Nikon Diplomat 8X23

We reviewed the new Nikon 10X25 Diplomat in the last issue of BVD. The Diplomat series has the distinction of being the first binoculars to use (or at least to advertise the use of) aspheric lens elements.

A traditional lens, no matter how high quality it is, simply can not bring all the rays of light that strike it to exactly the same focus. It is a simple matter of geometry. The lens surfaces are segments of a sphere and the rays from the edge of a spherical lens focus at a different distance from the lens than the rays from the center do. The defect is called spherical aberration, and it has plagued lens designers from optical day one. The only solution is to make one or more of the lens elements "aspherical" (not a sphere) by exactly the right amount to cancel out the aberrations introduced by the other elements. So why, you might ask, do optical designers and lens makers continue to make spherical lenses? The answer is simple. A spherical lens is easy to make. Any other shape or curve is very difficult. In fact, spherical lenses practically make themselves. Simply rub two pieces of glass together so that they overlap at the edges with some grit between them and, in time, you will grind two relatively perfect spherical surfaces, one concave and one convex. That fact is the basis of the whole lens maker's art. Aspheric surfaces require a great deal of delicate hand grinding, or incredibly sophisticated machines, either of which equals lots of money. Consequently they aren't in regular use in consumer optics.

Until now that is. Nikon's Diplomats use at least one aspheric element to almost completely remove spherical aberration from the center of the field. It examining and testing the binoculars this seems to have two effects. It makes the image seem brighter, and it increases resolution to the point where these small binoculars closely approach the theoretical limits for their respective objective sizes. The apparent brightness is probably a result of having all the energy from any given point in the scene focused at the same point in the image. This, of course, increases the apparent brightness of given points, but it also means that less light is scattered to wash out adjacent points and the overall contrast of the image is increased. In the field the 8X23 Diplomats give the impression of being as bright as binoculars twice their size. Only actual, direct, side by side, comparison with, say, a pair of 7X35s will show a difference in brightness. The 8X23s are certainly very bright for their size and bright enough for almost any field condition. The fact that all lens elements are fully multicoated also adds to the apparent brightness and contrast.

The increase in apparent (and real) resolution in the center of the field has to be seen to be appreciated. The center half of the field is as sharp as, shows as much feather detail as, binoculars with objectives at least twice as large. Compact objectives generally show their limitations most clearly as distance increases. The image provided by the 8X23 Diplomats, however, holds up at distance as well as, or better than, some of the finest full sized binoculars on the market. Again, it has to be seen to be believed.

On the other hand, the outer half of the field, especially in comparison to the extreme sharpness of the center, is quite fuzzy. It is not curvature of field (when the center of the field is in focus at a different point than the edges), a flaw that afflicts some other binoculars (even some very expensive binoculars). Objects at the field edge can not be brought into sharp focus no matter how you rack the knob back and forth. There is also a subtle fun house mirror effect at the edge of the field that makes panning with the Diplomats somewhat disconcerting at first.

How important is the fuzzy edge? We birders automatically center on the bird we are interested in. The edges of the field are used mainly to detect movement that might be something we would like to look at, and to follow a bird then it takes flight. The 8X23 Diplomats have a wide enough field overall, and large enough "zone of sharpness" at the center to make them very satisfying in the field. In fact, in actual field use, you are not likely to notice the fuzziness at the edge unless you are really looking for it.

The Diplomat's other features are on par with the optics. The body is excellently shaped and the rubber armor is both attractive and easy on the hands. The locking diopter adjustment ring is among the best I have seen. The focus knob is large for a compact and very easy to use. The extreme light weight, along with an excellent strap, make them a joy to have around your neck in the field. The only failing is a lack of anti-reflective coloring around the objectives -- the gray insides of the lens barrels catch too much light and throw it up into the lenses, reducing contrast in some situations. (If I bought a pair of these, the first thing I would do is blacken the offending parts.)

The 8X23s are still compacts, with many of the drawbacks of compacts in general that we covered in the last issue. No compact is ever going to give you as easy a view as full sized binoculars. You have to center your eyes very carefully behind the binoculars and focus very precisely, but once you get centered and focused, the Diplomats certainly deliver.

I was, of course, very interested in comparing the new Nikon 8X23s directly to the current Reference Standard for compacts, the Bausch and Lomb 7X26 Customs. If ease of use is your major criteria, the Customs still have a distinct edge, with their wider field, longer eye-relief, and more forgiving exit pupil size. They are also somewhat less expensive. There is no doubt, however, that you will see more detail, and detail at greater distances, with the Nikons. The Customs are excellent compact binoculars, but once you have seen the extra clarity and definition provided by the Nikons when viewing the same bird under identical field conditions, it is hard to go back to the Custom view. Given the excellence of both the optics and the handling features, the Nikon 8X23 Diplomats become the new Reference Standard for compact binoculars. (Bausch and Lomb will release a redesigned Custom compact this summer -- watch for a review in a future issue.)

As good as the Diplomats are, there are times when I would still want the never fail, get the id anywhere/anytime, surety of full sized binoculars like the Swift Audubon 8.5X44s, or even and exceptional pair of mid-sized binoculars like the Leica 8X32 Ultras (both covered elsewhere in this issue). There would be times when I expected to be in the field long enough and have the binoculars at my eyes often enough, so that ease of view would outweigh ease of carry and hold. CBCs, breeding bird counts, my first trip to Atu island or the Everglades -- you get the idea. Would you miss any ids (or any enjoyment of the birds) if you only carried the Diplomats. I seriously doubt it! But still, it's a risk I, for one, probably would not take.

The 8X23s are certainly superior binoculars, representing the current state of the art for compacts, but now, Nikon (or anyone else for that matter), what about using this same technology (including both the aspheric lens elements and the inverted porroprism design) to produce a waterproof (or at least shower proof), wide field, long eyerelief, 8X32-35 binoculars weighing something like 20 ounces? You could call the Ultimate Birder, even the BVD Ultimate Birder, and I, for one, would not argue with you (there will be a small royalty for the use of the name, of course). I have a feeling that we have only seen the beginnings of the commercial use of aspheric lens elements. It will be interesting to see just what kind of Better View develops!