The main reason that more people don't regularly carry a scope into the field with them has to be the extra weight and bulk. A scope is simply a hassle, no matter how you carry it, and for the few times you really need it , it is easy to convince yourself you don't really need it. Of course, as we pointed out in the August Seasoned Eye, a scope does more than bring in those marginal and impossible identifications. It provides a view of birds that can simply be had no other way. With a scope you can readily and regularly have a bird-in-the-hand experience--you can see every pin feather, every subtle detail of the amazing structure of these amazing bundles of life. Then too, there is simply nothing to compare to a scope if you want to introduce others to birding, or share your delight in a particular bird with the other's in your party. Given a cooperative bird, the view through a scope can make an instant convert out of someone who might struggle with binoculars for months without ever catching the fever. There is no doubt that a scope, carried regularly, will increase your enjoyment of time in the field, if, and this is a big if , the pain of carrying it doesn't completely offset the pleasure of using it.
For that reason I am always interested in compact scopes. Leupold continues to advertise their 60mm variable 12-40X compact scope heavily in the birding press, and it has evidently sparked quite a bit of interest, if you go by the number of calls I have had asking what I think of it. So, here it is...
First, it is indeed compact. At just over 1 1/2 pounds, it is
lighter than all but the lightest competing 60mm scopes (there are
binoculars that weigh almost that much) and its folded optical system
compresses the length of a full sized scope into under a foot.
Slipped into its cloth zip up pouch it can easily be carried over the
shoulder. At 12 to 20X you could even hand hold it for reasonable
views. It really comes into its own, though, mounted on a light
weight shoulder stock. So mounted it is quite usable up to its
maximum 40 power, and gives very steady views at 20X. If the focus
mechanism were not a bit tight and difficult to turn (probably due to
the necessary seals for complete waterproofing), the scope would be a
complete joy on a shoulder mount.
Optically, the system appears to use two mirrors to fold the light
path, and an extra set of lenses that turn the image right side up
and right way round. The variable power (zoom) is a built in benefit
of the lens erecting system. All you have to do is move the erecting
lenses forward or backward to change the magnification of the system.
Another advantage of the system is that, properly designed, it
provides exceptional eyerelief, and a decent field of view, at all
powers. On the down side, lens erecting systems are not known for
their optical quality. The extra lenses often degrade the image,
especially at high power, and, if the moving elements are not kept in
perfect alignment as they move, the image will be degraded further at
various, often unpredictable, spots in the power range. Add the fact
that the two large mirrors in the system should cause some light
loss, and, if not precisely made, their own image degrading effects,
and you have a real challenge for the optical designer and
manufacturer.
Leupold has pulled it off very well. The image is not as contrasty as the best of the 60mm scopes, but, due to the use of enhanced mirror coatings, it is just as bright. The huge eyepiece yields eyerelief that may in fact be too long for some users--I folded the eyecup down only half way for use with my glasses. Field of view is comparable to other high quality zoom scopes at similar powers. Resolution, at all powers, is quite good. In direct comparison to the best of the 60mm scopes (Nikon Fieldscope ED, the current Reference Standard), the image in the Leupold is lower in contrast, and not quite as sharp at any power, but it is, in my opinion, very usable, if your primary consideration is portability.
That last says it all. This is a very portable, very durable, very weatherproof scope, and that is a combination of features that is hard to match in any other scope currently on the market. If your primary interest in a scope is the sharpest, brightest, snappiest view of birds at all distances, or especially at higher powers--then you can find 60mm scopes that will give you just slightly better performance than the Leupold. If you want a scope to carry with you all the time, to mount on a shoulder stock, to pack in the corner of a backpack on a long outing, to be there whenever you need it and provide a decent view of distant birds at 12 to 40X--the Leupold variable just might be the one for you.
Considering its unique blend of features, I am giving the Leupold a Product of Special Merit classification in the Reference Set.
In response to a first draft of the review of the Leupold compact scope, I had a call and a letter from Forrest Babcock, the project engineer who oversaw the design of the scope. Besides correcting some terminology in my review, he wanted to make these points:
"The erector system is used to vary the magnification as well as invert the image formed by the objective. The unique aspect of using a lens erecting system as compared to a prism erecting system is that one can design it with nearly unlimited eyerelief. The lens erector system can be designed to provide diffraction limited resolution as well as minimal light loss if each air to glass surface is multilayer coated as is done on the Leupold variable spotting scope. The drawback of the lens erecting system is that the optical path length is much longer than the prism erecting system. After study of a considerable number of optical systems, Leupold determined that the only way to get high resolution as well as compact scope length would be to fold a relatively long optical system using high efficiency enhanced coatings on two fold mirrors. Development of the housing to precisely locate the mirrors at the correct angle was very difficult. However we determined the required tolerances and worked out a process to manufacturer the system to maintain the diffraction limited performance of a folded optical system.
"During development of the scope we used a computer program to determine the tolerance of every surface from the objective to the erector to the eyepiece to specify allowable deviations. This effort allows the scope to be manufactured such that no specific area of the scope contributes to image degradation beyond the diffraction limit of the 60mm objective. Part of the tolerance analysis included allowable misalignments of the moving erector cluster as required to vary the magnification. Leupold has acquired much experience in this area from years of building highly accurate variable power rifle scopes."
He also confirmed that the stiffness I noted in the focus mechanism is, they feel, an unavoidable consequence of the complete waterproofing, and offered the opinion that the difference in resolution I see when the Leupold scope is compared to the Nikon Fieldscope is the result of the Nikon's use of ED glass to better correct for chromatic aberration. He concludes:
"Thank you for the opportunity to discuss some of the attributes of our spotting scope, which I personally believe to be an excellent product which has very little sacrifice to optical performance for a great advantage of portability and eyerelief."
I can agree with that--hence the Product of Special Merit award in
the Reference Set.