Product Review: Pentax SP 10 x 50 WP.

The Pentax SP 10 x 50 WP package.

A Work Commenced July 7 2021

 

Preamble

 

Product: Ricoh-Pentax SP 10 x 50 WP 

Country of Manufacture: China

Field of View: 87m@1000m( 5 angular degrees)

Eye Relief: 20mm

Close Focus: 5.5m

Exit Pupil: 5mm

Focuser: Central, lockable

Chassis Material: Aluminium with rubberised overcoat

Coatings: Fully broadband multi-coated throughout

Dioptre Range: +/- 4 dioptres

Nitrogen Purged: Yes

Waterproof: Yes (JIS Class 6)

ED Glass: No

Weight: 1060g

Dimensions: 18 x 18 cm

Retail Price: £170UK

Supplied with: Soft carry case, logoed carry strap, plastic objective and ocular covers, multi-language instruction sheet.

 

Pentax is a company long synonymous with good optical quality. Over the last few years, I’ve reviewed a few models manufactured by this company, ranging from the very small(6.5x 21) to the very large(20x 60). In particular, I’ve included an earlier incarnation of the  20 x 60 SP model in my own personal arsenal of binoculars, where it’s employed in deep sky observation and regular white light solar observing. So, I was excited to see how its smaller sibling, the 10x 50 SP WP, would shape up in field tests.

First Impressions

I purchased the binocular with my own money and it set me back £170, inclusive of delivery charges. The binocular arrived double boxed, including the instrument itself, packed inside its soft case, together with plastic end caps for both the ocular and objective lenses, a logoed padded next strap and instruction sheet containing information concerning the warranty. The plastic caps that protect the optics of the 10 x 50 SP looked identical to those that accompanied my 20 x 60, and together with the woefully inadequate soft case, represent the weakest links in the entire package. The caps are loosely fitting and invariably fall off  when the binocular is picked up. As for the case, it does very little to protect the binocular from serious knocks so should really be upgraded to either a padded soft case or better still, an aluminium hard case to protect your investment.

The Pentax 10x 50 SP WP is an extremely rugged and well made binocular, built for the great outdoors.

Ergonomics

Thankfully, my initial impressions of the binocular itself were far more favourable. When I unpacked it, I was immediately struck by its rugged build quality. The binocular weighs in at a hefty 1kg and is covered with a thick layer of synthetic rubber identical to that found on my 20 x 60 . Like its bigger brother, it has a lockable focuser; simply push the wheel forward and it disengages with the internal gearing, preventing the wheel from being moved. Although not an essential feature by any means, I can see where it would come in useful if one observes targets at a fixed distance from the user or when observing the night sky, where all the subjects are located more or less at infinity.

The central focus wheel is very easy to grip and is lockable simply by pushing it forward.

The twist up eyecups are very well made and very comfortable to use. There are three positions; fully down, intermediate and fully extended. Eye relief is a very generous 20mm. Usually, I observe with the eye cups fully extended but I actually found the view to be most comfortable and immersive at the intermediate position without wearing eye glasses.

The very solid twist up eye cups are comfortable to use and have three positions. Eye relief is generous allowing those who wear glasses to fully engage with the entire field.

The ‘WP’ part of its name, I assume, refers to ‘Water Proof,’ with a specified JIS class 6 rating. The instrument is purged with dry nitrogen gas to prevent internal fogging and is O-ring sealed. The dioptre ring is located under the right ocular lens and is negotiated by moving an easy to access lever which can be adjusted clockwise or anti-clockwise. It is reasonably stiff to the touch so should hold its position well. The underside of the 10x 50 SP WP has two large thumb indents for easier hand holding. I found that my thumbs naturally rested in them while holding the binocular up to my eyes.

The focus wheel is very stiff; a strict no-no for birding or any activity that requires rapid focus changes. But for stargazing or for stationary targets located in the distance, it works just fine.

You’ll find two large thumb rests on the underbelly of the binocular for more secure gripping.

Optics

The proof of the pudding, of course, lies in the eating, and this is where this well-made classic Porro prism binocular really shines. The SP series underwent an upgrade from the first generation models, with better multi-layer anti-reflection coatings being applied throughout the optical train. Allbinos tested this model out and measured a light transmission value of about 85%, which is very good indeed considering the modest price tag on this binocular, as well as the fact that some of the world’s best Porro prism binos achieve about 95% or so.

Not for the Birds

Inspecting the innards of the instrument in broad daylight showed it to be clean and dust free. Setting up my iphone torch to its highest setting in my back garden at dusk and placing it a comfortable distance away revealed a few minor internal reflections and no diffraction spikes or diffused areas; another good result indicating that all was well with the instrument in keeping bright light sources under control. Placing the beam just outside the field of view showed very little ghosting so this will be a good binocular to observe bright objects in the night sky such as the full Moon and stars located near it. It will also garner excellent views of cityscapes at night. Close focus was measured to be about 5.3 metres – a little better than advertised but nothing to write home about. The coatings on the ocular and objective lenses seem to be very evenly applied. In addition, the objective lenses are very deeply recessed which helps protect the optics from the vagaries of the British climate and also cuts down on stray light.

Very evenly applied multi-layer anti-reflection coatings applied to the objectives help transmit a decent amount of light through the optical train.

In broad daylight, the view through the Pentax 10x 50 SP WP is very impressive, with great contrast, good colour rendition and good control of glare. Depth of focus is not bad either. Colour correction is excellent, even off axis, where one can detect a small amount of lateral colour. Field curvature is very gentle but does show a fairly minimal amount of pincushion distortion near the field stops. Even though the field of view is fairly narrow at 5 angular degrees, it didn’t feel overly restrictive to my eyes. At 1kg weight and delivering a 10x optical boost, these are not binoculars that one could handhold for long but it’s certainly possible to scan the landscape and night sky for a few minutes before some fatigue sets in. These are however, perfect for use on a lightweight monopod or tripod for ultra stable viewing.

Further testing at dusk showed excellent control of internal reflections and clean, crisp images garnered from a bright sodium street lamp. Placing the lamp just outside the field of view showed up no significant off-axis flares. Placing the binocular on a light weight monopod and turning them on the night sky also served up excellent results. Centring the bright Summer luminary, Vega, in the binocular field and focusing in showed a pinpoint sharp image with no secondary spectrum and with no diffraction spikes. Better still, moving the star to the edge of the field induced only a little distortion and some lateral colour(purple fringing), indicating that the aspherical optical element built into the eyepieces of the Pentax SP binocular were doing their jobs well. And while the skies were far too bright to provide a more in-depth study, with strong Summer twilight upon us here in central Scotland,  I compared and contrasted the view through the Pentax 10 x 50 and my trusty Barr & Stroud Series 5 8 x 42 mounted on a second monopod. Turning my attention to the well placed Coathanger asterism in Vulpecula revealed a cleanly resolved view in both instruments, but with fainter stars showing up better in the Pentax, albeit in a smaller true field.

Conclusions & Recommendations

In recent years, thanks to great advances in technology, there has been a steady movement within the amateur community towards roof prism designs over older, Porro prism binoculars. But after spending a few weeks testing out this affordable model from Pentax, I was genuinely surprised and delighted by its optical performance. Indeed, you’d have to fork much more money for a roof prism binocular with the same specifications as this Pentax to get the same optical quality. The only real advantage of the roof prism incarnations at 10 x 50 are their lower mass(but not by much) and slightly smaller frames. Having sampled a few inexpensive and mid-priced 10 x 50 roof prism binoculars in the past, I can say hand on heart, that they did not deliver the light transmission values anywhere near those attained by this classic, affordable 10 x 50. Indeed, I would strongly recommend readers to look more closely at tried and trusted Porro prism designs in aperture classes of 50mm or above over the roof prism varieties, especially now that they come with full waterproofing.

Qui bono?

Amateur astronomers looking for quality deep sky views on dark, clear nights, and casual daytime viewers with permanently set-up tripods or monopods surveying targets set in the distance. Remember that five degrees is still plenty good enough for the vast majority of deep sky observing! These would work very well in holiday cottages set by a lake or overlooking a picturesque valley floor. And although they can be handheld for short excursions, they do benefit greatly from mounting.

Very highly recommended!

 

 

 

Dr Neil English has over 40 years experience studying the night sky with all sorts of telescopes, but in the last few years has devoted himself to seeking out bargains for savvy binocular enthusiasts. His highly lauded 650+ page magnum opus, Chronicling the Golden Age of Astronomy, summarises four centuries of telescopic observing, from Thomas Harriot to Patrick Moore.

 

 

De Fideli.

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