Binoculars review

Pentax SP 10x50 WP

Pentax SP 10x50 WP
30 August 2017 
The Porro SP WP series produced by Pentax was launched on the market in 2015 superseding PCF WP devices. In practice it meant the barrel was changed a bit and 7x50 and 16x60 models disappeared from the line-up, leaving instruments with the following parameters: 8x40, 10x50, 12x50 and 20x60.

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.

  • Lornetka Pentax SP 10x50 WP
  • Lornetka Pentax SP 10x50 WP
  • Lornetka Pentax SP 10x50 WP
  • Lornetka Pentax SP 10x50 WP
Manufacturer data


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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
Results of the review
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% 11/15.0
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
Left: Right:
Pentax SP 10x50 WP - Internal reflections - Left Pentax SP 10x50 WP - Internal reflections - Right
A bit lighter areas around exit pupils.
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 degrees. 4/10.0
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
Left: Right:
Pentax SP 10x50 WP - Vignetting - Left Pentax SP 10x50 WP - Vignetting - Right
OL: 2.31%, OR: 1.47%
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
124.2 / 170 pkt
Econo result 0pkt.


  • 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.

  • narrow field of view with mediocre sharpness on edges,
  • a bit truncated exit pupils.

More than a dozen years have passed since we did our big 10x50 class binoculars test with the participation of the Pentax PCF 10X50 WP. The market conditions have changed as well. Binoculars from manufacturers of photographic equipment such as the Pentax PCF 10x50 WP exactly, the Minolta Activa 10x50 WP.FP or the Nikon Action EX 10x50 used to lead the market when it came to mid-level Porro models. All of them came with a price of over 200 EURO and were really worth it.

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.

It is characteristic for cheaper multi-coatings. Their distinct, greenish hue means that light colour is reflected the most and our graph shows it as well – around 500-550 nanometers you can notice a significant loss. Red light transmission reaches a high level of over 90% and we got 88% for the blue part of the spectrum. Taking into account the price of the instrument such results seem to be quite sensible. The images provided by the Pentax are bright, without any noticeable colouring. Currently such a result is rare indeed among budget class Porro binoculars.

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.