the 85 and 80, right out to full dark, but the same detail and color was there in the 65, you just had to look harder to see it. I am also convinced, that the only way to see the difference between the scopes in low light is to compare them side by side. In any light, right down to extinction, any of these scopes would provide what most birders would consider satisfying performance. In low light I might wonder if a larger scope would show me more, but, after this test, I remain unconvinced that it would.
Finally, on this years’ unofficial family Christmas Bird Count along our coast here, I packed all three scopes in the back of the car (along with the Tele Vue 75mm APO). I thought I might see something far off shore that would make me regret not having a larger scope. I started out carrying the Swarovski 65 mm on a light weight Manfoto Junior Tripod, and, even when we got back to our final stop in deep twilight to hike once more over the dunes for a last look out to sea, I was not tempted to take a larger scope. Maybe I should say, especially by that last stop, after carrying even the relatively light 65 and tripod all day, I was not tempted by anything that weighed more. Did I miss anything? I don’t think so.
Still that is a difficult conclusion to convince most birders of, and apparently an impossible conclusion as far as our Finnish friends are concerned. Given the bigger-has-got-to-be-better attitude, I figure there is still a strong future in 80 and 85 mm scopes.