Thoughts on the Pentax Papilio II 8.5 x 21 Binocular.

The Pentax Papilio II 8.5 x 21.

A work began July 9 2020



Binocular: Pentax Papilio II 8.5 x 21mm

Cost: £85.99 delivered

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

Coatings: Fully Multi-coated

Exit Pupil: 2.47mm

Field of View: 6.0 degrees (105m @1000m/ 315ft@1000yards)

Focus Range: 18 inches to infinity

Eye Relief: 15mm

Weight: 295g

Tripod Mountable: Yes

Dimensions: 11.6 x 11.0cm(L/H)

Nitrogen Purging: No

Waterproof: No

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


In a previous review, I expressed my astonishment at the quality of the views served up by the Pentax Papilio II 6.5 x 21. Not only did it deliver extraordinary, ultra-close up views of the creation quite unreachable by any conventional binocular, but it also impressed when functioning in its normal way, when imaging objects at a distance. The little Papilio also has a higher power sibling, delivering a power of 8.5x with the same size objective(21mm). In this blog I would like to offer my opinions on how it performs on its own terms but also in comparison to the 6.5x model as well as a very high quality control instrument; the Leica Trinovid BCA 8 x 20, which I reviewed some time ago.

Now, you’ll appreciate that these kinds of tests are hardly ever done by other glassing enthusiasts, partly because it will almost always be assumed that a binocular costing £85 could never compete with a glass retailing for nearly £400. Furthermore, when you are in possession of one of the most elegantly designed pocket glasses in the world, you don’t want to be told that something a lot cheaper could even compete with it. It’s only human nature to take pride in an expensive glass from a world-class optics firm, but this kind of pride, when taken too far, can blind you to greater and more important truths.

Having said that, these two compact binoculars are very different beasts; the little Leica is a roof prism binocular and is optically more complex than the Pentax Papilio II 8.5 x 21, which has a much simpler, reverse porro prism design. And because the latter is simpler, it’s easier to make well, so the rather enormous price differential between the two instruments doesn’t really tell the whole story, as I was to find out.

Let’s first take a few moments to compare the specifications on both the Leica and the 8.5x Papilio II. The Pentax delivers a power of 8.5x with a 21mm aperture objective giving an exit pupil of 2.47mm. The Leica delivers a slightly lower power of 8x with an objective aperture of 20mm and so yields a very similar exit pupil size of 2.50mm. The Leica weighs in at 235g whilst the Papilio tips the scales at 295g, So both can be carried pretty much anywhere with ease, based on weight considerations alone. There is a considerable size difference though, as you can clearly see from the photo below; the Leica is a true pocket-sized glass, capable of being folded up in such a way that it fits easily in the palm of your hand. The Papilio, while still very compact, cannot achieve this level of compactness. So, if storage size is set at an absolute premium, the Leica would be the obvious choice. That said, are there really that many circumstances where the storage size difference really matters that much? I would argue that in most realistic situations, this difference isn’t that important.

Stray light and Internal Reflection Tests

Managing stray light inside a binocular is an important parameter in delivering contrast in a binocular image. Thankfully this is easily assessed by aiming the glass at an intense source of bright light like your iphone torch set to its maximum brightness setting and examining the images garnered through the test instrument. As I explained in my review of the lower power 6.5x Papilio II, I was quite impressed with the results I got. There were some internal reflections but they were quite feeble in comparison to many other models I have tested. The Papilio II 8.5x was not as good in comparison. It showed noticeably brighter internal reflections than the 6.5x instrument but the image was still quite clean, with very little diffused light around the light beam and no diffraction spikes. In comparison, the Leica Trinovid 8 x 20 was much better. The internal reflections were much more aggressively suppressed(but still there!) and the image was cleaner and had practically zero diffused light around the light beam. It did however, show a pronounced diffraction spike in comparison to both Papilio binoculars.

Predictably, these internal reflections were also more apparent in the 8.5x Papilio II than in its 6.5x counterpart when pointed at a bright sodium street lamp. That said, I didn’t consider this a serious flaw, as I have tested many binoculars showing considerably worse performance that still delivered good daytime views.I would however expect that the 8.5x model might show up more in the way of internal reflections when pointed at bright astronomical sources like the full Moon.

The difference in performance between the 6.5x and 8.5x in regard to controlling stray light is likely attributed to less rigorous quality control in the manufacture of these binoculars. This is probably par for the course for these low cost instruments. It is wholly realistic to expect significant inter-individual performance differences with these mass produced binos, where one sample delivers excellent stray light suppression and another delivering not so good performance in the same tests.

Veiling Glare Tests

As I explained in much more detail in a previous blog, veiling glare is a phenomenon that manifests itself in all binoculars, no matter how well designed they are. It can be seen when glassing in the open air on an overcast day while imaging a deeply shaded target, such as the edge of a wooded area. The most likely cause of this is due to reflections off the bottom lens spacers between the objective lenses, which manifests as a ‘cloudiness’ that covers much of the field reducing contrast in the binocular image. I tested the two Papilio binoculars as well as the Leica Trinovid in this regard and the results were interesting but not entirely surprising!

Both Papilios showed considerably less veiling glare compared with the little Leica. Imaging a shaded copse under a bright overcast July sky showed that the little butterfly binoculars were controlling this rather annoying glare much better than the far more expensive Leica glass. The reason for this is probably due to the fact that the Leica objectives are almost completely exposed to the overhead light as they are not recessed as deeply as the Papilios, which house their objective lenses well behind an optically flat glass window and so are much better protected from the ambient light. I found the differences between them to be quite striking, so much so that it could make all the difference between seeing something clearly and not seeing it at all! Thankfully, veiling glare is easy to remove from the image by simply shading the objectives with your hand, but it was interesting to see how differences in design can manifest quite striking differences in performance in this regard.

Daylight Optical Performance 

After adjusting the click-stop dioptre ring under the right eye ocular lens, I began to test the Papilio II 8.5 x 21 on a variety of targets and compared it to the Leica Trinovid BCA 8 x 20. I found this higher power Papilio to a very good optically. The images were clean and sharp and high in contrast. Indeed, they were very similar to those served up by the Leica glass. Looking critically at some tree trunks illuminated by bright sunlight showed that both glasses served up the same amount of fine detail. Contrast was a shade better in the Leica glass. Edge of field correction was also very similar in both glasses too, with both showing very mild pincushion distortion near the field stop. I did however detect slightly more lateral colour in the Papilio II than in the Leica but I felt that it did not detract much from the quality of the image.

However, I found some significant differences in depth of focus when comparing both binoculars though. The Pentax Papilio had a noticeably shallower field depth compared with the Leica, which surprised me, and, as a result, renders it that little bit harder to focus accurately. I found myself slightly under or over shooting the focus wheel on the Papilio II before I got the precise focus required while glassing a variety of targets in the open air. This might have been expected knowing that depth of field seems to decrease with increasing binocular magnification, although in this case the difference was small (8.5x for the Papilio and 8.0x for the Leica), so the discrepancies I noted might well be due attributed to differences in design of the binoculars than anything else.

I didn’t think a difference of 0.5x increase on the Papilio II would give a noticeable increase in image scale, but I was wrong about that. This represents a 6 per cent increase in image scale and that’s large enough to notice! What this means is that the 8.5x Papilio II will give you slightly more reach with small or distant targets while glassing under good seeing conditions.

I must also report that my eyes were experiencing more in the way of blackouts in the Papilio II 8.5 x 21 compared with the Leica Trinovid though. I attribute this to my lack of practice centring my eyeball properly inside the large eyepiece cups on the Papilio. In comparison, the smaller eyecups on the Leica make centring that little bit easier to accomplish since I have had far more practice with the latter than the former glass. But I would expect these blackouts to reduce in frequency with more practice. The reader will note however that the eye relief is slightly more generous in the Papilio than on the Leica(15mm in comparison to 14mm, respectively). And since the Papilio II 8.5 x 21 has a smaller field of view than the Leica (6.0 and 6.5 degrees, respectively), it will be easier to image the entire field with it compared with the Leica glass.

Of course, one of the key ways in which the Papilio II 8.5 x 21 trumps the Leica is in close focus. The former, which has a patented converging objective lens design, enables its users to obtain stunning ultra-close views of flowers, insects, rocks, gemstones  etc, which simply cannot be achieved with the cute little Leica glass. Indeed, the close focus of the Leica Trinovid (~3 metres) is rather lacklustre in comparison with other pocket glasses I have used in the past, so if butterfly or insect viewing is your thing, the Papilio IIs will serve you much better.

Low Light Performance

Though such small aperture binoculars have limited use in low light situations, such as those encountered during dusk or dawn, I wanted to establish whether there was much of a difference, if any, between both glasses when imaging the same target under twilight conditions that we encounter here in central Scotland during the middle months of the year.  Venturing out about 10pm in the second week of July, I compared the brightness of the images served up by both the Pentax Papilio II 8.5 x 21 and the Leica Trinovid 8 x 20, by examining tree branches situated about 40 yards distant. My results were very encouraging; both glasses seemed to be delivering equally bright images under these conditions, with the nod going to the Leica. I expected this result owing to the similar exit pupil size of both instruments as well as the application of good anti-reflection coatings to the optical components. This indicated that the Papilio IIs have very good light transmission, which is an important commodity in any binocular.

Some Astronomical Tests

With all the churches shut down, I was able to carry out some tests on both the Pentax Papilio II 8.5 x 21 and the Leica Trinovid 8 x 20 in the wee small hours of Sunday July 12. Starting about 2.20am local time, I ventured out to witness a bright, last quarter Moon rising in the east, and just a few degrees above it and slightly off to the west, fiery red Mars.The sky was not fully dark but still bathed in twilight. Comparing the views in both the Papilio and the Leica, I noticed some very weak internal reflections in the Papilio which were not present in the Leica. Moving the Moon laterally from the centre to the edge, I observed that the Papilio showed some significant darkening  towards the edges but thanks to its aspherical eyepieces, the image of the Moon stayed sharp. In comparison, the Leica showed much less drop off in illumination at the edge of its field.

But things were noticeably different when I repeated the same test in the vertical direction. Again, placing the Moon in the centre of the field, and then gradually moving it to either the top or bottom field stops in both binoculars, the little Leica proved to be the clear winner. The Moon was much more strongly de-focused in the Papilio than in the Leica at the edges of the field. Keeping the Moon at the bottom edge of the field, I could compensate a bit by refocusing the Papilio to make the image of the Moon more presentable, but  alas, ruddy Mars had ballooned in size at the opposite side of the field. In comparison, the Leica image was much more together, indicating that its field of view was flatter overall and better corrected.

In addition, I judged the contrast to be significantly better in the Leica than in the Papilio. Indeed, of all the roof prism binoculars I have tested(with the possible exception of a Swarovski 10 x 42 EL Range), the Leica consistently produces the best contrast when viewing the Moon. Time and time again, the lunar vistas served up by this tiny binocular are quite simply breathtaking and have to be seen to be believed!

So, once again, the Leica pulled ahead in this rather severe test. Leica engineers have designed good field flattening lenses for the Trinovids which guarantee better edge of field correction than that exhibited in many other models. Indeed, truth be told, the Leica has edge of field performance up there with the best roof prism binoculars I have so far tested.


One of the issues some binocular enthusiasts have with the Leica Trinovid 8 x 20 pertains to its small size. It is true that this glass can be quite fiddly to set the correct IPD and exact pupil position when glassing. This is much easier to achieve with the Papilios. That said, since I tend to keep the Leica eyecups in the extended position, it increases its overall physical size and so makes it easier to handle when taking out of and placing it back into its case for storage. The Leica has a very fine focusing wheel but it’s rather on the small side so could prove tricky to operate, especially in winter, when using gloves. The Pentax Papilio II, in comparison, is much easier to handle owing to its larger size which fits my hands better. What’s more, the larger focus wheel is considerably easier to negotiate even with gloves on. Indeed, one of the greatest virtues of the Pentax Papilio binoculars is the large, silky smooth focusing wheel on both models which is essential for bringing objects into focus rapidly from extreme close-up right out to infinity.

The dioptre setting on the Leica is located on the right objective. It cannot be locked in place but does hold its position firmly for many months if not disturbed. Indeed, I have never needed to adjust it since I first acquired the instrument earlier this year. In contrast, the dioptre setting on the Pentax Papilio II is located in a ring under the right ocular. It too can be adjusted by twisting the ring but it has neat little click stops that keep it firmly in place without you ever having to worry about. As I said when reviewing the 6.5x Papilio II, this is a very clever engineering solution applied to great effect on this low-cost binocular!

The Leica glass is better suited to changes in the weather however. Unlike the Papilio IIs, which are neither fog nor water proof, the Leica is filled with dry nitrogen to prevent fogging of the internal optical components in cold weather, which are therefore sealed off from the outside environment. The Leica is splash proof rather than fully waterproof, which means that it can be used in light rain or humid environments without worrying about the build up of internal moisture and, in the long term, fungal infestations. Indeed I have heard of glassers who have used the little Leica in the high humidity of tropical rain forests for weeks and months on end, where they have reported flawless performance from this tiny glass.

Additionally, the Leica binocular has special ‘Aquadura’ -like coatings applied to the outside lens elements to repel water droplets and dust, as well as dissipating fog accidentally built up on the lenses should the user breathe on the oculars or objectives during cold weather applications. The Papilio IIs do not have these coating technologies.

Another notable difference between both glasses pertains to their ability to be mounted to a tripod. The Leica has no such facility but the Papilio II can easily be mated to such stabilising devices.


A few weeks experience with both Papilios has proven to be very instructive. Indeed, it has forced me to radically re-think the pocket binoculars I now wish to use going forward. In my opinion, the Pentax Papilio II 6.5 x 21 is the gem of the pair. While I would rate the 8.5x as good, the 6.5x is excellent! Indeed my tests have convinced me that I could do without my Zeiss Terra 8 x 25 ED. The Pentax Papilio II 6.5 x 21 has taken its place because it offers me the same comfortable viewing experience, an even wider field of view (7.5 degrees vs 6.8 degrees) and also doubles up as an excellent field microscope when I need it, with its incredible close focus(0.5m). In fact, the entire episode triggered a selling off of a whole string of models I had recently acquired, as I don’t like hoarding equipment. The Zeiss was a very sweet instrument, and everything I have said about it still holds true, but I simply couldn’t justify holding onto two premium models in the pocket size range after my experiences with the Papilio 6.5 x 21. The latter has turned out to be a more versatile than any 8 x 25! The Zeiss went for a good price( it has excellent re-sale value) and to a good home!

My younger son, Douglas, has expressed a particular interest in the 6.5 x Papilio and has been caught hogging it and showing it off to his pals, so I decided to let him have it on the proviso that he look after it properly and I can borrow it from time to time. Now everyone in the family has a pocket or compact binocular!

The Leica Trinovid 8 x 20 has now become my instrument of choice as a general purpose pocket glass for travel and leisure. At first I treated it as somewhat of an ‘expensive toy’ that was more a curiosity than anything else, but after a while that preyed on my conscience. The Leica was designed to be used and used hard in the field. It was not designed to be an ornament or to be pampered inside a glass case.  By using it extensively in the field for hours on end, I have finally come to grips with its small exit pupil and I no longer experience any blackouts with it as I had experienced when I first used it some months back. And though the Trinovid is an expensive piece of kit as pocket glasses go, it will serve me well for decades. How do I know this? Well, check out this recent youtube review from a chap who owned and used a Leitz (the older name for Leica)10 x 25 Trinovid since the 1970s, but who recently treated himself to the newer Leica Ultravid 8 x 20.  If it served him well over all those decades since the 1970s, I figured mine would as well!

OK, time to wrap this blog up.  Thanks for reading!


Writers also need to eat, so if you like these reviews please consider making a purchase of one of my books. Thank you!


De Fideli.

12 thoughts on “Thoughts on the Pentax Papilio II 8.5 x 21 Binocular.

  1. Thanks for the great review. I am in the market for some pocket glass and unfortunately, my budget leans more to the $ than the $$$$ side. My concern for the Papilio owes to my intended use. It will be kept in my vest when fly fishing to spot bugs on the water and fish feeding downstream. Humidity may be an issue and I have been known to wade ‘deep’. The lack of weatherproofing is what is holding me back from the purchase. I have considered some of the small ATB Nikon and Pentax/Olympus WP binns. Any thoughts or suggestions? Thanks again…cheers.

  2. Hello David,

    Thanks for your message.

    The Papilio binocular is just unbeatable when it comes to getting wonderful close-ups of insects down to about 0.5m. But as you point out, it lacks waterproofing. If that extreme close focus is important to you, then you have little option than to use the Papilio. I would just carry it high on your chest if wading in deep by keeping the strap short.
    Failing that, there are a number of other options that might work well for you if you can tolerate less close minimal focusing. One option is the Kowa SV 8x 25 which is waterproof and focuses down to 1.5m or less. It has decent optics too, especially for its modest price. It has a dual hinge design so folds into a pocketable format for easy storage and weighs about 260g:×25-compact-binoculars.html
    Another option is the Opticron Aspheric 3 8 x 25 which is pretty much the same format as the Kowa but has better optics and focuses down to 2m or less. Weight is under 300g. It is also waterproof but costs about 50 per cent more×25-compact-binoculars.html

    Another similar option is the the Pentax AD 8x 25 WP for about the same price as the Opticron. Build quality looks as good as the Opticron for about the same price:×25-wp.509/

    If you can tolerate slightly larger models, I would also seriously consider the Prostaff 7S 8x 30; a very fine binocular for its modest cost (~£140).

    I’m also about to test out the Vortex Diamondback HD 8x 28 which retails for about £135. Both weigh about 500g, have full waterproofing and decent close focus( 1.8 -2m).

    Sorry to bombard you with options but hopefully it will give you some ideas.

    Good luck with your shopping!

    With best wishes,


    • Thank you Neil for your reply!

      I am in USA so my options are somewhat different than yours.

      The Opticron you listed are hard to come by. The need for close focus is to see bugs on the water so I don’t have to be very very close. I think waterproof/fog proof is also important. I noticed an old pair of non waterproof bins are cooked due to humidity and splashes. I asked too much of them.

      I considered the Zeiss Terra ED 8×25 as it ticks all the boxes. Good eye relief for glasses but slightly more expensive than I had wanted to spend. Tempting.

      I handled the 8×20 ultravids but don’t want to go into debt but wow those were cool. Size is ideal.

      The Kowas are available here but have to be special ordered to be touched. Amazon prime may be my friend.

      I will keep you posted. Thanks David

  3. Hi David,

    The little Ultravid is an amazing instrument. I chose it over the 8x 32 Trinovid HD and two smaller Trinovid BCAs, all of which had to go in order to fund the purchase but it’s all done now- no regrets!

    Let us know how you get on with your choices.

    Best wishes,


  4. Hello,
    Thank you for your great review.
    You have compared the Ultravid 8×20 with the Trinovid 8×20..?
    Too much optical and mechanical difference ?
    Worth the Ultravid on the Trinovid for the price?
    Best Regards,

  5. Dear Paul,

    Many thanks for your message.

    I have owned and used both the Trinovid BCAs(8x and 10x) and the Ultravid BR 8 x 20.

    Both the Trinovid BCA 8x 20 and the Ultravid 8x 20 are very fine optics. Leica create and design some wonderful instruments and these two are no exception.

    I would say that the Ultravid is the better optic though. The effects are subtle but very real. The Ultravid has better contrast and a flatter field than the Trinovid and has better control of glare. If you are on a tight budget, get the Trinovid but if you can afford to save the extra cash, I would advise the Ultravid for sure. The Trinovid is excellent but the Ultravid is simply spectacular. Either one will give you many years of enjoyment as they are built to last.

    Hope that helps

    Best regards,


  6. Hello again Neil,

    Another great comparative post – and one well worth it! Thank you. As you say, many reviewers wouldn’t consider comparing an £80 binocular against a £400 benchmark – but it’s well worth doing so in the case of the Papilio and exposes that truth that less can sometimes mean more.

    I can also testify to the 6.5 being a gem. Nothing else has the ‘wow factor’ of its close focus. Quite literally, one often says ‘wow’ when focusing closely on a newly opened flower, a spider on the bathroom ceiling, the end of one’s own boot (cracked leather is a fascinating landscape to view!) But to then realise that the Papilio also functions as a competent long-range binocular as well completes the performance. An abiding Papilio memory will always be following a Sparrowhawk circling around and around, high above the houses where I live, looking out for a feathered morsel to chase. Such clear, bright views of this otherwise tiny bird hundreds of above my head when just a few minutes before I was examining a resplendent Peacock butterfly sunning itself on a wall just centimetres from my head. Every hair on its body, every scale on its wings visible in acute detail. Awesome. Glorious. A magnification of the Creation. And I didn’t have to back up a couple of metres to see it through the binocular!

    Admittedly, the Papilio is an instrument that requires careful handling – if you drop it, you’ll bust it; but looked after it more than rewards its user.

    Despite all the above I have to admit to having a soft spot for the Trinovid BCA. It’s one on my ‘to try’ list if I ever get the chance, just to see what it handles like.

    Its rugged aesthetic, its utility (‘…designed to be used and used hard…’) appeal to me as the owner of a larger Trinovid BN. To think of having that quality of optic in your shirt or trouser pocket is a pleasant idea – but as you say, in most circumstances you’re going to have the binocular round your neck ready for action rather than tucked away, so its space saving ability is a moot point when considering which binocular is ‘best’ in comparison to the Papilio’s size. Such small optical engineering though is a wonderful thing and Leica are to be well respected for having created such a binocular. It’s continuous production is testament to its brilliance. Perhaps I could convince a relative to get me one of my next Significant Birthday?

    Thanks again for your time and consideration in comparing and contrasting binoculars. Your blogs are really good to read (and re-read, especially your ‘Adventures’) and bring to mind lots of one’s own experiences of life through the lens.

    Keep writing and God bless you.

  7. Hello James,

    Many thanks for that; it means a lot to me that folk get something out of my work.

    Thanks also for your testimony regarding the Papilios. They are both great bargains and enjoyed by many outdoor enthusiasts. I think you will really love the little Trinovid BCA 8 x 20. Leica make some fine gear and it will surely complement your BN.

    I’m pretty much at the end of my exploration of the world of binoculars, with only a few more models to test. I’ve pretty much seen everything there is to see . Hope to begin more blogs on my experiences thereafter.

    God bless,


  8. Just one more question Neil, based on your experience of the Trinovid BCA 8 x 20 and Papilios:

    Is the Trinovid much more robust than the Papilio? I know that roof prisms are known for being more ‘shock proof’ than porros but I wonder if the BCA’s diminutive size means that it needs more gentle handling than a mid-sized roof prism binocular (such as the BN)?

    I am the Klutz of the family and delicate tools don’t last long around me (hence my reservations about the Papilio’s size and apparent fragility out in the field). For as long as I’ve had the Papilio I’ve always taken extra steps to ensure its safety which sometimes means it’s used less than I think a more robust pocket binocular could be. The Papilio is mostly for close-focus in the garden. Whereas I can’t imagine taking it out for an ‘adventure’, which is what I’m currently daydreaming about regards the BCA!

    Your experienced opinion is once again very welcome as I’m sure a shop wouldn’t let me borrow a BCA for a day’s trialling!

  9. Hello James,

    Roof prism binos in general are a little bit more robust than porro prism designs because everything is internalised within the chassis. The Trinovid BCA is a pocket binocular. and so will be small in your hands. It takes a little practice swinging out those barrels to get your preferred IPD.

    The great thing about the Trinovid BCA is its pocket, so if you encounter rain, you can simply pop it inside your pocket, keeping it dry. The Trinovid is advertised as splash proof, so it should handle light rain OK, so long as you dry off the outside as soon as you can.

    I think you’ll really like the little BCA. It has oodles of charm!

    Hope that helps.


  10. Guten Morgen. Ich stiess bei der Suche nach Rezensionen auf ihren Bericht und bestellte gestützt auf die Argumentation das Pentax Papilio 6.5. Ich bedanke mich und schreibe diese kurze Antwort, um sie zu motivieren, weiterhin zu publizieren. Dank der immer besseren Übersetzungs-Software, werden ihre Rezensionen vermutlich weltweit gelesen. Gruss aus der Schweiz.


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