Binoculars review

Alpen Optics Teton 10x50

Alpen Optics Teton 10x50
17 February 2010
The second Alpen Optics series of binoculars, falling in below only the Rainiers with regard to price and quality, is the Teton series. In consists of four roof-prism models with the following parameters: 8x42, 10x42, 8.5x50 and 10x50. Like in the case of the Rainiers, they are produced in Japan. They feature the same SHR metallic coatings put on the reflective surface of Schmidt-Pechan prisms to ensure high transmission. Additionally, on the prisms there is PXA phase correction and multi-layer coatings on all air-to-glass surfaces. The prisms are made of BaK-4 glass.

The Teton series have the optical system from the main Rainier series but the housing construction was taken from the lower Apex series.

The binoculars are sold in a stylish case, with an additional leather holder and a comfortable wide strap. Like all the other Alpen Optics models, the Tetons come with a lifetime warranty.

  • Lornetka Alpen Optics Teton 10x50
  • Lornetka Alpen Optics Teton 10x50
  • Lornetka Alpen Optics Teton 10x50
  • Lornetka Alpen Optics Teton 10x50
Manufacturer data


Alpen Optics
web site

Distribution / Sales:

web site

Magnification Lens diameter Angular field of view Prisms Eye relief Weight Price
10 50 102/1000(5.8o) BaK-4/roof 19 mm 850 g 2999 PLN
Results of the review
Real front lens diameter Left:   49.95+/- 0.05 mm
Right:  50+/- 0.05 mm
8 / 8.0 pkt
Real magnification 9.58+/- 0.2x 3/3.0
Transmission 88.7+/- 1% 16/25.0
Chromatic aberration Medium in the centre, very noticeable at the edge. 4.5/10.0
Astigmatism Very low. 7.5/10.0
Distortion The distance of the first curved line from the field centre compared to the field of vision radius: 64% +\- 4% 7/10.0
Coma Appears quite far from the field centre and at the very edge is medium at most. 7.4/10.0
Blurring at the edge of the FOV The blur appears in the distance of 92% +\- 3% from the field of view centre. 8/10.0
Darkening at the edge the FOV Slight. 4/5.0
Whiteness of the image Almost perfect. Very delicate cream tint. 4.2/5.0
Collimation Exemplary. 5/5.0
Internal reflections
Left: Right:
Alpen Optics Teton 10x50 - Internal reflections - Left Alpen Optics Teton 10x50 - Internal reflections - Right
Housing Solid, comfortable to hold and to look through. The inner tubes creak a bit under the pressure and the rubber next to objectives sticks out slightly. Objective caps are tethered on rubber straps to the tripod exit. They eyecups come with four click-stops. 6.3/8.0
Focusing Comfortable central screw. It moves smoothly and is well-damped (the full turn takes 450 degrees). A convenient, rubber-coated and ribbed ring on the right eyepiece. It works outstandingly but still it moves the outer lens. 4.7/5.0
Tripod The exit is very accessible. 3/3.0
Interpupilary distance from 58.5 to 74.7mm 5/6.0
Closest focusing distance 2.5 m. 2/2.0
Eyepieces FOV The apparent field of view of 55.3 deg (according to simple formula) and 51.5 deg (according to tangent formula). 7/20.0
Field of view Measured by us amounted to 5.77 +\- 0.03 degrees and, in the margin of error was according with the specifications. The field a tad too narrow for this equipment class. 5.5/8.0
Quality of the interior of the barrels Black. The beginning of the inner tubes is matt, then the surface is a bit shining. Bottom gray. Isolated specks of dust on the left prism. 3.9/5.0
Left: Right:
Alpen Optics Teton 10x50 - Vignetting - Left Alpen Optics Teton 10x50 - Vignetting - Right
Egg-shaped left pupil.
OL: 3.1%, OR: 0.0%
Prisms quality Good quality BaK-4. 8/8.0
Antireflection coatings Purple-red-yellow on objective lenses. Green-purple-yellow on eyepieces. Green on prisms. Low intensity. 5/5.0
Warranty [years] lifetime warranty 6/6.0
Final result
141 / 190 pkt
Econo result 0pkt.


  • relatively solid and light housing as for the 50 mm class,
  • good transmission,
  • low coma,
  • slight astigmatism,
  • well-corrected distortion,
  • field sharp almost to the very edge,
  • slight brightness loss at the edge of FOV,
  • very good whiteness reproduction,
  • good quality of prisms and coatings,
  • small minimal focusing distance,
  • slight inner flares,
  • very good guarantee conditions.

  • truncated left pupil,
  • a bit too high chromatic aberration,
  • for this price class the field of view should have been a bit larger.

The result of the Teton 10x50 speaks for itself – it is really brilliant. It’s enough to say it is only worse than a big, heavy, porro-prism Docter Nobilem’s result. After all, the Docters are a class of their own.

Still, there’s one but…it’s difficult not to have an impression that one part of these good results was reached by limiting the binoculars’ field of view to these 5.8 degrees. All the 10x50 binoculars, which scored similarly the Teton or higher, have fields of view at the level of 6.4-6.6 degrees. Such a field of view is expected from a well-designed, contemporary 10x50 instrument. The field of view narrower than 6 degrees means taking the easy way and for this the Teton could be criticized. On the other hand, though, the eyepieces’ apparent field of view larger than 55 degrees, as it is in the Teton’s case, doesn’t make observations uncomfortable. Only at the level of 45-50 degrees you might get annoyed with the impression of looking through the keyhole. Luckily, you get no such impression when it comes to the Teton.

In order to keep the balance we won’t write more about the advantages of the tested binoculars. Everybody who holds it and looks through it will be delighted with its relatively light weight, solid workmanship and good image quality, especially the field of view, which is sharp almost to the edge and corrects most of off-axis aberrations to boot. The coatings of this roof-prism binoculars also do a great job giving us a very nice whiteness reproduction and a relatively flat transmission curve, which reaches almost 90% at its peak – you can see it on the graph below.