Product Review: Pentax UD 9 x 21 Compact Binocular.

The Pentax UD 9 x 21 package.

A work commenced February 12 2021

 

 

Product: Ricoh Pentax UD 9 x 21

Country of Origin: China

Eye Relief: 9.9mm

Exit Pupil: 2.3mm

Field of View: 104m@1000m(6.0 angular degrees)

Close Focus: 3m advertised, 2.5m measured

ED Glass: No

Chassis construction: Plastic

Waterproof: No

Nitrogen Purging: No

Coatings: Fully broadband multicoated, no phase coating on prisms

Weight: 195g

Dimensions: H/W 8.7/10.8cm

Cost: £70.00 UK

Accessories: Case, carry strap, ocular lens caps, instruction sheet and warranty card

 

Over the last few years, I’ve come to really love and appreciate binoculars of all types – big ones, medium sized and tiny pocket glasses. In that time I’ve used several Pentax models, a little 9 x 28, a huge 20 x 60 and discovered the joys of the almost universally lauded Papilio II 6.5 x 21, noted for its exceptional close focus of about 0.5m. Pentax make good products, delivering quality optics and ergonomics at decent retail prices.

In August 2020, in the midst of a pandemic, Pentax launched their very economically priced UD series of pocket binoculars. Tiny and funky, their chassis come in a variety of colours; black, orange & grey, lime green and even pink. In addition, the UD series came with two magnification options 9 x 21 or 10 x 21. Intrigued by their appearance, I decided to order one up to see what was what. I went for the 9x model, as lower magnifications tend to have the least compromised optics. I chose the black chassis as I do not enjoy garish colours.

The product arrived double boxed. The binocular was accompanied by a nylon pouch together with a neck strap, ocular lens caps, a generic instruction manual and warranty card.

Ergonomics

The 9 x 21 Pentax UD is arguably the lightest binocular I have ever experienced. Weighing in at less than 200g, it made my 8 x 25 Opticron Aspheric LE and Leica Trinovid 10 x 25  seem heavy in comparison. The binocular chassis is constructed from ABS plastic and has no rubber armouring. Instead, it has a glossy finish that makes it a little bit of a challenge to grip properly, but once you get used to it, it doesn’t really present a problem.

The Pentax UD 9 x 21 has a glossy plastic chassis but no rubber armouring.

Fully deployed to my IPD, and with the eyecups extended upwards the binocular is as wide as it is tall. Here it is pictured side by side with the diminutive Leica 10 x 25 as a size comparison;

The Pentax UD 9x 21(left) compared with the Leica Trinovid 10x 25( right).

Despite its smaller physical size and mass compared to my other pocket glasses, the Pentax UD’s single hinge design means it can’t fold up as well as my Leica, with its dual hinge design, so storing it will require a little extra space.

The Pentax UD’s single hinge design means it can’t fold as neatly as the Leica (right).

The underside of the binocular has two small thumb rests that help you grip the instrument for a steady view:

Small thumb indents on the underside of the Pentax UD are designed for extra grip while glassing. Notice the single lug on the right barrel that attaches the carry strap, quite unlike anything I have seen before!

The eyecups are made of a soft plastic that can be twisted up for non-eyeglass wearers or left down for those who use glasses. However, the small eye relief of 9.9mm means that you won’t be able to see the entire field if using glasses. That wasn’t an issue for me though, but it’s definitely worth bearing in mind if you must wear eye glasses. However, the good news is that these eye cups click into place and hold their positions reasonably well.

The Pentax UD has fully multi-coated optics, which Pentax define as  “a multi-layer coating applied to all reflective lens surfaces.” However, those interested in looking at the 10x model might be somewhat disappointed as the above webpage states that it only has single layer coatings, which will definitely cut down on light transmission and contrast.

The ocular lenses are smaller than on more expensive pocket glasses I’ve showcased elsewhere on my website, and are more in keeping with those I encountered with the Kowa SV and Olympus WP II  8 x 25 models.

 

The ocular lenses are smaller than the 8x 25 Opticron, Leica and Zeiss 8/10 x 25 models.

The 21mm objectives are quite deeply recessed for a binocular of this size; certainly better than the Leica and Opticron 25 models I’ve used. The interior appears to be clean and dust-free and has decent baffling as well.

The green-tinted objective lenses on the Pentax UD appear to be well baffled and are fairly deeply recessed for a binocular of this size.

The focus wheel on the Pentax UD 9 x 21 is quite remarkable. On such a budget-priced model, I just wasn’t expecting such good quality. It is covered by a very grippy rubber substrate and moves smoothly with no backlash, either when rotating clockwise or anti-clockwise. It’s very intuitive and easy to use, owing to its large frame – a big plus on such a small binocular as this. Close focus was a very decent 2.5 metres and takes just over two full rotations to go from one end of its focus travel to the other. It also focuses a little beyond infinity, which is good for helping to clean up the edge of field performance of the glass.

The textured rubberised focus wheel is big and smooth to turn; a huge bonus on a small binocular!

The dioptre setting is very conventional and lies just under the right ocular lens. It is reasonably stiff but easy to use, and holds its position adequately in the field. As you can imagine, handling this binocular takes a bit of getting used to, as it is so small, but if your hands are not overly large, or if it’s being used by children and smaller adults, this shouldn’t present a problem. Remarkably, this tiny binocular can be mated to a tripod or monopod by unscrewing the cone shaped stalk at the head of the central bridge.

This featherweight binocular can be tripod mounted.

The UD series are not water or fog proof, so I would avoid using this model if you intend to explore the wet and the wild. That said, after I evaluated its optics, I can definitely see a niche for it. For more details, read on.

Optical Evaluation

On paper, the Pentax UD 9 x 21 doesn’t have much to write home about. The prisms are not phase coated(fully expected for a roof prism binocular in this price class), so light transmission and edge sharpness might have suffered somewhat as a consequence. After adjusting the right eye dioptre ring for my eye, my first impression was actually quite good! The image was brighter, sharper and more contrast-rich than I fully expected, but then again, Pentax know how to construct a decent binocular, and they sure as hell surprised me in the past!

Performing my iPhone bright light torch test, I was amazed to see that there was little in the way of internal reflections – excellent by almost anyone’s standards. It was clean and with little sign of diffused light like I had seen in other budget-priced instruments in this price class. It wasn’t perfect though. The intense torch beam showed up as a very strong diffraction spike; indeed the strongest spiking I’ve thus far encountered in my binocular education! But I had learned from many past experiences that this particular artefact would not be a fatal blow. Yes it did show up on bright outside lighting and while slightly annoying to see, you can quickly get used to it, especially if you avoid very intense night light sources or intend using the instrument only during daylight hours. In addition and for the record, no roof prism binocular is entirely free of this diffractive phenomenon; although more expensive models do manage to suppress it better.

Daylight observations of some tree trunks during bright winter sunshine served up an impressive image. The image was brighter than expected (remembering it has an exit pupil of just 2.3mm), contrast was good, colour tone seemed very natural, and the image has a nice big sweet spot, with only a little peripheral softness creeping in. How can this be achieved in such a low-priced binocular? The answer is by keeping the field of view on the narrow side. At 6.0 angular degrees (~ 5.9 measured), the image shows less field distortion at the edge of the field, allowing the sweet spot to seem impressively large. My notes on the Olympus 10 x 25 model showed that it served up a field of about 6.5 degrees in comparison, but the image had a noticeably smaller sweet spot and was quite badly distorted as one left the central part of the field, moving towards the field stops.

The Pentax UD 9 x 21 does show more veiling glare than I would have liked though. The glasser does have some control over this however, by observing under a roof or a forest canopy, or simply by stretching out one’s hand to shade the objectives better. That said, while it was no where near as good as the Opticron 8x 25 or superlative Leica 10 x 25, I have seen worse veiling glare in binoculars costing many times more than this little Pentax.

Colour correction is quite well controlled in the centre of the image, but does show some lateral fringing as a high contrast target(a telephone pole in this case) is moved off centre. In addition, there is some field curvature and pincushion distortion near the field stops.

Overall though, I was quite impressed with the optical performance of the Pentax UD 9 x 21, especially when you factor in its very modest price tag.

Brief Night Sky Assessment

Turning the Pentax UD 9 x 21 on the Hyades in Taurus, I was able to image the main stars in the bull’s horn. The stars were nice and tightly focused with most of the field being useful. There was definitely some softness and a bloating of the seeing discs  right at the edge though. The Pleaides looked good but a wee bit dim even for a pocket glass. Waiting up into the wee small hours of early February, with a break in the clouds, I finally had a chance to image the last quarter Moon fairly low in the sky. The Pentax delivered quite a decent image but you could clearly see the weak diffraction spike smeared across the field. This would definitely appear worse had I glassed a full or gibbous Moon.

Conclusions & Recommendations

The Pentax UD 9 x 21 is a fun little binocular. It offers very decent optical performance for a modest price. While it will never pique the attention of serious glassers who want to experience the very best views, there are many more people who just want something small, convenient and inexpensive, which will allow them to get close up to the action. It will therefore suit those who enjoy spectator sports, theatre goers, watching garden birds, trekking in the mountains, or campers who like checking out the local scenery. It’s small size, weight and inexpensive price tag, makes it ideal for kids and will provide a decent enough optical experience to sustain their curiosity until they cultivate the desire to buy a more serious instrument.  Its lack of waterproofing means you should take extra care and not use it in damp and rainy conditions but as long as you’re aware of these shortcomings you should be Ok to go!

 

Neil English is the author of seven books in amateur and professional astronomy. If you like his work why not consider supporting him by making a donation or buying one of his books? Thanks for reading!

 

 

De Fideli.

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