Product Review: Pentax Papilio II 6.5 x 21.

The little butterfly binocular; Pentax Papilio II 6.5 x 21.

June 19 2020

 

Binocular: Pentax Papilio II 6.5 x 21mm

Cost: £109.00 delivered

Optics: Reverse Porro /patented converging objectives for ultra-close focus

Coatings: Fully Multi-coated

Exit Pupil: 3.23mm

Field of View: 7.5 degrees (132m @1000m/ 323ft@1000yards)

Focus Range: 18 inches to infinity

Eye Relief: 15mm

Weight: 290g

Tripod Mountable: Yes

Dimensions: 11.0 x 11.4cm(W/H)

Nitrogen Purging: No

Waterproof: No

Accessories: High quality neck strap, rain guard, carry case, instruction manual and warranty card.

Life is full of surprises; some good and some bad. I’m happy to report a surprise of the pleasant variety in this review, featuring the Pentax Papilio II 6.5 x 21 binocular. Though it’s been on the market for several years now, it fell below my radar partly because I became rather fixated with high quality roof prism binoculars and never considered the old classic designs using porro prisms.

Porro prism binoculars are easier to make well in comparison to their roof prism counterparts. They are also considerably less expensive compared with roof prism models of similar quality. To some, their fall from grace in recent years was not due to their inferior optical quality, but more to their larger size and ‘outdated ergonomics.’ That said, they still have a loyal following among those who appreciate fine optics.

In my recent survey of the pocket binocular market, being somewhat dismayed by the lack of credible user reviews,  I went on a shopping spree to test out literally dozens of models – all from the roof prism variety – learning that in general, you get what you pay for. But there is always something new to learn and over the last few weeks I’ve been putting this tiny little binocular through its paces.

And it’s been a revelation!

The name ‘Papilio’ derives from the Latin for butterfly. Pentax were the first company to design these reverse porro binoculars featuring a patented converging objective system that allows these instruments to focus on objects as close as 18 inches – way closer than any roof prism binocular can do. The design was an instant success and thousands of nature enthusiasts snapped them up to provide wonderful stereo-microscope-like views of flowers, leaves, insects  etc. The first generation models had a few shortcomings though, as the literature is awash with reports that the anti-reflection coatings were not up to scratch. Experienced glassers reported bright reflections off the eyepiece field lenses and annoying internal reflections, cutting down on contrast and increasing glare in strongly back-lit scenes. Some resourceful users reported ways of reducing some of these annoying shortcomings however, such as using a broad-rimmed hat to cut out peripheral glare for example, or using them in deeply shaded areas where the contrast-robbing deficiencies in the coatings were less obvious etc. Others just accepted their shortcomings and simply enjoyed them as specialised, close-focus devices to study the complexities of the creation.

But then Pentax brought out a second generation Papilio featuring much improved anti-reflection coatings on all glass surfaces. Called the Papilio II, they are offered in two models; a 6.5 x 21 and an 8.5 x 21. Being the proud owner of a superlative 8 x 20 pocket glass by Leica, I was more interested in the lower power 6.5x model, as it seemed to be the least compromised of the two and would also offer me a larger exit pupil, which is both easier to operate in general use and would prove superior to the 8.5x model in low light situations at dusk or dawn, or on heavily overcast winter days.

First Impressions

The Pentax Papilio II package.

The binocular arrived double-boxed and contained the binocular, a nice faux leather case, a high quality neck strap, a rain guard covering the ocular lenses, operating instructions and a warranty card. A quick examination of the instrument revealed that all was well; the eyepieces could be extended with a click, the focuser worked smoothly, as did the right eye dioptre ring, and the objective lenses housed inside an optically flat glass window were spotless.

To ocular end of the Pentax Papilio II 6.5 x 21 binocular.

The padded neck strap was a breeze to attach. because it has built-in clips. All one need do is push them through the two holes on the side of the instrument where they are held firmly in place. What a delightful change from threading the strap through tiny little lugs!

The body seems to be made of ABS plastic and covered in a thin layer of texturised rubber which affords excellent grip while manhandling. The double hinges are quite stiff and once the optimal IPD is set, they stay in place. The underside of the binocular has neat little thumb indentations which makes holding it a wee bit easier.

The under side of the Papilio II has thumb indentations for easy handling in the field.

The dioptre ring also served up a pleasant surprise. Instead of rotating smoothly and silently either clockwise or counter-clockwise, this dioptre has click stops that you can hear as you rotate it. At first I was a little concerned that it may not offer the precision of a smoothly rotating right eye dioptre ring, but my wife and I were able to adjust it to accommodate our different settings easily and accurately. Just like some premium roof prism binoculars which have a built-in click stop dioptre, the low cost Papilio II offers the same security against accidental movement. A very clever engineering solution!

The eyecups are plastic and covered in soft rubber. They offer three positions; fully down(for eye glass wearers) or two clicked up positions, affording a maximum eye relief of 15mm. To my relief, I found that they hold their positions very rigidly and work well in field use.

I was also very impressed with the large textured central focus wheel, which moves quickly and very smoothly with no backlash. It has a very large focus travel though, requiring 3 full rotations going from its closest focus at 18 inches right out to infinity. Good focusers are an essential feature of a binocular and I felt Pentax went that extra mile to make sure it worked well.

The objectives are housed behind an optically flat window which also has good anti-reflection coatings applied to it in order to ensure high light transmission and minimise glare. At first I thought the window would be a negative addition, as it might have introduced more unwanted reflections than I bargained for, but as you shall see shortly, I need not have worried!

The optically flat glass window protecting the moving objectives is anti-reflection coated, helping to keep contrast high in the final image.

A straight through look shows the objectives behind the glass window. Note the low reflections off the window itself.

Another really neat feature of this Pentax Papilio II binocular is the in-built thread on its underside that allows it to be mated to a tripod for more exacting work. This is a rare feature on instruments this size but I can think of many situations – both in the great outdoors and in an indoor studio – where it could prove very beneficial. What a super nice touch!

Note the built in tripod-friendly thread on the underside of the binocular.

A quick look through the instrument instantly impressed. The image of a tree trunk some 50 yards distant was bright, tack sharp and very high in contrast. I was also impressed by its wide field of view – 7.5 angular degrees ain’t too shabby! But I was literally blown away when I focused in on a flower bed of Johnson’s Blue Geraniums sat just outside my front door. Wow! The view was quite simply astounding! Placing myself just 2 feet away, the sharpness and colour fidelity of the image was excellent and the level of detail seen within the individual flowers was mesmerising!

Stray Light & Glare Test

But I took heir of myself and proceeded to test the binocular in my usual ways. So first I set up a flashlight test in my living room, by setting my iphone torch setting to its highest(read brightest) level, and standing a few metres back, I aimed the binocular into the intensely bright light beam. Wow! The result was excellent! Compared to a few high quality control instruments (all roofs), the Papilio II showed a few very minor, green coloured internal reflections with no diffraction spikes and no diffused light. Comparing it to my Zeiss Terra 8 x 25 pocket glass, the reflections in the Papilio were only slightly stronger but without any diffraction spikes. Indeed, diffraction spikes are almost a universal feature of roof prism binoculars, however well built, but porro prism instruments seem to be devoid of these. Even the venerable Leica Trinovid BCA 8 x 20 showed an obvious diffraction spike in the same test though its internal reflections were better suppressed than in the Papilio II.

The Pentax Papilio II 6.5 x 21 has excellent control of stray light, as compared with a top-performing Zeiss pocket glass costing nearly three times more!

Later in the evening, when the sodium street light came on, I once again compared the Papilio II and the Zeiss pocket glass. As expected, the Papilio II delivered excellent results; very subdued reflections and no diffraction spikes. As a glasser who cannot stand excess glare and internal reflections, I was thoroughly delighted with the results I obtained from this low-cost binocular.

So far so very good!

Collimation Test

Collimation checking and right eye dioptre adjustment are best done on a tripod.

By affixing the Papilio II to a tripod, it’s easy to check the collimation of any binocular. Aiming at the hilltops a couple of miles distant, I checked the field of view both horizontally and vertically in both barrels. The results showed very slight horziontal misalignment( as evidenced by a slight asymmetry in the edge of field views) but perfect vertical alignment. I deemed the result quite satisfactory.

A tripod-mounted binocular is also a good way to tweak the right eye dioptre by focusing on the writing on a council notice affixed to a lamp pole some 40 yards in the distance. The dioptre ring clicks as it moves clockwise or anticlockwise making it real easy to get the optimal sharpness in the right barrel when it is locked rigidly in place.

Optical Tests

I conducted my optical tests under a variety of conditions, ranging from bright afternoon daylight in the open air, shaded areas underneath the canopy of trees while walking around in a copse, performance at dusk and finally looking at some bright stars in a twilit June sky around local midnight.

Comparing the performance to my Zeiss Terra 8 x 25 ED, I was very impressed with the optical performance of the Papilio II 6.5 x 21. To my eye, the images of textured tree trunks looked equally sharp in both binoculars, with the Papilio displaying the wider field of view at a smaller image scale. Contrast was excellent in both instruments, which both sport very large sweet spots, and only showing slight softening at the extreme edge of the field. The Papilio features aspherical ocular lenses which keeps off-axis aberrations at bay. In this respect, the Papilio II produced less field curvature(as evidenced by aiming at a telephone pole a few tens of yards distant and moving the pole to the edge of the field) than the Zeiss. Indeed, I pulled out my wife’s Opticron Aspheric LE 8 x 25 which also sports aspherical ocular lenses and displays superior edge sharpness to the Zeiss Terra, as reported in a previous blog. Well, the Papilio II proved fully the equal of the Opticron pocket glass on the same target!

The Pentax Papilio II 6.5 x 21( left) and the Opticron Aspheric LE 8x 25 (right).

Under the brightest daylight conditions it is easy to detect reflections off one or more of the ocular lenses as this manifests as a subtle circular glare disc covering much of the field. Alas, these annoying reflections are all too common on a lot of instruments that skimp on their application of anti-reflection coatings. I was very pleased to see that the Papilio II also passed this test with flying colours – that is, it was not present. Chromatic aberration was pretty much non-existent even when pointed at a tough target like a television aerial against a bright overcast sky.

Comparing the Papilio II to my Zeiss 8 x 25 roof prism binocular under the shade of  conifer trees near my home, I found both binoculars to yield up equally bright and sharp images of ground vegetation just a few metres away. When I did the same tests with the Opticron, I felt the Papilio served up slightly brighter images although the sharpness was judged to be more or less the same.

Going out at dusk around 10.15 pm, I compared the brightness of the images of tree branches about 50 yards distant served up by the Pentax Papilio II, the Zeiss Terra ED 8 x 25 and my Leica Trinovid 8 x 20. The Papilio II and the Zeiss pocket glass threw up images that were about equally bright, with the nod going to the Zeiss ( but only just!). Comparing the Trinovid 8 x 20 to the Papilio II in similar tests showed that the images were noticeably brighter in the latter instrument.

The Leica Trinovid BCA 8 x 20 (left) and the Pentax Papilio 6.5 x 21(right).

All in all, these were excellent results showing that the light transmission efficiency of the Papilio was very good indeed based on Zeiss’ published data on the Terra glass, which has 88 per cent transmission. The dimmer images served up by the Trinovid was easily explained in terms of its smaller exit pupil (2.50mm compared with 3.23mm).

My final optical tests were conducted under a twilit night sky ’round about local midnight. I aimed the binocular at the bright summer star, Vega, and compared the views in both the Zeiss and the Papilio II. Both instruments focused Vega down to a crisp, white pinpoint that held its sharpness across nearly all of the field. Moving the instruments horizontally showed better off axis performance than those exhibited by moving the star up and down, to the top and bottom of the field, respectively. The only difference I could detect was the darker sky hinterland in the 8 x 25 Zeiss pocket glass, perhaps owing to its higher magnification.  But even so, the differences weren’t huge.

These tests convinced me that the Pentax Papilio II 6.5 x 21 has excellent optics, especially for its very modest price tag. Its simpler design to roof prism binoculars means it has less optical components overall, and the combination of aspherical ocular lenses, high quality Bak 4 prisms and fully multi-coated optics all contribute to this high optical field performance.

Further Notes from the Field

Using the reverse porro prism designed Papilio II takes a bit of getting used to. At first, its strange body shape reminded me of a scene from a Star Wars Movie when Luke Skywalker used weird looking binoculars to monitor the movements of marauding Sandmen lol. That said, it’s quite easy to hold steady and most anyone can use it, including kids.

Though it is just as lightweight and portable as a pocket binocular, it doesn’t fold nearly so compactly as a dual hinged pocket glass like the Zeiss Terra 8 x 25, as shown below:

Though it weighs just as little as a light weight pocket binocular like the Zeiss Terra 8 x 25(bottom), it cannot fold up quite so small but will fit in a large coat pocket or a ruck sack.

The Pentax Papilio II 6.5 x 21 can be used as a decent birding binocular, with its quality optics and fairly large and very well corrected field of view.  Its super-fast focus wheel also helps in this regard. One drawback of its lower magnifying power compared with more conventional glasses (which almost invariably use powers of 7x to 10x) is reduced range. Sometimes you just need 8x or 10x to bring the subject sufficiently close in order to get a good view of it. And 6.5x may not be the best choice for a twitcher, where the subject is heavily camouflaged, small or located at a lengthy distance from the user. For close-range work (read within a couple of hundred yards) it should work well though. Its small aperture will also limit its use to bright daylight conditions most of the time, and thus will be less suitable for work when lighting is compromised, such as at dawn or dusk, in which a larger aperture glass would serve you better.

The instrument is absolutely head and shoulders above any other instrument on the market if your speciality is close-up work, like studying insects, flowers, rocks and minerals. It will also prove indispensable to artists who paint still life scenes indoors, where the instrument can be permanently mounted on a clamp or tripod, where the subject can be examined in exquisite detail under optimal lighting conditions. It also serves as a very effective stereo microscope, affording very comfortable and immersive views of a wide variety of subjects.

I have noted that for such close-up work, the Papilio II 6.5 x 21 seems to provide greater than advertised magnification. When viewing flowers at 18 inches, for example, the power seems closer to 7.5x or 8x and not the advertised 6.5x. This is probably true of the 8.5 x 21 instrument as well, where a power of 10x or more might be expected during these close-range observations.

The binocular is not weather or water proof, which might be a negating factor in choosing it for general purpose viewing or bird watching. In cold weather, it will fog up when brought from the outside to a warm indoor room. I would not recommend using the instrument in rainy or showery conditions. But there are ways to protect it from fogging up internally. For example, by placing the instrument back in its case with the rain guard on prior to bringing it indoors is a good move, as would storing the instrument with an effective desiccant, like silica gel, will help keep moisture at bay and prolong its shelf life, especially if you live in humid climes.

The instrument is not really recommended for astronomical use, though it will serve up very nice news of illuminated cityscapes owing to its good control of stray light within the optical train. That said, it ought to serve up nice images of the Moon and bring some of the brighter deep sky objects into view from a dark, country sky.

I have noted that the optically flat glass window protecting the objective lenses is a magnet for attracting pollen. Not a big deal in the scheme of things, but something to bear in mind. You’ll need a soft lens brush to keep the window clean. I tend to give it a brush down after any prolonged spell(more than 30 minutes or so) outdoors.

The glass window protecting the objective lenses attracts a lot of pollen so will require regular brush down after prolonged field use.

Another niggle reported by some users of the Pentax Papilio II binoculars is that the supplied carry case is too small to comfortably house the instrument when the neck strap is attached. And while removing the strap is one solution, it might not be to the liking of some individuals who wish to use it in the spur of the moment. I have found a solution of sorts, by placing the binocular in the case while feeding the two ends of the strap out from both ends of the case cover. The strong velcro seal is plenty strong enough to hold the binocular in place inside the case and the straps can be used to carry it about!

The neck strap can also double up as carry strap for the case & binocular.

As always, I store the binocular inside its case with a sachet of silica gel and store it in a cool( 60 F), dry and well ventilated pantry to protect against fungal infestation.

Conclusions: The Pentax Papilio II 6.5 x 21 was a very pleasant surprise. For its modest cost of just over £100, you get very decent classic porro prism optics with unbeatable close-focus capability. I think every binocular enthusiast should own one! Far from being a one-trick-pony, it will serve as a very versatile instrument for casual viewing, nature study and bird watching. Just understand that it can’t be used in rainy conditions and needs protection from internal moisture build up in humid climates requiring extra care when storing for long-lived use.

Highly Recommended!

Neil English is the author of seven books in amateur and professional astronomy. If you like his work, please consider purchasing one of his books. Thanks for reading!

De Fideli.

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