Docter Aspherical Roof Prisms



Features chart
If you will remember, I was so impressed with the Nikon Aspheric compacts that I could hardly wait until someone applied the technology to a full sized glass. I predicted at the time, and continue in my belief, that aspheric technology, as it is perfected and brought to the mass market, will represent the next great leap forward for birding optics.
Well, the first full sized aspherics are here. Docter Optic is well known in Europe, where its products are routinely ranked with Zeiss, Leica, and Swarovski. They have only recently established an official US presence, but they are off to a strong start with the introduction of these two aspheric models.

There are many optical problems you can attack using aspheric technology. Nikon apparently optimized the design of their compacts for overall brightness and center field resolution, at the cost of some fuzziness at the field edge. Doctor has used aspheric technology to produce binoculars with what we might call uniform resolution across the field. The Docters equal the center field resolution of the best of the premium roof prism models and maintain something very close to that resolution right out to the edges of the field. This gives them a very open, easy view...with very little of the peep-hole feeling that some binoculars give you. In fact I would rank their ease of view right up there with the best...the Zeiss 7x42s, Swift Audubon 8.5x44s and the Leica 8x32 Ultras. This is especially noticeable in the 10x model, where you expect a more difficult view. Using the dollar bill test outlined in the last issue of BVD, the Doctors don't quite equal the step 2 distance for the best in their class, but their performance is certainly excellent. The only place the Docters fall short, optically, is in brightness. In direct comparison, neither appear as bright as comparable roof prisms (the Swarovski 10x42 and the Leica 8x32), and they are noticeably dimmer than porros in the same class. Despite that, their performance in low light is excellent. I have noticed this apparent contradiction in several other European glasses and can only conclude that the coatings used in Europe are designed to be most efficient at the lower light levels common there.

The aspherics have quite wide fields for their powers and eye relief that is just right for me with my spectacles. I can see the full field, without having to be extra careful about placing the binoculars precisely in front of my eyes (which, of course, contributes to both ease of use and ease of view). The rubber eyecups are sculpted to exclude light from the side of the eye when in the up position, a welcome touch, but fold down easily and well for use with spectacles.
Both units are quite compact and the 10x model is very light when compared to other roof prisms in the same class. The exterior is a matte rubber-like compound, with ribbing under the fingers, that is exceptionally easy to hold. Focus placement, at the center of the hinge, is easy to use, though some may find the control on the small size, especially with gloves in cold weather. It is a split ring control, with the individual eyepiece adjustment built in. Because of the design, setting the individual eyepiece adjustment is a chore...but once set, it holds very well.
These are not fully waterproof glasses, but they do have internal focusing, and appear quite well sealed. I had no trouble with them in ordinary use in extreme cold and wet...they never fogged up on the inside as some binoculars do...but I would be cautious about dunking them directly in water.

Docter has taken what amounts to a conservative approach to aspheric technology. They have produced truly bird-worthy binoculars in the process, without, however, achieving the kind of spectacular results I had hoped to see in full sized aspheric glasses.

Still, these are certainly fine binoculars. I would be happy to own and use either as my primary birding glass. Because Docter is new to the American market they are often available at somewhat less than comparable roofs from the better known European houses. The 8x32s, in particular, are close enough to the performance of the current BVD Best Overall Birding Binoculars (the Leica 8x32s) to make them worth a long hard look. The 10x40s should appeal to people who have always been impressed by the Zeiss 10x40s. They may, in fact, have an overall easier view, and, if memory serves me right, are somewhat lighter.

The Docter aspherics break no new ground, but they are truly bird-worthy roof prisms and may be available at a bargain price. When you come to think of it, maybe that's spectacular enough!



Docter aspherics10x408x32
resolution4.5 arc sec.5.1 arc sec.
dollar bill test distance21.5 ft.19.5 ft.
field of view6° (315ft@1000yds)7.4° (388ft@1000yds)
close focus20 ft.16 ft.
contrastexcellentexcellent
image qualityexcellentexcellent
brightnessvery goodvery good
eye relief15mm15mm
weight26.5 oz24.5 oz
height6 in5 in
focus easevery goodvery good
balanceexcellentexcellent
weather sealingvery goodvery good