Pentax SP 10x50 WP
All pairs of binoculars from that series have prisms made of BaK-4 glass and all air-to-glass surfaces are covered by antireflection multilayer coatings.
The body of the binoculars, nitrogen-filled, is made of aluminum and covered by rubber armour. The internal eyepiece bridge means the SP WP series belongs to a very limited group of Porro binoculars with central focusing which are completely submersible (up to 1 meter, JIS Class 6).
Buyers get both caps, a strap, and a case in the box. The binoculars come with 30-year warranty period of the producer.
| Magnification | Lens diameter | Angular field of view | Prisms | Eye relief | Weight | Price |
|---|---|---|---|---|---|---|
| 10 | 50 | 87/1000(5o) | BaK-4/Porro | 20 mm | 1060 g | 799 PLN |
| Real front lens diameter |
Left: 50.03+/-
0.05 mm Right: 50.02+/- 0.05 mm |
8 / 8.0 pkt | ||||
|---|---|---|---|---|---|---|
| Real magnification | 9.77+/- 0.1x | 3/3.0 | ||||
| Transmission | 84.2+/- 1% | 12/25.0 | ||||
| Chromatic aberration | Slight in the centre, a bit higher than medium on the edge. | 6.5/10.0 | ||||
| Astigmatism | On a medium level. | 6/10.0 | ||||
| Distortion | Distance between the first curved line and the field centre compared to the field of view radius: 89% +\- 2% | 10/10.0 | ||||
| Coma | Appears in a distance of 60% of the field of view radius and is a bit higher than medium on the very edge. | 5.1/10.0 | ||||
| Blurring at the edge of the FOV | Blur occurs in a distance of 69% ± 4% from the field of view centre. | 3/10.0 | ||||
| Darkening at the edge the FOV | Negligible. | 4.5/5.0 | ||||
| Whiteness of the image | A distinct pit in the middle of the range but the difference in transmission for red and blue light are within 5% so colour rendering is good. | 4/5.0 | ||||
| Collimation | Perfect. | 5/5.0 | ||||
| Internal reflections |
|
3.7/5.0 | ||||
| Housing | Classic Porro design with dark rubber armour which sticks to your hands quite well. Thumb recesses ensure a firmer grip. Rubber covering one tube is a bit loose and is a bit too carelessly glued together near the objective lenses. Produced in China. Rubberized, three-position twist-up eyecups. | 6.7/8.0 | ||||
| Focusing | Comfortable, ribbed central wheel which is well damped and can be locked. Its full range Leeds a turn through An angle of 540 degrees. A comfortable ring with ribs on the right eyepiece for dioptre adjustment moves the outer element. The bridge doesn’t bend under pressure but moves sideways a bit. | 4/5.0 | ||||
| Tripod | Very comfortable access. | 3/3.0 | ||||
| Interpupilary distance | from 57 to 73.3mm | 4/6.0 | ||||
| Closest focusing distance | 5.20 meters. | 1/2.0 | ||||
| Eyepieces FOV | Apparent field of view of 48.6 deg (according to simple formula) and 46.0 deg (according to tangent formula). | 3/20.0 | ||||
| Field of view | Measured by us amounted to 4.97 +\- 0.04 degrees and it was in accordance with specifications. A narrow field for this class of equipment. | 5/8.0 | ||||
| Quality of the interior of the barrels | Dark and matt tubes; the bottom quite dark as well. Black glue. Quite clean inside. | 4.7/5.0 | ||||
| Vignetting |
|
5.5/8.0 | ||||
| Prisms quality | Good quality BaK-4. | 8/8.0 | ||||
| Antireflection coatings | Greenish everywhere. Medium intensity. | 4.5/5.0 | ||||
| Warranty [years] | 25 | 5/6.0 | ||||
| Final result | 65.9% | 125.2 / 190 pkt | ||||
| Econo result | 0pkt. |
Summary
Pros:
- solid-looking and completely waterproof casing,
- good colour rendering,
- BaK-4 glass prisms,
- negligible distortion,
- imperceptible brightness loss on the edge of the field of view,
- excellent blackening and cleanliness inside tubes,
- sensible antireflection coatings,
- 30-year warranty period.
Cons:
- narrow field of view with mediocre sharpness on edges,
- a bit truncated exit pupils.
 |
Currently, there’s no Minolta anymore and the Action EX series can be bought at a different price point, around the 150 EURO, even though the optical properties got worse and quality control decreased (e.g. not all air-to-glass surfaces are coated).
The price of the Pentax SP 10x50 WP compared to the price of its predecessor has been lowered as well but that drop is not as significant as in the case of the Nikon. Did the producers economize on optics? The number of coatings wasn’t reduced for sure because all air-to-glass surfaces are covered and our transmission graph confirms that.
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It seems the field of view, amounting to just 5 degrees, might be the biggest flaw of the tested instrument. With such a size the field should have been corrected in a perfect way but it isn’t. We are especially concerned by weak resolution on the edge – it is a serious problem.
The build quality and lack of evident economizing are the biggest assets of the SP 10x50 WP for a change. For merely 200 EURO you get a very solid Porro device which is completely waterproof even though it features a central focusing mechanism - a truly unique feature, there are almost no such binoculars available on the market. I would recommend the Pentax to those who care more about the usefulness of the instrument than its optical performance. Without spending a lot of money you get a pair of binoculars which will serve you well even in the harshest weather conditions.
